summaryrefslogtreecommitdiffstats
path: root/x11vnc/README
diff options
context:
space:
mode:
Diffstat (limited to 'x11vnc/README')
-rw-r--r--x11vnc/README18246
1 files changed, 0 insertions, 18246 deletions
diff --git a/x11vnc/README b/x11vnc/README
deleted file mode 100644
index e8457e6..0000000
--- a/x11vnc/README
+++ /dev/null
@@ -1,18246 +0,0 @@
-
-Copyright (C) 2002-2010 Karl J. Runge <runge@karlrunge.com>
-All rights reserved.
-
-x11vnc README file Date: Mon Dec 27 20:58:57 EST 2010
-
-The following information is taken from these URLs:
-
- http://www.karlrunge.com/x11vnc/index.html
- http://www.karlrunge.com/x11vnc/x11vnc_opts.html
- ...
-
-they contain the most up to date info.
-
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/index.html:
-
-
- _________________________________________________________________
-
-x11vnc: a VNC server for real X displays
- (to FAQ) (to Downloads) (to Building) (to Beta Test)
- (to Donations) [PayPal]
-
- x11vnc allows one to view remotely and interact with real X displays
- (i.e. a display corresponding to a physical monitor, keyboard, and
- mouse) with any VNC viewer. In this way it plays the role for Unix/X11
- that WinVNC plays for Windows.
-
- It has built-in SSL/TLS encryption and 2048 bit RSA authentication,
- including VeNCrypt support; UNIX account and password login support;
- server-side scaling; single port HTTPS/HTTP+VNC; Zeroconf service
- advertising; and TightVNC and UltraVNC file-transfer. It has also been
- extended to work with non-X devices: natively on Mac OS X Aqua/Quartz,
- webcams and TV tuner capture devices, and embedded Linux systems such
- as Qtopia Core. Full IPv6 support is provided. More features are
- described here.
-
- It also provides an encrypted Terminal Services mode (-create, -svc,
- or -xdmsvc options) based on Unix usernames and Unix passwords where
- the user does not need to memorize his VNC display/port number.
- Normally a virtual X session (Xvfb) is created for each user, but it
- also works with X sessions on physical hardware. See the tsvnc
- terminal services mode of the SSVNC viewer for one way to take
- advantage of this mode.
-
- I wrote x11vnc back in 2002 because x0rfbserver was basically
- impossible to build on Solaris and had poor performance. The primary
- x0rfbserver build problems centered around esoteric C++ toolkits.
- x11vnc is written in plain C and needs only standard libraries and so
- should work on nearly all Unixes, even very old ones. I also created
- enhancements to improve the interactive response, added many features,
- and etc.
-
- This page including the FAQ contains much information [*]; solutions
- to many problems; and interesting applications, but nevertheless
- please feel free to contact me if you have problems or questions (and
- if I save you time or expense by giving you some of my time, please
- consider a PayPal Donation.) Do check the FAQ and this page first; I
- realize the pages are massive, but you can often use your browser's
- find-in-page search action using a keyword to find the answer to your
- problem or question.
-
- SSVNC: An x11vnc side-project provides an Enhanced TightVNC Viewer
- package (SSVNC) for Unix, Windows, and Mac OS X with automatic SSL
- and/or SSH tunnelling support, SSL Certificate creation, Saved
- connection profiles, Zeroconf, VeNCrypt, and built-in Proxy support.
- Added features for the TightVNC Unix viewer: NewFBSize, ZRLE encoding,
- Viewer-side Scaling, cursor alphablending, low color modes, and
- enhanced popup menu; UltraVNC extensions support for: File Transfer,
- Text Chat, Single Window, Server Input, and 1/n Scaling extensions,
- and UltraVNC DSM encryption. The SSVNC bundle could be placed on, say,
- a USB memory stick for SSL/SSH VNC viewing from nearly any networked
- computer.
-
- _________________________________________________________________
-
- Announcements:
-
- Important: If you created any permanent SSL certificates (e.g. via
- "x11vnc -ssl SAVE ...") on a Debian or Ubuntu system from Sept. 2006
- through May 2008, then those keys are likely extremely weak and can be
- easily cracked. The certificate files should be deleted and recreated
- on a non-Debian system or an updated one. See
- http://www.debian.org/security/2008/dsa-1571 for details. The same
- applies to SSH keys (not used by x11vnc directly, but many people use
- SSH tunnels for VNC access.)
-
- FAQ moved: The huge FAQ has finally been moved to its own page. If you
- are trying to follow someone's link to an FAQ once on this page it is
- now a broken link. Try inserting the string "faq.html", e.g.:
-from: http://www.karlrunge.com/x11vnc/#faq-singleclick
-to: http://www.karlrunge.com/x11vnc/faq.html#faq-singleclick
-
- Apologies for the inconvenience, unfortunately it is not possible to
- automatically redirect to the new page since the '#' anchor is not
- sent to the webserver.
-
- _________________________________________________________________
-
- Background:
-
- VNC (Virtual Network Computing) is a very useful network graphics
- protocol (applications running on one computer but displaying their
- windows on another) in the spirit of X, however, unlike X, the
- viewing-end is very simple and maintains no state. It is a remote
- framebuffer (RFB) protocol.
-
- Some VNC links:
- * http://www.realvnc.com
- * http://www.tightvnc.com
- * http://www.ultravnc.com/
- * http://www.testplant.com/products/vine_server/OS_X
-
- For Unix, the traditional VNC implementation includes a "virtual" X11
- server Xvnc (usually launched via the vncserver command) that is not
- associated with a physical display, but provides a "fake" one X11
- clients (xterm, firefox, etc.) can attach to. A remote user then
- connects to Xvnc via the VNC client vncviewer from anywhere on the
- network to view and interact with the whole virtual X11 desktop.
-
- The VNC protocol is in most cases better suited for remote connections
- with low bandwidth and high latency than is the X11 protocol because
- it involves far fewer "roundtrips" (an exception is the cached pixmap
- data on the viewing-end provided by X.) Also, with no state maintained
- the viewing-end can crash, be rebooted, or relocated and the
- applications and desktop continue running. Not so with X11.
-
- So the standard Xvnc/vncserver program is very useful, I use it for
- things like:
- * Desktop conferencing with other users (e.g. code reviews.)
- * Long running apps/tasks I want to be able to view from many places
- (e.g. from home and work.)
- * Motif, GNOME, and similar applications that would yield very poor
- performance over a high latency link.
-
- However, sometimes one wants to connect to a real X11 display (i.e.
- one attached to a physical monitor, keyboard, and mouse: a Workstation
- or a SunRay session) from far away. Maybe you want to close down an
- application cleanly rather than using kill, or want to work a bit in
- an already running application, or would like to help a distant
- colleague solve a problem with their desktop, or would just like to
- work out on the deck for a while. This is where x11vnc is useful.
- _________________________________________________________________
-
- How to use x11vnc:
-
- In this basic example let's assume the remote machine with the X
- display you wish to view is "far-away.east:0" and the workstation you
- are presently working at is "sitting-here.west".
-
- Step 0. Download x11vnc (see below) and have it available to run on
- far-away.east (on some linux distros it is as easy as "apt-get install
- x11vnc", "emerge x11vnc", etc.) Similarly, have a VNC viewer (e.g.
- vncviewer) ready to run on sitting-here.west. We recommend TightVNC
- Viewers (see also our SSVNC viewer.)
-
- Step 1. By some means log in to far-away.east and get a command shell
- running there. You can use ssh, or even rlogin, telnet, or any other
- method to do this. We do this because the x11vnc process needs to be
- run on the same machine the X server process is running on (otherwise
- things would be extremely slow.)
-
- Step 2. In that far-away.east shell (with command prompt "far-away>"
- in this example) run x11vnc directed at the far-away.east X session
- display:
-
- far-away> x11vnc -display :0
-
- You could have also set the environment variable DISPLAY=:0 instead of
- using "-display :0". This step attaches x11vnc to the far-away.east:0
- X display (i.e. no viewer clients yet.)
-
- Common Gotcha: To get X11 permissions right, you may also need to set
- the XAUTHORITY environment variable (or use the -auth option) to point
- to the correct MIT-MAGIC-COOKIE file (e.g. /home/joe/.Xauthority.) If
- x11vnc does not have the authority to connect to the display it exits
- immediately. More on how to fix this below.
-
- If you suspect an X11 permissions problem do this simple test: while
- sitting at the physical X display open a terminal window
- (gnome-terminal, xterm, etc.) You should be able to run x11vnc
- successfully in that terminal without any need for command line
- options. If that works OK then you know X11 permissions are the only
- thing preventing it from working when you try to start x11vnc via a
- remote shell. Then fix this with the tips below.
-
- Note as of Feb/2007 you can also try the -find option instead of
- "-display ..." and see if that finds your display and Xauthority. Note
- as of Dec/2009 the -findauth and "-auth guess" options may be helpful
- as well.
- (End of Common Gotcha)
-
- When x11vnc starts up there will then be much chatter printed out (use
- "-q" to quiet it), until it finally says something like:
- .
- .
- 13/05/2004 14:59:54 Autoprobing selected port 5900
- 13/05/2004 14:59:54 screen setup finished.
- 13/05/2004 14:59:54
- 13/05/2004 14:59:54 The VNC desktop is far-away:0
- PORT=5900
-
- which means all is OK, and we are ready for the final step.
-
- Step 3. At the place where you are sitting (sitting-here.west in this
- example) you now want to run a VNC viewer program. There are VNC
- viewers for Unix, Windows, MacOS, Java-enabled web browsers, and even
- for PDA's like the Palm Pilot and Cell Phones! You can use any of them
- to connect to x11vnc (see the above VNC links under "Background:" on
- how to obtain a viewer for your platform or see this FAQ. For Solaris,
- vncviewer is available in the Companion CD package SFWvnc.)
-
- In this example we'll use the Unix vncviewer program on sitting-here
- by typing the following command in a second terminal window:
-
- sitting-here> vncviewer far-away.east:0
-
- That should pop up a viewer window on sitting-here.west showing and
- allowing interaction with the far-away.east:0 X11 desktop. Pretty
- nifty! When finished, exit the viewer: the remote x11vnc process will
- shutdown automatically (or you can use the -forever option to have it
- wait for additional viewer connections.)
-
- Common Gotcha: Nowadays there will likely be a host-level firewall on
- the x11vnc side that is blocking remote access to the VNC port (e.g.
- 5900.) You will either have to open up that port (or a range of ports)
- in your firewall administration tool, or try the SSH tunnelling method
- below (even still the firewall must allow in the SSH port, 22.)
-
-
- Shortcut: Of course if you left x11vnc running on far-away.east:0 in a
- terminal window with the -forever option or as a service, you'd only
- have to do Step 3 as you moved around. Be sure to use a VNC Password
- or other measures if you do that.
-
-
- Super Shortcut: Here is a potentially very easy way to get all of it
- working.
- * Have x11vnc (0.9.3 or later) available to run on the remote host
- (i.e. in $PATH.)
- * Download and unpack a SSVNC bundle (1.0.19 or later, e.g.
- ssvnc_no_windows-1.0.28.tar.gz) on the Viewer-side machine.
- * Start the SSVNC Terminal Services mode GUI: ./ssvnc/bin/tsvnc
- * Enter your remote username@hostname (e.g. fred@far-away.east) in
- the "VNC Terminal Server" entry.
- * Click "Connect".
-
- That will do an SSH to username@hostname and start up x11vnc and then
- connect a VNC Viewer through the SSH encrypted tunnel.
-
- There are a number of things assumed here, first that you are able to
- SSH into the remote host; i.e. that you have a Unix account there and
- the SSH server is running. On Unix and MacOS X it is assumed that the
- ssh client command is available on the local machine (on Windows a
- plink binary is included in the SSVNC bundle.) Finally, it is assumed
- that you are already logged into an X session on the remote machine,
- e.g. your workstation (otherwise, a virtual X server, e.g. Xvfb, will
- be started for you.)
-
- In some cases the remote SSH server will not run commands with the
- same $PATH that you normally have in your shell there. In this case
- click on Options -> Advanced -> X11VNC Options, and type in the
- location of the x11vnc binary under "Full Path". (End of Super
- Shortcut)
-
-
- Desktop Sharing: The above more or less assumed nobody was sitting at
- the workstation display "far-away.east:0". This is often the case: a
- user wants to access her workstation remotely. Another usage pattern
- has the user sitting at "far-away.east:0" and invites one or more
- other people to view and interact with his desktop. Perhaps the user
- gives a demo or presentation this way (using the telephone for vocal
- communication.) A "Remote Help Desk" mode would be similar: a
- technician connects remotely to the user's desktop to interactively
- solve a problem the user is having.
-
- For these cases it should be obvious how it is done. The above steps
- will work, but more easily the user sitting at far-away.east:0 simply
- starts up x11vnc from a terminal window, after which the guests would
- start their VNC viewers. For this usage mode the "-connect
- host1,host2" option may be of use to automatically connect to the
- vncviewers in "-listen" mode on the list of hosts.
- _________________________________________________________________
-
- Tunnelling x11vnc via SSH:
-
- The above example had no security or privacy at all. When logging into
- remote machines (certainly when going over the internet) it is best to
- use ssh, or use a VPN (for a VPN, Virtual Private Network, the above
- example should be pretty safe.)
-
- For x11vnc one can tunnel the VNC protocol through an encrypted ssh
- channel. It would look something like running the following commands:
- sitting-here> ssh -t -L 5900:localhost:5900 far-away.east 'x11vnc -localhost
--display :0'
-
- (you will likely have to provide passwords/passphrases to login from
- sitting-here into your far-away.east Unix account; we assume you have
- a login account on far-away.east and it is running the SSH server)
-
- And then in another terminal window on sitting-here run the command:
- sitting-here> vncviewer -encodings "copyrect tight zrle hextile" localhost:0
-
- Note: The -encodings option is very important: vncviewer will often
- default to "raw" encoding if it thinks the connection is to the local
- machine, and so vncviewer gets tricked this way by the ssh
- redirection. "raw" encoding will be extremely slow over a networked
- link, so you need to force the issue with -encodings "copyrect tight
- ...". Nowadays, not all viewers use the -encodings option, try
- "-PreferredEncoding=ZRLE" (although the newer viewers seem to
- autodetect well when to use raw or not.)
-
- Note that "x11vnc -localhost ..." limits incoming vncviewer
- connections to only those from the same machine. This is very natural
- for ssh tunnelling (the redirection appears to come from the same
- machine.) Use of a VNC password is also strongly recommended.
-
- Note also the -t we used above (force allocate pseudoterminal), it
- actually seems to improve interactive typing response via VNC!
-
- You may want to add the -C option to ssh to enable compression. The
- VNC compression is not perfect, and so this may help a bit. However,
- over a fast LAN you probably don't want to enable SSH compression
- because it can slow things down. Try both and see which is faster.
-
- If your username is different on the remote machine use something
- like: "fred@far-away.east" in the above ssh command line.
-
- Some VNC viewers will do the ssh tunnelling for you automatically, the
- TightVNC Unix vncviewer does this when the "-via far-away.east" option
- is supplied to it (this requires x11vnc to be already running on
- far-away.east or having it started by inetd(8).) See the 3rd script
- example below for more info.
-
- SSVNC: You may also want to look at the Enhanced TightVNC Viewer
- (ssvnc) bundles because they contain scripts and GUIs to automatically
- set up SSH tunnels (e.g. the GUI, "ssvnc", does it automatically and
- so does this command: "ssvnc_cmd -ssh user@far-away.east:0") and can
- even start up x11vnc as well.
-
- The Terminal Services mode of SSVNC is perhaps the easiest way to use
- x11vnc. You just need to have x11vnc available in $PATH on the remote
- side (and can SSH to the host), and then on the viewer-side you type
- something like:
- tsvnc fred@far-away.east
-
- everything else is done automatically for you. Normally this will
- start a virtual Terminal Services X session (RAM-only), but if you
- already have a real X session up on the physical hardware it will find
- that one for you.
-
- Gateways: If the machine you SSH into is not the same machine with
- the X display you wish to view (e.g. your company provides incoming
- SSH access to a gateway machine), then you need to change the above
- to, e.g.: "-L 5900:OtherHost:5900":
- sitting-here> ssh -t -L 5900:OtherHost:5900 gateway.east
-
- Where gateway.east is the internet hostname (or IP) of the gateway
- machine (SSH server.) 'OtherHost' might be, e.g., freds-pc or
- 192.168.2.33 (it is OK for these to be private hostnames or private IP
- addresses, the host in -L is relative to the remote server side.)
-
- Once logged in, you'll need to do a second login (ssh, rsh, etc.) to
- the workstation machine 'OtherHost' and then start up x11vnc on it (if
- it isn't already running.) (The "-connect gateway:59xx" option may be
- another alternative here with the viewer already in -listen mode.) For
- an automatic way to use a gateway and have all the network traffic
- encrypted (including inside the firewall) see Chaining SSH's.
-
- These gateway access modes also can be done automatically for you via
- the "Proxy/Gateway" setting in SSVNC (including the Chaining SSH's
- case, "Double Proxy".)
-
- Firewalls/Routers:
-
- A lot of people have inexpensive devices for home or office that act
- as a Firewall and Router to the machines inside on a private LAN. One
- can usually configure the Firewall/Router from inside the LAN via a
- web browser.
-
- Often having a Firewall/Router sitting between the vncviewer and
- x11vnc will make it impossible for the viewer to connect to x11vnc.
-
- One thing that can be done is to redirect a port on the
- Firewall/Router to, say, the SSH port (22) on an inside machine (how
- to do this depends on your particular Firewall/Router, often the
- router config URL is http://192.168.100.1 See www.portforward.com for
- more info.) This way you reach these computers from anywhere on the
- Internet and use x11vnc to view X sessions running on them.
-
- Suppose you configured the Firewall/Router to redirect these ports to
- two internal machines:
- Port 12300 -> 192.168.1.3, Port 22 (SSH)
- Port 12301 -> 192.168.1.4, Port 22 (SSH)
-
- (where 192.168.1.3 is "jills-pc" and 192.168.1.4 is "freds-pc".) Then
- the ssh's would look something like:
- sitting-here> ssh -t -p 12300 -L 5900:localhost:5900 jill@far-away.east 'x11v
-nc -localhost -display :0'
- sitting-here> ssh -t -p 12301 -L 5900:localhost:5900 fred@far-away.east 'x11v
-nc -localhost -display :0'
-
- Where far-away.east means the hostname (or IP) that the
- Router/Firewall is using (for home setups this is usually the IP
- gotten from your ISP via DHCP, the site http://www.whatismyip.com/ is
- a convenient way to determine what it is.)
-
- It is a good idea to add some obscurity to accessing your system via
- SSH by using some high random port (e.g. 12300 in the above example.)
- If you can't remember it, or are otherwise not worried about port
- scanners detecting the presence of your SSH server and there is just
- one internal PC involved you could map 22:
- Port 22 -> 192.168.1.3, Port 22 (SSH)
-
- Again, this SSH gateway access can be done automatically for you via
- the "Proxy/Gateway" setting in SSVNC. And under the "Remote SSH
- Command" setting you can enter the x11vnc -localhost -display :0.
-
- Host-Level-Firewalls: even with the hardware Firewall/Router problem
- solved via a port redirection, most PC systems have their own Host
- level "firewalls" enabled to protect users from themselves. I.e. the
- system itself blocks all incoming connections. So you will need to see
- what is needed to configure it to allow in the port (e.g. 22) that you
- desire. E.g. Yast, Firestarter, iptables(1), etc..
-
- VNC Ports and Firewalls: The above discussion was for configuring the
- Firewall/Router to let in port 22 (SSH), but the same thing can be
- done for the default VNC port 5900:
- Port 5900 -> 192.168.1.3, Port 5900 (VNC)
- Port 5901 -> 192.168.1.4, Port 5900 (VNC)
-
- (where 192.168.1.3 is "jills-pc" and 192.168.1.4 is "freds-pc".) This
- could be used for normal, unencrypted connections and also for SSL
- encrypted ones.
-
- The VNC displays to enter in the VNC viewer would be, say,
- "far-away.east:0" to reach jills-pc and "far-away.east:1" to reach
- freds-pc. We assume above that x11vnc is using port 5900 (and any
- Host-Level-firewalls on jills-pc has been configured to let that port
- in.) Use the "-rfbport" option to tell which port x11vnc should listen
- on.
-
- For a home system one likely does not have a hostname and would have
- to use the IP address, say, "24.56.78.93:0". E.g.:
- vncviewer 24.56.78.93:0
-
- You may want to choose a more obscure port on the router side, e.g.
- 5944, to avoid a lot of port scans finding your VNC server. For 5944
- you would tell the viewer to use:
- vncviewer 24.56.78.93:44
-
- The IP address would need to be communicated to the person running the
- VNC Viewer. The site http://www.whatismyip.com/ can help here.
-
- _________________________________________________________________
-
- Scripts to automate ssh tunneling: As discussed below, there may be
- some problems with port 5900 being available. If that happens, the
- above port and display numbers may change a bit (e.g. -> 5901 and :1).
- However, if you "know" port 5900 will be free on the local and remote
- machines, you can easily automate the above two steps by using the
- x11vnc option -bg (forks into background after connection to the
- display is set up) or using the -f option of ssh. Some example scripts
- are shown below. Feel free to try the ssh -C to enable its compression
- and see if that speeds things up noticeably.
- _________________________________________________________________
-
- #1. A simple example script, assuming no problems with port 5900 being
- taken on the local or remote sides, looks like:
-#!/bin/sh
-# usage: x11vnc_ssh <host>:<xdisplay>
-# e.g.: x11vnc_ssh snoopy.peanuts.com:0
-# (user@host:N also works)
-
-host=`echo $1 | awk -F: '{print $1}'`
-disp=`echo $1 | awk -F: '{print $2}'`
-if [ "x$disp" = "x" ]; then disp=0; fi
-
-cmd="x11vnc -display :$disp -localhost -rfbauth .vnc/passwd"
-enc="copyrect tight zrle hextile zlib corre rre raw"
-
-ssh -f -t -L 5900:localhost:5900 $host "$cmd"
-
-for i in 1 2 3
-do
- sleep 2
- if vncviewer -encodings "$enc" :0; then break; fi
-done
-
- See also rx11vnc.pl below.
- _________________________________________________________________
-
- #2. Another method is to start the VNC viewer in listen mode
- "vncviewer -listen" and have x11vnc initiate a reverse connection
- using the -connect option:
-#!/bin/sh
-# usage: x11vnc_ssh <host>:<xdisplay>
-# e.g.: x11vnc_ssh snoopy.peanuts.com:0
-# (user@host:N also works)
-
-host=`echo $1 | awk -F: '{print $1}'`
-disp=`echo $1 | awk -F: '{print $2}'`
-if [ "x$disp" = "x" ]; then disp=0; fi
-
-cmd="x11vnc -display :$disp -localhost -connect localhost" # <== note new opt
-ion
-enc="copyrect tight zrle hextile zlib corre rre raw"
-
-vncviewer -encodings "$enc" -listen &
-pid=$!
-ssh -t -R 5500:localhost:5500 $host "$cmd"
-kill $pid
-
- Note the use of the ssh option "-R" instead of "-L" to set up a remote
- port redirection.
- _________________________________________________________________
-
- #3. A third way is specific to the TightVNC vncviewer special option
- -via for gateways. The only tricky part is we need to start up x11vnc
- and give it some time (5 seconds in this example) to start listening
- for connections (so we cannot use the TightVNC default setting for
- VNC_VIA_CMD):
-#!/bin/sh
-# usage: x11vnc_ssh <host>:<xdisplay>
-# e.g.: x11vnc_ssh snoopy.peanuts.com:0
-
-host=`echo $1 | awk -F: '{print $1}'`
-disp=`echo $1 | awk -F: '{print $2}'`
-if [ "x$disp" = "x" ]; then disp=0; fi
-
-VNC_VIA_CMD="ssh -f -t -L %L:%H:%R %G x11vnc -localhost -rfbport 5900 -display
-:$disp; sleep 5"
-export VNC_VIA_CMD
-
-vncviewer -via $host localhost:0 # must be TightVNC vncviewer.
-
- Of course if you already have the x11vnc running waiting for
- connections (or have it started out of inetd(8)), you can simply use
- the TightVNC "vncviewer -via gateway host:port" in its default mode to
- provide secure ssh tunnelling.
- _________________________________________________________________
-
-
-
- VNC password file: Also note in the #1. example script that the option
- "-rfbauth .vnc/passwd" provides additional protection by requiring a
- VNC password for every VNC viewer that connects. The vncpasswd or
- storepasswd programs, or the x11vnc -storepasswd option can be used to
- create the password file. x11vnc also has the slightly less secure
- -passwdfile and "-passwd XXXXX" options to specify passwords.
-
- Very Important: It is up to YOU to tell x11vnc to use password
- protection (-rfbauth or -passwdfile), it will NOT do it for you
- automatically or force you to (use -usepw if you want to be forced
- to.) The same goes for encrypting the channel between the viewer and
- x11vnc: it is up to you to use ssh, stunnel, -ssl mode, a VPN, etc.
- (use the Enhanced TightVNC Viewer (SSVNC) GUI if you want to be forced
- to use SSL or SSH.) For additional safety, also look into the -allow
- and -localhost options and building x11vnc with tcp_wrappers support
- to limit host access.
-
- _________________________________________________________________
-
- Tunnelling x11vnc via SSL/TLS:
-
- One can also encrypt the VNC traffic using an SSL/TLS tunnel such as
- stunnel.mirt.net (also stunnel.org) or using the built-in (Mar/2006)
- -ssl openssl mode. A SSL-enabled Java applet VNC Viewer is also
- provided in the x11vnc package (and https can be used to download it.)
-
- Although not as ubiquitous as ssh, SSL tunnelling still provides a
- useful alternative. See this FAQ on -ssl and -stunnel modes for
- details and examples.
-
- The Enhanced TightVNC Viewer (SSVNC) bundles contain some convenient
- utilities to automatically set up an SSL tunnel from the viewer-side
- (i.e. to connect to "x11vnc -ssl ...".) And many other enhancements
- too.
- _________________________________________________________________
-
- Downloading x11vnc:
-
- x11vnc is a contributed program to the LibVNCServer project at
- SourceForge.net. I use libvncserver for all of the VNC aspects; I
- couldn't have done without it. The full source code may be found and
- downloaded (either file-release tarball or GIT tree) from the above
- link. As of Sep 2010, the x11vnc-0.9.12.tar.gz source package is
- released (recommended download). The x11vnc 0.9.12 release notes.
-
- The x11vnc package is the subset of the libvncserver package needed to
- build the x11vnc program. Also, you can get a copy of my latest,
- bleeding edge x11vnc-0.9.13-dev.tar.gz tarball to build the most up to
- date one.
-
- Precompiled Binaries/Packages: See the FAQ below for information
- about where you might obtain a precompiled x11vnc binary from 3rd
- parties and some ones I create.
-
- VNC Viewers: To obtain VNC viewers for the viewing side (Windows, Mac
- OS, or Unix) try these links:
- * http://www.tightvnc.com/download.html
- * http://www.realvnc.com/download-free.html
- * http://sourceforge.net/projects/cotvnc/
- * http://www.ultravnc.com/
- * Our Enhanced TightVNC Viewer (SSVNC)
-
- [ssvnc.gif]
-
-
- More tools: Here is a ssh/rsh wrapper script rx11vnc that attempts to
- automatically do the above Steps 1-3 for you (provided you have
- ssh/rsh login permission on the machine x11vnc is to be run on.) The
- above example would be: "rx11vnc far-away.east:0" typed into a shell
- on sitting-here.west. Also included is an experimental script
- rx11vnc.pl that attempts to tunnel the vnc traffic through an ssh port
- redirection (and does not assume port 5900 is free.) Have a look at
- them to see what they do and customize as needed:
- * rx11vnc wrapper script
- * rx11vnc.pl wrapper script to tunnel traffic thru ssh
-
- _________________________________________________________________
-
- Building x11vnc:
-
- Make sure you have all the needed build/compile/development packages
- installed (e.g. Linux distributions foolishly don't install them by
- default.) See this build FAQ for more details.
-
- If your OS has libjpeg.so and libz.so in standard locations you can
- build as follows (example given for the 0.9.12 release of x11vnc:
- replace with the version you downloaded):
-(un-tar the x11vnc+libvncserver tarball)
-# gzip -dc x11vnc-0.9.12.tar.gz | tar -xvf -
-
-(cd to the source directory)
-# cd x11vnc-0.9.12
-
-(run configure and then run make)
-# ./configure
-# make
-
-(if all went OK, copy x11vnc to the desired destination, e.g. $HOME/bin)
-# cp ./x11vnc/x11vnc $HOME/bin
-
- Or do make install, it will probably install to /usr/local/bin (run
- ./configure --help for information on customizing your configuration,
- e.g. --prefix=/my/place.) You can now run it via typing "x11vnc",
- "x11vnc -help | more", "x11vnc -forever -shared -display :0", etc.
-
-
- Note: Currently gcc is recommended to build libvncserver. In some
- cases it will build with non-gcc compilers, but the resulting binary
- sometimes fails to run properly. For Solaris pre-built gcc binaries
- are at http://www.sunfreeware.com/. Some Solaris pre-built x11vnc
- binaries are here.
-
- However, one user reports it does work fine when built with Sun Studio
- 10, so YMMV. In fact, here is a little build script to do this on
- Solaris 10:
-#!/bin/sh
-PATH=/usr/ccs/bin:/opt/SUNWspro/bin:$PATH; export PATH
-
-CC='cc' \
-CFLAGS='-xO4' \
-LDFLAGS='-L/usr/sfw/lib -L/usr/X11/lib -R/usr/sfw/lib -R/usr/X11/lib' \
-CPPFLAGS='-I /usr/sfw/include -I/usr/X11/include' \
-./configure
-
-MAKE="make -e"
-AM_CFLAGS=""
-export MAKE AM_CFLAGS
-$MAKE
-
- In general you can use the "make -e" trick if you don't like
- libvncserver's choice of AM_CFLAGS. See the build scripts below for
- more ideas. Scripts similar to the above have been shown to work with
- vendor C compilers on HP-UX (ccom: HP92453-01) and Tru64 (Compaq C
- V6.5-011.)
-
- You can find information on Misc. Build problems here.
-
- _________________________________________________________________
-
- Building on Solaris, FreeBSD, etc: Depending on your version of
- Solaris or other Unix OS the jpeg and/or zlib libraries may be in
- non-standard places (e.g. /usr/local, /usr/sfw, /opt/sfw, etc.)
-
- Note: If configure cannot find these two libraries then TightVNC and
- ZRLE encoding support will be disabled, and you don't want that!!! The
- TightVNC encoding gives very good compression and performance, it even
- makes a noticeable difference over a fast LAN.
-
-
- Shortcuts: On Solaris 10 you can pick up almost everything just by
- insuring that your PATH has /usr/sfw/bin (for gcc) and /usr/ccs/bin
- (for other build tools), e.g.:
- env PATH=/usr/sfw/bin:/usr/ccs/bin:$PATH sh -c './configure; make'
-
- (The only thing this misses is /usr/X11/lib/libXrandr.so.2, which is
- for the little used -xrandr option, see the script below to pick it up
- as well.)
-
-
- libjpeg is included in Solaris 9 and later (/usr/sfw/include and
- /usr/sfw/lib), and zlib in Solaris 8 and later (/usr/include and
- /usr/lib.) So on Solaris 9 you can pick up everything with something
- like this:
- env PATH=/usr/local/bin:/usr/ccs/bin:$PATH sh -c './configure --with-jpeg=/us
-r/sfw; make'
-
- assuming your gcc is in /usr/local/bin and x11vnc 0.7.1 or later.
- These are getting pretty long, see those assignments split up in the
- build script below.
-
-
- If your system does not have these libraries at all you can get the
- source for the libraries to build them: libjpeg is available at
- ftp://ftp.uu.net/graphics/jpeg/ and zlib at http://www.gzip.org/zlib/.
- See also http://www.sunfreeware.com/ for Solaris binary packages of
- these libraries as well as for gcc. Normally they will install into
- /usr/local but you can install them anywhere with the
- --prefix=/path/to/anywhere, etc.
-
-
- Here is a build script that indicates one way to pass the library
- locations information to the libvncserver configuration via the
- CPPFLAGS and LDFLAGS environment variables.
----8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8
-<---
-#!/bin/sh
-
-# Build script for Solaris, etc, with gcc, libjpeg and libz in
-# non-standard locations.
-
-# set to get your gcc, etc:
-#
-PATH=/path/to/gcc/bin:/usr/ccs/bin:/usr/sfw/bin:$PATH
-
-JPEG=/path/to/jpeg # set to maybe "/usr/local", "/usr/sfw", or "/opt/sfw"
-ZLIB=/path/to/zlib # set to maybe "/usr/local", "/usr/sfw", or "/opt/sfw"
-
-# Below we assume headers in $JPEG/include and $ZLIB/include and the
-# shared libraries are in $JPEG/lib and $ZLIB/lib. If your situation
-# is different change the locations in the two lines below.
-#
-CPPFLAGS="-I $JPEG/include -I $ZLIB/include"
-LDFLAGS="-L$JPEG/lib -R $JPEG/lib -L$ZLIB/lib -R $ZLIB/lib"
-
-# These two lines may not be needed on more recent Solaris releases:
-#
-CPPFLAGS="$CPPFLAGS -I /usr/openwin/include"
-LDFLAGS="$LDFLAGS -L/usr/openwin/lib -R /usr/openwin/lib"
-
-# These are for libXrandr.so on Solaris 10:
-#
-CPPFLAGS="$CPPFLAGS -I /usr/X11/include"
-LDFLAGS="$LDFLAGS -L/usr/X11/lib -R /usr/X11/lib"
-
-# Everything needs to built with _REENTRANT for thread safe errno:
-#
-CPPFLAGS="$CPPFLAGS -D_REENTRANT"
-
-export PATH CPPFLAGS LDFLAGS
-
-./configure
-make
-
-ls -l ./x11vnc/x11vnc
-
----8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8<---8
-<---
-
- Then do make install or copy the x11vnc binary to your desired
- destination.
-
- BTW, To run a shell script, just cut-and-paste the above into a file,
- say "myscript", then modify the "/path/to/..." items to correspond to
- your system/environment, and then type: "sh myscript" to run it.
-
- Note that on Solaris make is /usr/ccs/bin/make, so that is why the
- above puts /usr/ccs/bin in PATH. Other important build utilities are
- there too: ld, ar, etc. Also, it is probably a bad idea to have
- /usr/ucb in your PATH while building.
-
- Starting with the 0.7.1 x11vnc release the "configure --with-jpeg=DIR
- --with-zlib=DIR" options are handy if you want to avoid making a
- script.
-
- If you need to link OpenSSL libssl.a on Solaris see this method.
-
- If you need to build on Solaris 2.5.1 or earlier or other older Unix
- OS's, see this workaround FAQ.
-
-
- Building on FreeBSD, OpenBSD, ...: The jpeg libraries seem to be in
- /usr/local or /usr/pkg on these OS's. You won't need the openwin stuff
- in the above script (but you may need /usr/X11R6/....) Also starting
- with the 0.7.1 x11vnc release, this usually works:
- ./configure --with-jpeg=/usr/local
- make
-
-
- Building on HP-UX: For jpeg and zlib you will need to do the same
- sort of thing as described above for Solaris. You set CPPFLAGS and
- LDFLAGS to find them (see below for an example.) You do not need to do
- any of the above /usr/openwin stuff. Also, HP-UX does not seem to
- support -R, so get rid of the -R items in LDFLAGS. Because of this, at
- runtime you may need to set LD_LIBRARY_PATH or SHLIB_PATH to indicate
- the directory paths so the libraries can be found. It is a good idea
- to have static archives, e.g. libz.a and libjpeg.a for the nonstandard
- libraries so that they get bolted into the x11vnc binary (and so won't
- get "lost".)
-
- Here is what we recently did to build x11vnc 0.7.2 on HP-UX 11.11
-./configure --with-jpeg=$HOME/hpux/jpeg --with-zlib=$HOME/hpux/zlib
-make
-
- Where we had static archives (libjpeg.a, libz.a) only and header files
- in the $HOME/hpux/... directories as discussed for the build script.
-
- On HP-UX 11.23 and 11.31 we have had problems compiling with gcc.
- "/usr/include/rpc/auth.h:87: error: field 'syncaddr' has incomplete
- type". As a workaround for x11vnc 0.9.4 and later set your CPPFLAGS to
- include:
- CPPFLAGS="-DIGNORE_GETSPNAM"
- export CPPFLAGS
-
- This disables a very rare usage mode for -unixpw_nis by not trying
- getspnam(3).
-
- Using HP-UX's C compiler on 11.23 and 11.31 we have some severe
- compiler errors that have not been worked around yet. If you need to
- do this, contact me and I will give you a drastic recipe that will
- produce a working binary.
-
-
- Building on AIX: AIX: one user had to add the "X11.adt" package to
- AIX 4.3.3 and 5.2 to get build header files like XShm.h, etc. You may
- also want to make sure that /usr/lpp/X11/include, etc is being picked
- up by the configure and make.
-
- For a recent build on AIX 5.3 we needed to add these CFLAGS to be able
- to build with gcc:
- env CFLAGS='-maix64 -Xlinker -bbigtoc' ./configure ...
-
- we also built our own libjpeg and libz using -maix64.
-
- BTW, one way to run an Xvfb-like virtual X server for testing on AIX
- is something like "/usr/bin/X11/X -force -vfb -ac :1".
-
-
- Building on Mac OS X: There is now native Mac OS X support for
- x11vnc by using the raw framebuffer feature. This mode does not use or
- need X11 at all. To build you may need to disable X11:
-./configure --without-x ...
-make
-
- However, if your system has the Mac OS X build package for X11 apps
- you will not need to supply the "--without-x" option (in this case the
- resulting x11vnc would be able to export both the native Mac OS X
- display and windows displayed in the XDarwin X server.) Be sure to
- include the ./configure option to find libjpeg on your system.
-
-
- OpenSSL: Starting with version 0.8.3 x11vnc can now be built with
- SSL/TLS support. For this to be enabled the libssl.so library needs to
- be available at build time. So you may need to have additional
- CPPFLAGS and LDFLAGS items if your libssl.so is in a non-standard
- place. As of x11vnc 0.9.4 there is also the --with-ssl=DIR configure
- option.
-
- On Solaris using static archives libssl.a and libcrypto.a instead of
- .so shared libraries (e.g. from www.sunfreeware.com), we found we
- needed to also set LDFLAGS as follows to get the configure to work:
-env LDFLAGS='-lsocket -ldl' ./configure --with-ssl=/path/to/openssl ...
-make
-
- _________________________________________________________________
-
- Beta Testing:
-
- I don't have any formal beta-testers for the releases of x11vnc, so
- I'd appreciate any additional testing very much.
-
- Thanks to those who suggested features and helped beta test x11vnc
- 0.9.12 released in Sep 2010!
-
- Please help test and debug the 0.9.13 version for release sometime in
- Winter 2010.
-
- The version 0.9.13 beta tarball is kept here:
- x11vnc-0.9.13-dev.tar.gz
-
- There are also some Linux, Solaris, Mac OS X, and other OS test
- binaries here. Please kick the tires and report bugs, performance
- regressions, undesired behavior, etc. to me.
-
- To aid testing of the built-in SSL/TLS support for x11vnc, a number of
- VNC Viewer packages for Unix, Mac OS X, and Windows have been created
- that provide SSL Support for the TightVNC Viewer (this is done by
- wrapper scripts and a GUI that starts STUNNEL.) It should be pretty
- convenient for automatic SSL and SSH connections. It is described in
- detail at and can be downloaded from the Enhanced TightVNC Viewer
- (SSVNC) page. The SSVNC Unix viewer also supports x11vnc's symmetric
- key encryption ciphers (see the 'UltraVNC DSM Encryption Plugin'
- settings panel.)
-
-
- Here are some features that will appear in the 0.9.13 release:
- * Improved support for non-X11 touchscreen devices (e.g. handheld or
- cell phone) via Linux uinput input injection. Additional tuning
- parameters are added. TSLIB touchscreen calibration is supported.
- Tested on Qtmoko Neo Freerunner. A tool, misc/uinput.pl, is
- provided to diagnose uinput behavior on new devices. The env.
- vars. X11VNC_UINPUT_BUS and X11VNC_UINPUT_VERSION are available if
- leaving them unset does not work.
- * The Linux uinput non-X11 input injection can now be bypassed:
- events can be directly written to the /dev/input/event devices
- specified by the user (direct_abs=..., etc.) A -pipeinput input
- injection helper script, misc/qt_tslib_inject.pl is provided as a
- tweakable non-builtin direct input injection method.
- * The list of new uinput parameters for the above two features is:
- pressure, tslib_cal, touch_always, dragskip, btn_touch;
- direct_rel, direct_abs, direct_btn, direct_key.
- * The MacOSX native server can now use OpenGL for the screen
- capture. In nearly all cases this is faster than the raw
- framebuffer capture method. There are build and run time flags,
- X11VNC_MACOSX_NO_DEPRECATED, etc. to disable use of deprecated
- input injection and screen access interfaces. Cursor shape now
- works for 64bit binaries.
- * The included SSL enabled Java VNC Viewers now handle Mouse Wheel
- events.
- * miscellaneous new features and changes:
- * In -reflect mode, the libvncclient connection can now have the
- pixel format modified via the environment variables
- X11VNC_REFLECT_bitsPerSample, X11VNC_REFLECT_samplesPerPixel, and
- X11VNC_REFLECT_bytesPerPixel
- * In -create mode the following environment variables are added to
- fine tune the behavior: FIND_DISPLAY_NO_LSOF: do not use lsof(1)
- to try to determine the Linux VT, FIND_DISPLAY_NO_VT_FIND: do not
- try to determine the Linux VT at all, X11VNC_CREATE_LC_ALL_C_OK:
- do not bother undoing the setting LC_ALL=C that the create_display
- script sets. The performance of the -create script has been
- improved for large installations (100's of user sessions on one
- machine.)
- * In -unixpw mode, one can now Tab from login: to Password.
- * An environment variable, X11VNC_SB_FACTOR, allows one to scale the
- -sb screenblank sleep time from the default 2 secs.
- * An experimental option -unixsock is available for testing. Note,
- however, that it requires a manual change to
- libvncserver/rfbserver.c for it to work.
- * Documented that -grabkbd is no longer working with some/most
- window managers (it can prevent resizing and menu posting.)
-
-
- Here are some features that appeared in the 0.9.12 release (Sep/2010):
- * One can now specify the maximum number of displays that can be
- created in -create mode via the env. var.
- X11VNC_CREATE_MAX_DISPLAYS
- * The X11VNC_NO_LIMIT_SHM env. var. is added to skip any automatic
- shared memory reduction.
- * The kdm display manager is now detected when trying not to get
- killed by the display manager.
- * A compile time bug is fixed so that configuring using
- --with-system-libvncserver pointing to LibVNCServer 0.9.7 works
- again. A bug from forced use of Xdefs.h is worked around.
-
-
- Here are some features that appeared in the 0.9.11 release (Aug/2010):
- * The source tree is synchronized with the most recent libvncclient
- (this only affects -reflect mode.) Build is fixed for
- incompatibilities when using an external LibVNCServer (e.g.
- ./configure --with-system-libvncserver...) Please help test these
- build and runtime aspects and report back what you find, thanks.
- * The SSL enabled Java VNC Viewer Makefile has been modified so that
- the jar files that are built are compatible back to Java 1.4.
- * In -create/-unixpw mode, the env. var. FD_USERPREFS may be set to
- a filename in the user's home directory that includes default
- username:options values (so the options do not need to be typed
- every time at the login prompt.)
- * In -reflect mode cursor position updates are now handled
- correctly.
-
-
- Here are some features that appeared in the 0.9.10 release (May/2010):
- * The included SSL enabled Java applet viewer now supports Chained
- SSL Certificates. The debugCerts=yes applet parameter aids
- troubleshooting certificate validation. The x11vnc -ssl mode has
- always supported chained SSL certificates (simply put the
- intermediate certificates, in order, after the server certificate
- in the pem file.)
- * A demo CGI script desktop.cgi shows how to create an SSL
- encrypted, multi-user x11vnc web login desktop service. The script
- requires x11vnc version 0.9.10. The user logs into a secure web
- site and gets his/her own virtual desktop (Xvfb.) x11vnc's SSL
- enabled Java Viewer Applet is launched by the web browser for
- secure viewing (and so no software needs to be installed on the
- viewer-side.) One can use the desktop.cgi script for ideas to
- create their own fancier or customized web login desktop service
- (e.g. user-creation, PHP, SQL, specialized desktop application,
- etc.) More info here. There is also an optional 'port redirection'
- mode that allows redirection to other SSL enabled VNC servers
- running inside the firewall.
- * Built-in support for IPv6 (128 bit internet addresses) is now
- provided. See the -6 and -connect options for details.
- Additionally, in case there are still problems with built-in IPv6
- support, a transitional tool is provided in inet6to4 that allows
- x11vnc (or any other IPv4 application) to receive connections over
- IPv6.
- * The Xdummy wrapper script for Xorg's dummy driver is updated and
- no longer requires being run as root. New service options are
- provided to select Xdummy over Xvfb as the virtual X server to be
- created.
- * The "%" unix password verification tricks for the -unixpw option
- are now documented. They have also been extended to run a command
- as the user if one sets the environment variable UNIXPW_CMD. The
- desktop.cgi demo script takes advantage of this new feature.
- * A bug has been fixed that would prevent the Java applet viewer
- from being downloaded successfully in single-port HTTPS/VNC inetd
- mode. The env. var. X11VNC_HTTPS_DOWNLOAD_WAIT_TIME can be used to
- adjust for how many seconds a -inetd or -https httpd download is
- waited for (default 15 seconds.) The applet will now autodetect
- x11vnc and use GET=1 for faster connecting. Many other
- improvements and fixes.
- * The TightVNC security type (TightVNC features enabler) now works
- for RFB version 3.8.
- * The X property X11VNC_TRAP_XRANDR can be set on a desktop to force
- x11vnc to use the -xrandr screen size change trapping code.
- * New remote control query options: pointer_x, pointer_y,
- pointer_same, pointer_root, and pointer_mask. A demo script using
- them misc/panner.pl is provided.
- * The -sslScripts option prints out the SSL certificate management
- scripts.
-
-
- Here are some features that appeared in the 0.9.9 release (Dec/2009):
- * The -unixpw_system_greeter option, when used in combined unixpw
- and XDMCP FINDCREATEDISPLAY mode (for example: -xdmsvc), enables
- the user to press Escape to jump directly to the XDM/GDM/KDM login
- greeter screen. This way the user avoids entering his unix
- password twice at X session creation time. Also, the unixpw login
- panel now has a short help displayed if the user presses 'F1'.
- * x11vnc now tries to be a little bit more aggressive in keeping up
- with VNC client's framebuffer update requests. Some broken VNC
- clients like Eggplant and JollysFastVNC continuously spray these
- requests at VNC servers (regardless of whether they have received
- any updates or not.) Under some circumstances this could lead to
- x11vnc falling behind. The -extra_fbur option allows one to fine
- tune the setting. Additionally, one may also dial down delays:
- e.g. "-defer 5" and "-wait 5" (or to 1 or even 0) or -nonap or
- -allinput to keep up with these VNC clients at the expense of
- increased system load.
- * Heuristics are applied to try to determine if the X display is
- currently in a Display Manager Greeter Login panel (e.g. GDM) If
- so, x11vnc's creation of any windows and use of XFIXES are
- delayed. This is to try to avoid x11vnc being killed after the
- user logs in if the GDM KillInitClients=true is in effect. So one
- does not need to set KillInitClients=false. Note that in recent
- GDM the KillInitClients option has been removed. Also delayed is
- the use of the XFIXES cursor fetching functionality; this avoids
- an Xorg bug that causes Xorg to crash right after the user logs
- in.
- * A new option -findauth runs the FINDDISPLAY script that applies
- heuristics that try to determine the XAUTHORITY file. The use of
- '-auth guess' will use the XAUTHORITY that -findauth reveals. This
- can be handy in with the lastest GDM where the ability to store
- cookies in ~/.Xauthority has been removed. If x11vnc is running as
- root (e.g. inetd) and you add -env FD_XDM=1 to the above -findauth
- or -auth guess command lines, it will find the correct XAUTHORITY
- for the given display (this works for XDM/GDM/KDM if the login
- greeter panel is up or if someone has already logged into an X
- session.)
- * The FINDDISPLAY and FINDCREATEDISPLAY modes (i.e. "-display
- WAIT:cmd=...", -find, -create) now work correctly for the
- user-supplied login program scheme "-unixpw_cmd ...", as long as
- the login program supports running commands specified in the
- environment variable "RFB_UNIXPW_CMD_RUN" as the logged-in user.
- The mode "-unixpw_nis ..." has also been made more consistent.
- * The -stunnel option (like -ssl but uses stunnel as an external
- helper program) now works with the -ssl "SAVE" and "TMP" special
- certificate names. The -sslverify and -sslCRL options now work
- correctly in -stunnel mode. Single port HTTPS connections are also
- supported for this mode.
- * There is an experimental Application Sharing mode that improves
- upon the -id/-sid single window sharing: -appshare (run "x11vnc
- -appshare -help" for more info.) It is still very primitive and
- approximate, but at least it displays multiple top-level windows.
- * The remote control command -R can be used to instruct x11vnc to
- resend its most recent copy of the Clipboard, Primary, or
- Cutbuffer selections: "x11vnc -R resend_clipboard", "x11vnc -R
- resend_primary", and "x11vnc -R resend_cutbuffer".
- * The fonts in the GUI (-gui) can now by set via environment
- variables, e.g. -env X11VNC_FONT_BOLD='Helvetica -16 bold' and
- -env X11VNC_FONT_FIXED='Courier -14'.
- * The XDAMAGE mechanism is now automatically disabled for a period
- of time if a game or screensaver generates too many XDAMAGE
- rectangles per second. This avoids the X11 event queue from
- soaking up too much memory.
- * There is an experimental workaround: "-env X11VNC_WATCH_DX_DY=1"
- that tries to avoid problems with poorly constructed menu themes
- that place the initial position of the mouse cursor inside a menu
- item's active zone. More information can be found here.
-
-
- Here are some features that appeared in the 0.9.8 release (Jul/2009):
- * Stability improvements to -threads mode. Running x11vnc this way
- is more reliable now. Threaded operation sometimes gives better
- interactive response and faster updates: try it out. The threaded
- mode now supports multiple VNC viewers using the same VNC
- encoding. The threaded mode can also yield a performance
- enhancement in the many client case (e.g. class-room broadcast.)
- We have tested with 30 to 50 simultaneous clients. See also
- -reflect.
- For simultaneous clients: the ZRLE encoding is thread safe on all
- platforms, and the Tight and Zlib encodings are currently only
- thread safe on Linux where thread local storage, __thread, is
- used. If your non-Linux system and compiler support __thread one
- can supply -DTLS=__thread to enable it. When there is only one
- connected client, all encodings are safe on all platforms. Note
- that some features (e.g. scroll detection and -ncache) may be
- disabled or run with reduced functionality in -threads mode.
- * Automatically tries to work around an Xorg server and GNOME bug
- involving infinitely repeating keys when turning off key
- repeating. Use -repeat if the automatic workaround fails.
- * Improved reliability of the Single Port SSL VNC and HTTPS java
- viewer applet delivery mechanism.
- * The -clip mode works under -rawfb.
-
-
- Here are some features that appeared in the 0.9.7 release (Mar/2009):
- * Support for polling Linux Virtual Terminals (also called virtual
- consoles) directly instead of using /dev/fb. The option to use is,
- for example, "-rawfb vt2" for Virtual Terminal 2, etc. In this
- case the special file /dev/vcsa2 is used to retrieve vt2's current
- text. Text and colors are shown, but no graphics.
- * Support for less than 8 bits per pixel framebuffers (e.g. 4 or 1
- bpp) in the -rawfb mode.
- * The SSL enabled UltraVNC Java viewer applet now has a [Home] entry
- in the "drives" drop down menu. This menu can be configured with
- the ftpDropDown applet parameter. All of the applet parameters are
- documented in classes/ssl/README.
- * Experimental support for VirtualGL's TurboVNC (an enhanced
- TightVNC for fast LAN high framerate usage.)
- * The CUPS Terminal Services helper mode has been improved.
- * Improvements to the -ncache_cr that allows smooth opaque window
- motions using the 'copyrect' encoding when using -ncache mode.
- * The -rmflag option enables a way to indicate to other processes
- x11vnc has exited.
- * Reverse connections using anonymous Diffie Hellman SSL encryption
- now work.
-
-
- Here are some features that appeared in the 0.9.6 release (Dec/2008):
- * Support for VeNCrypt SSL/TLS encrypted connections. It is enabled
- by default in the -ssl mode. VNC Viewers like vinagre,
- gvncviewer/gtk-vnc, the vencrypt package, SSVNC, and others
- support this encryption mode. It can also be used with the -unixpw
- option to enable Unix username and password authentication
- (VeNCrypt's "*Plain" modes.) A similar but older VNC security type
- "ANONTLS" (used by vino) is supported as well. See the -vencrypt
- and -anontls options for additional control. The difference
- between x11vnc's normal -ssl mode and VeNCrypt is that the former
- wraps the entire VNC connection in SSL (like HTTPS does for HTTP,
- i.e. "vncs://") while VeNCrypt switches on the SSL/TLS at a
- certain point during the VNC handshake. Use -sslonly to disable
- both VeNCrypt and ANONTLS (vino.)
- * The "-ssl ANON" option enables Anonymous Diffie-Hellman (ADH) key
- exchange for x11vnc's normal SSL/TLS operation. Note that
- Anonymous Diffie-Hellman uses encryption for privacy, but provides
- no authentication and so is susceptible to Man-In-The-Middle
- attacks (and so we do not recommend it: we prefer you use "-ssl
- SAVE", etc. and have the VNC viewer verify the cert.) The ANONTLS
- mode (vino) only supports ADH. VeNCrypt mode supports both ADH and
- regular X509 SSL certificates modes. For these ADH is enabled by
- default. See -vencrypt and -anontls for how to disable ADH.
- * For x11vnc's SSL/TLS modes, one can now specify a Certificate
- Revocation List (CRL) with the -sslCRL option. This will only be
- useful for wide deployments: say a company-wide x11vnc SSL access
- deployment using a central Certificate Authority (CA) via
- -sslGenCA and -sslGenCert. This way if a user has his laptop lost
- or stolen, you only have to revoke his key instead of creating a
- new Certificate Authority and redeploying new keys to all users.
- * The default SSL/TLS mode, "-ssl" (no pem file parameter supplied),
- is now the same as "-ssl SAVE" and will save the generated
- self-signed cert in "~/.vnc/certs/server.pem". Previously "-ssl"
- would create a temporary self-signed cert that was discarded when
- x11vnc exited. The reason for the change is to at least give the
- chance for the VNC Viewer side (e.g. SSVNC) to remember the cert
- to authenticate subsequent connections to the same x11vnc server.
- Use "-ssl TMP" to regain the previous behavior. Use "-ssl
- SAVE_NOPROMPT" to avoid being prompted about using passphrase when
- the certificate is created.
- * The option -http_oneport enables single-port HTTP connections via
- the Java VNC Viewer. So, for example, the web browser URL
- "http://myhost.org:5900" works the same as
- "http://myhost.org:5800", but with the convenience of only
- involving one port instead of two. This works for both unencrypted
- connections and for SSH tunnels (see -httpsredir if the tunnel
- port differs.) Note that HTTPS single-port operation in -ssl SSL
- encrypted mode has been available since x11vnc version 0.8.3.
- * For the -avahi/-zeroconf Service Advertizing mode, if x11vnc was
- not compiled with the avahi-client library, then an external
- helper program, either avahi-publish(1) (on Unix) or dns-sd(1) (on
- Mac OS X), is used instead.
- * The "-rfbport PROMPT" option will prompt the user via the GUI to
- select the VNC port (e.g. 5901) to listen on, and a few other
- basic settings. This enables a handy GUI mode for naive users:
- x11vnc -gui tray=setpass -rfbport PROMPT -logfile $HOME/.x11vnc.log.%VNCDISP
-LAY
- suitable for putting in a launcher or menu, e.g. x11vnc.desktop.
- The -logfile expansion is new too. In the GUI, the tray=setpass
- Properties panel has been improved.
- * The -solid solid background color option now works for the Mac OS
- X console.
- * The -reopen option instructs x11vnc to try to reopen the X display
- if it is prematurely closed by, say, the display manager (e.g.
- GDM.)
-
-
- Here are some features that appeared in the 0.9.5 release (Oct/2008):
- * Symmetric key encryption ciphers. ARC4, AES-128, AES-256,
- blowfish, and 3des are supported. Salt and initialization vector
- seeding is provided. These compliment the more widely used SSL and
- SSH encryption access methods. SSVNC also supports these
- encryption modes.
- * Scaling differently along the X- and Y-directions. E.g. "-scale
- 1280x1024" or "-scale 0.8x0.75" Also, "-geometry WxH" is an
- alias for "-scale WxH"
- * By having SSVNC version 1.0.21 or later available in your $PATH,
- the -chatwindow option allows a UltraVNC Text Chat window to
- appear on the local X11 console/display (this way the remote
- viewer can chat with the person at the physical display; e.g.
- helpdesk mode.) This also works on the Mac OS X console if the
- Xquartz X11 server (enabled by default on leopard) is running for
- the chatwindow.
- * The HTTP Java viewer applet jar, classes/VncViewer.jar, has been
- updated with an improved implementation based on the code used by
- the classes/ssl applets.
-
-
- Here are some features that appeared in the 0.9.4 release (Sep/2008):
- * Improvements to the -find and -create X session finding or
- creating modes: new desktop types and service redirection options.
- Personal cupsd daemon and SSH port redirection helper for use with
- SSVNC's Terminal Services feature.
- * Reverse VNC connections via -connect work in the -find, -create
- and related -display WAIT:... modes.
- * Reverse VNC connections (either normal or SSL) can use a Web Proxy
- or a SOCKS proxy, or a SSH connection, or even a CGI URL to make
- the outgoing connection. See: -proxy. Forward connections can also
- use: -ssh.
- * Reverse VNC connections via the UltraVNC repeater proxy (either
- normal or SSL) are supported. Use either the "-connect
- repeater=ID:NNNN+host:port" or "-connect
- repeater://host:port+ID:NNNN" notation. The SSVNC VNC viewer also
- supports the UltraVNC repeater. Also, a perl repeater implemention
- is here: ultravnc_repeater.pl
- * Support for indexed colormaps (PseudoColor) with depths other than
- 8 (from 1 to 16 now work) for non-standard hardware. Option
- "-advertise_truecolor" to handle some workaround in this mode.
- * Support for the ZYWRLE encoding, this is the RealVNC ZRLE encoding
- extended to do motion video and photo regions more efficiently by
- way of a Wavelet based transformation.
- * The -finddpy and -listdpy utilities help to debug and configure
- the -find, -create, and -display WAIT:... modes.
- * Some automatic detection of screen resizes are handled even if the
- -xrandr option is not supplied.
- * The -autoport options gives more control over the VNC port x11vnc
- chooses.
- * The -ping secs can be used to help keep idle connections alive.
- * Pasting of the selection/clipboard into remote applications (e.g.
- Java) has been improved.
- * Fixed a bug if a client disconnects during the 'speed-estimation'
- phase.
- * To unset Caps_Lock, Num_Lock and raise all keys in the X server
- use -clear_all.
- * Usage with dvorak keyboards has been improved. See also: -xkb.
- * The Java Viewer applet source code is now included in the
- x11vnc-0.9.*.tar.gz tarball. This means you can now build the Java
- viewer applet jar files from source. If you stopped shipping the
- Java viewer applet jar files due to lack of source code, you can
- start again.
-
-
- Here are some features that appeared in the 0.9.3 release (Oct/2007):
- * Viewer-side pixmap caching. A large area of pixels (at least 2-3
- times as big as the framebuffer itself; the bigger the better...
- default is 10X) is placed below the framebuffer to act as a
- buffer/cache area for pixel data. The VNC CopyRect encoding is
- used to move it around, so any viewer can take advantage of it.
- Until we start modifying viewers you will be able to see the cache
- area if you scroll down (this makes it easier to debug!) For
- testing the default is "-ncache 10". The unix Enhanced TightVNC
- Viewer ssvnc has a nice -ycrop option to help hide the pixel cache
- area from view.
-
-
- Here are some features that appeared in the 0.9.2 release (Jun/2007):
- * Building with no OpenSSL libssl available (or with --without-ssl)
- has been fixed.
- * One can configure x11vnc via "./configure
- --with-system-libvncserver" to use a system installed libvncserver
- library instead of the one bundled in the release tarball.
- * If UltraVNC file transfer or chat is detected, then VNC clients
- are "pinged" more often to prevent these side channels from
- becoming serviced too infrequently.
- * In -unixpw mode in the username and password dialog no text will
- be echoed if the first character sent is "Escape". This enables a
- convenience feature in SSVNC to send the username and password
- automatically.
-
-
- Here are some features that appeared in the 0.9.1 release (May/2007):
- * The UltraVNC Java viewer has been enhanced to support SSL (as the
- TightVNC viewer had been previously.) The UltraVNC Java supports
- ultravnc filetransfer, and so can be used as a VNC viewer on Unix
- that supports ultravnc filetransfer. It is in the
- classes/ssl/UltraViewerSSL.jar file (that is pointed to by
- ultra.vnc.) The signed applet SignedUltraViewerSSL.jar version
- (pointed to by ultrasigned.vnc) will be needed to access the local
- drive if you are using it for file transfer via a Web browser.
- Some other bugs in the UltraVNC Java viewer were fixed and a few
- improvements to the UI made.
- * A new Unix username login mode for VNC Viewers authenticated via a
- Client SSL Certificate: "-users sslpeer=". The emailAddress
- subject field is inspected for username@hostname and then acts as
- though "-users +username" has been supplied. This way the Unix
- username is identified by (i.e. simply extracted from) the Client
- SSL Certificate. This could be useful with -find, -create and -svc
- modes if you are also have set up and use VNC Client SSL
- Certificate authentication.
- * For external display finding/creating programs (e.g. WAIT:cmd=...)
- if the VNC Viewer is authenticated via a Client SSL Certificate,
- then that Certificate is available in the environment variable
- RFB_SSL_CLIENT_CERT.
-
-
- Here are some features that appeared in the 0.9 release (Apr/2007):
- * VNC Service advertising via mDNS / ZeroConf / BonJour with the
- Avahi client library. Enable via "-avahi" or "-zeroconf".
- * Implementations of UltraVNC's TextChat, SingleWindow, and
- ServerInput extensions (requires ultravnc viewer or ssvnc Unix
- viewer.) They toggle the selection of a single window (-id), and
- disable (friendly) user input and viewing (monitor blank) at the
- VNC server.
- * Short aliases "-find", "-create", "-svc", and "-xdmsvc" for
- commonly used FINDCREATEDISPLAY usage modes.
- * Reverse VNC connections (viewer listening) now work in SSL (-ssl)
- mode.
- * New options to control the Monitor power state and keyboard/mouse
- grabbing: -forcedpms, -clientdpms, -noserverdpms, and -grabalways.
- * A simple way to emulate inetd(8) to some degree via the "-loopbg"
- option.
- * Monitor the accuracy of XDAMAGE and apply "-noxdamage" if it is
- not working well. OpenGL applications like like beryl and MythTv
- have been shown to make XDAMAGE not work properly.
- * For Java SSL connections involving a router/firewall port
- redirection, an option -httpsredir to spare the user from needing
- to include &PORT=NNN in the browser URL.
-
-
- Here are some features that appeared in the 0.8.4 release (Feb/2007):
- * Native Mac OS X Aqua/Quartz support. (i.e. OSXvnc alternative;
- some activities are faster)
- * A new login mode: "-display WAIT:cmd=FINDCREATEDISPLAY -unixpw
- ..." that will Create a new X session (either virtual or real and
- with or without a display manager, e.g. kdm) for the user if it
- cannot find the user's X session display via the FINDDISPLAY
- method. See the -svc and the -xdmsvc aliases.
- * x11vnc can act as a VNC reflector/repeater using the "-reflect
- host:N" option. Instead of polling an X display, the remote VNC
- Server host:N is connected to and re-exported via VNC. This is
- intended for use in broadcasting a display to many (e.g. > 16;
- classroom or large demo) VNC viewers where bandwidth and other
- resources are conserved by spreading the load over a number of
- repeaters.
- * Wireframe copyrect detection for local user activity (e.g. someone
- sitting at the physical display moving windows) Use
- -nowireframelocal to disable.
- * The "-N" option couples the VNC Display number to the X Display
- number. E.g. if your X DISPLAY is :2 then the VNC display will be
- :2 (i.e. using port 5902.) If that port is taken x11vnc will exit.
- * Option -nodpms to avoid problems with programs like KDE's
- kdesktop_lock that keep restarting the screen saver every few
- seconds.
- * To automatically fix the common mouse motion problem on XINERAMA
- (multi-headed) displays, the -xwarppointer option is enabled by
- default when XINERAMA is active.
-
- If you have a Mac please try out the native Mac OS X support, build
- with "./configure --without-x", or download a binary mentioned above,
- (even if you don't plan on ever using it in this mode!), and let me
- know how it went. Thanks.
-
-
- Here are some features that appeared in the 0.8.3 release (Nov/2006):
- * The -ssl option provides SSL encryption and authentication
- natively via the www.openssl.org library. One can use from a
- simple self-signed certificate server certificate up to full CA
- and client certificate authentication schemes.
- * Similar to -ssl, the -stunnel option starts up a SSL tunnel server
- stunnel (that must be installed separately on the system:
- stunnel.mirt.net ) to allow only encrypted SSL connections from
- the network.
- * The -sslverify option allows for authenticating VNC clients via
- their certificates in either -ssl or -stunnel modes.
- * Certificate creation and management tools are provide in the
- -sslGenCert, -sslGenCA, and related options.
- * An SSL enabled Java applet VNC Viewer applet is provided by x11vnc
- in classes/ssl/VncViewer.jar. In addition to normal HTTP, the
- applet may be loaded into the web browser via HTTPS (HTTP over
- SSL.) (one can use the VNC port, e.g. https://host:5900/, or also
- the separate -https port option.) A wrapper shell script
- ss_vncviewer is also provided that sets up a stunnel client-side
- tunnel on Unix systems. See Enhanced TightVNC Viewer (SSVNC) for
- other SSL/SSH viewer possibilities.
- * The -unixpw option supports Unix username and password
- authentication (a simpler variant is the -unixpw_nis option that
- works in environments where the encrypted passwords are readable,
- e.g. NIS.) The -ssl or -localhost + -stunnel options are enforced
- in this mode to prevent password sniffing. As a convenience, these
- requirements are lifted if a SSH tunnel can be deduced (but
- -localhost still applies.)
- * Coupling -unixpw with "-display WAIT:cmd=FINDDISPLAY" or "-display
- WAIT:cmd=FINDCREATEDISPLAY" provides a way to allow a user to
- login with their UNIX password and have their display connected to
- automatically. See the -svc and the -xdmsvc aliases.
- * Hooks are provided in the -unixpw_cmd and "-passwdfile
- cmd:,custom:..." options to allow you to supply your own
- authentication and password lookup programs.
- * x11vnc can be configured and built to not depend on X11 libraries
- "./configure --without-x" for -rawfb only operation (e.g. embedded
- linux console devices.)
- * The -rotate option enables you to rotate or reflect the screen
- before exporting via VNC. This is intended for use on handhelds
- and other devices where the rotation orientation is not "natural".
- * The "-ultrafilexfer" alias is provided and improved UltraVNC
- filetransfer rates have been achieved.
- * Under the "-connect_or_exit host" option x11vnc will exit
- immediately unless the reverse connection to host succeeds. The
- "-rfbport 0" option disables TCP listening for connections (useful
- for this mode.)
- * The "-rawfb rand" and "-rawfb none" options are useful for testing
- automation scripts, etc., without requiring a full desktop.
- * Reduced spewing of information at startup, use "-verbose" (also
- "-v") to turn it back on for debugging or if you are going to send
- me a problem report.
-
- Here are some Previous Release Notes
- _________________________________________________________________
-
- Some Notes:
-
- Both a client and a server: It is sometimes confusing to people that
- x11vnc is both a client and a server at the same time. It is an X
- client because it connects to the running X server to do the screen
- polls. Think of it as a rather efficient "screenshot" program running
- continuously. It is a server in the sense that it is a VNC server that
- VNC viewers on the network can connect to and view the screen
- framebuffer it manages.
-
- When trying to debug problems, remember to think of both roles. E.g.
- "how is x11vnc connecting to the X server?", "how is the vncviewer
- connecting to x11vnc?", "what permits/restricts the connection?". Both
- links may have reachability, permission, and other issues.
-
- Network performance: Whether you are using Xvnc or x11vnc it is
- always a good idea to have a solid background color instead of a
- pretty background image. Each and every re-exposure of the background
- must be resent over the network: better to have that background be a
- solid color that compresses very well compared to a photo image. (This
- is one place where the X protocol has an advantage over the VNC
- protocol.) I suggest using xsetroot, dtstyle or similar utility to set
- a solid background while using x11vnc. You can turn the pretty
- background image back on when you are using the display directly.
- Update: As of Feb/2005 x11vnc has the -solid [color] option that works
- on recent GNOME, KDE, and CDE and also on classic X (background image
- is on the root window.) Update: As of Oct/2007 x11vnc has the -ncache
- option that does a reasonable job caching the background (and other)
- pixmap data on the viewer side.
-
- I also find the TightVNC encoding gives the best response for my usage
- (Unix <-> Unix over cable modem.) One needs a tightvnc-aware vncviewer
- to take advantage of this encoding.
-
- TCP port issues: Notice the lines
- 18/07/2003 14:36:31 Autoprobing selected port 5900
- PORT=5900
-
- in the output. 5900 is the default VNC listening port (just like 6000
- is X11's default listening port.) Had port 5900 been taken by some
- other application, x11vnc would have next tried 5901. That would mean
- the viewer command above should be changed to vncviewer
- far-away.east:1. You can force the port with the "-rfbport NNNN"
- option where NNNN is the desired port number. If that port is already
- taken, x11vnc will exit immediately. The "-N" option will try to match
- the VNC display number to the X display. (also see the "SunRay
- Gotcha" note below)
-
- Options: x11vnc has (far too) many features that may be activated
- via its command line options. Useful options are, e.g., -scale to do
- server-side scaling, and -rfbauth passwd-file to use VNC password
- protection (the vncpasswd or storepasswd programs, or the x11vnc
- -storepasswd option can be used to create the password file.)
-
- Algorithm: How does x11vnc do it? Rather brute-forcedly: it
- continuously polls the X11 framebuffer for changes using
- XShmGetImage(). When changes are discovered, it instructs libvncserver
- which rectangular regions of the framebuffer have changed, and
- libvncserver compresses the changes and sends them off to any
- connected VNC viewers. A number of applications do similar things,
- such as x0rfbserver, krfb, x0vncserver, vino. x11vnc uses a 32 x 32
- pixel tile model (the desktop is decomposed into roughly 1000 such
- tiles), where changed tiles are found by pseudo-randomly polling 1
- pixel tall horizontal scanlines separated vertically by 32 pixels.
- This is a surprisingly effective algorithm for finding changed
- regions. For keyboard and mouse user input the XTEST extension is used
- to pass the input events to the X server. To detect XBell "beeps" the
- XKEYBOARD extension is used. If available, the XFIXES extension is
- used to retrieve the current mouse cursor shape. Also, if available
- the X DAMAGE extension is used to receive hints from the X server
- where modified regions on the screen are. This greatly reduces the
- system load when not much is changing on the screen and also improves
- how quickly the screen is updated.
-
- Barbershop mirrors effect: What if x11vnc is started up, and
- vncviewer is then started up on the same machine and displayed on the
- same display x11vnc is polling? One might "accidentally" do this when
- first testing out the programs. You get an interesting
- recursive/feedback effect where vncviewer images keep popping up each
- one contained in the previous one and slightly shifted a bit by the
- window manager decorations. There will be an even more interesting
- effect if -scale is used. Also, if the XKEYBOARD is supported and the
- XBell "beeps" once, you get an infinite loop of beeps going off.
- Although all of this is mildly exciting it is not much use: you will
- normally run and display the viewer on a different machine!
- _________________________________________________________________
-
- Sun Ray Notes:
-
- You can run x11vnc on your (connected or disconnected) SunRay session.
- Here are some notes on SunRay usage with x11vnc.
-
- _________________________________________________________________
-
- Limitations:
-
- * Due to the polling nature, some activities (opaque window moves,
- scrolling), can be pretty choppy/ragged and others (exposures of
- large areas) slow. Experiment with interacting a bit differently
- than you normally do to minimize the effects (e.g. do fullpage
- paging rather than line-by-line scrolling, and move windows in a
- single, quick motion.) Recent work has provided the
- -scrollcopyrect and -wireframe speedups using the CopyRect VNC
- encoding and other things, but they only speed up some activities,
- not all.
- * A rate limiting factor for x11vnc performance is that graphics
- hardware is optimized for writing, not reading (x11vnc reads the
- video framebuffer for the screen image data.) The difference can
- be a factor of 10 to 1000, and so it usually takes about 0.5-1 sec
- to read in the whole video hardware framebuffer (e.g. 5MB for
- 1280x1024 at depth 24 with a read rate of 5-10MB/sec.) So whenever
- activity changes most of the screen (e.g. moving or iconifying a
- large window) there is a delay of 0.5-1 sec while x11vnc reads the
- changed regions in.
- A slow framebuffer read rate will often be the performance
- bottleneck on a fast LAN (whereas on slower links the reduced
- network bandwidth becomes the bottleneck.)
- Note: A quick way to get a 2X speedup of this for x11vnc is to
- switch your X server from depth 24 (32bpp) to depth 16 (16bpp.)
- You get a 4X speedup going to 8bpp, but the lack of color cells is
- usually unacceptable.
- To get a sense of the read and write speeds of your video card,
- you can run benchmarks like: "x11perf -getimage500", "x11perf
- -putimage500", "x11perf -shmput500" and for XFree86 displays with
- direct graphics access the "dga" command (press "b" to run the
- benchmark and then after a few seconds press "q" to quit.) Even
- this "dd if=/dev/fb0 of=/dev/null" often gives a good estimate.
- x11vnc also prints out its estimate:
- 28/02/2009 11:11:07 Autoprobing TCP port
- 28/02/2009 11:11:07 Autoprobing selected port 5900
- 28/02/2009 11:11:08 fb read rate: 10 MB/sec
- 28/02/2009 11:11:08 screen setup finished.
- We have seen a few cases where the hardware fb read speed is
- greater than 65 MB/sec: on high end graphics workstations from SGI
- and Sun, and also from a Linux user using nvidia proprietary
- drivers for his nvidia video card. Update 2008: thankfully, these
- sped up drivers are becoming more common on Linux and *BSD systems
- and that makes x11vnc run somewhat more quickly. Sometimes they
- have a read rate of over 400 MB/sec.
- On XFree86/Xorg it is actually possible to increase the
- framebuffer read speed considerably (10-100 times) by using the
- Shadow Framebuffer (a copy of the framebuffer is kept in main
- memory and this can be read much more quickly.) To do this one
- puts the line Option "ShadowFB" "true" in the Device section of
- the /etc/X11/XF86Config or /etc/X11/xorg.conf file. Note that this
- disables 2D acceleration at the physical display and so that might
- be unacceptable if one plays games, etc. on the machine's local
- display. Nevertheless this could be handy in some circumstances,
- e.g. if the slower speed while sitting at the physical display was
- acceptable (this seems to be true for most video cards these
- days.) Unfortunately it does not seem shadowfb can be turned on
- and off dynamically...
- Another amusing thing one can do is use Xvfb as the X server, e.g.
- "xinit $HOME/.xinitrc -- /usr/X11R6/bin/Xvfb :1 -screen 0
- 1024x768x16" x11vnc can poll Xvfb efficiently via main memory.
- It's not exactly clear why one would want to do this instead of
- using vncserver/Xvnc, (perhaps to take advantage of an x11vnc
- feature, such as framebuffer scaling or built-in SSL encryption),
- but we mention it because it may be of use for special purpose
- applications. You may need to use the "-cc 4" option to force Xvfb
- to use a TrueColor visual instead of DirectColor. See also the
- description of the -create option that does all of this
- automatically for you (be sure to install the Xvfb package, e.g.
- apt-get install xvfb.)
- Also, a faster and more accurate way is to use the "dummy"
- Xorg/XFree86 device driver (or our Xdummy wrapper script.) See
- this FAQ for details.
- * Somewhat surprisingly, the X11 mouse (cursor) shape is write-only
- and cannot be queried from the X server. So traditionally in
- x11vnc the cursor shape stays fixed at an arrow. (see the "-cursor
- X" and "-cursor some" options, however, for a partial hack for the
- root window, etc.) However, on Solaris using the SUN_OVL overlay
- extension, x11vnc can show the correct mouse cursor when the
- -overlay option is also supplied. A similar thing is done on IRIX
- as well when -overlay is supplied.
- More generally, as of Dec/2004 x11vnc supports the new XFIXES
- extension (in Xorg and Solaris 10) to query the X server for the
- exact cursor shape, this works pretty well except that cursors
- with transparency (alpha channel) need to approximated to solid
- RGB values (some cursors look worse than others.)
- * Audio from applications is of course not redirected (separate
- redirectors do exist, e.g. esd, see the FAQ on this below.) The
- XBell() "beeps" will work if the X server supports the XKEYBOARD
- extension. (Note that on Solaris XKEYBOARD is disabled by default.
- Passing +kb to Xsun enables it.)
- * The scroll detection algorithm for the -scrollcopyrect option can
- give choppy or bunched up transient output and occasionally
- painting errors.
- * Using -threads can expose some bugs/crashes in libvncserver.
-
- Please feel free to contact me if you have any questions, problems, or
- comments about x11vnc, etc. Please be polite, thorough, and not
- demanding (sadly, the number of people contacting me that are rude and
- demanding is increasing dramatically.)
- Also, some people ask if they can make a donation, see this link for
- that.
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/faq.html:
-
-
- x11vnc Home Donations
- _________________________________________________________________
-
- x11vnc FAQ:
-
-
- [Building and Starting]
-
- Q-1: I can't get x11vnc to start up. It says "XOpenDisplay failed
- (null)" or "Xlib: connection to ":0.0" refused by server Xlib: No
- protocol specified" and then exits. What do I need to do?
-
- Q-2: I can't get x11vnc and/or libvncserver to compile.
-
- Q-3: I just built x11vnc successfully, but when I use it my keystrokes
- and mouse button clicks are ignored (I am able to move the mouse
- though.)
-
- Q-4: Help, I need to run x11vnc on Solaris 2.5.1 (or other old
- Unix/Linux) and it doesn't compile!
-
- Q-5: Where can I get a precompiled x11vnc binary for my Operating
- System?
-
- Q-6: Where can I get a VNC Viewer binary (or source code) for the
- Operating System I will be viewing from?
-
- Q-7: How can I see all of x11vnc's command line options and
- documentation on how to use them?
-
- Q-8: I don't like typing arcane command line options every time I
- start x11vnc. What can I do? Is there a config file? Or a GUI?
-
- Q-9: How can I get the GUI to run in the System Tray, or at least be a
- smaller, simpler icon?
-
- Q-10: How can I get x11vnc to listen on a different port besides the
- default VNC port (5900)?
-
- Q-11: My Firewall/Router doesn't allow VNC Viewers to connect to
- x11vnc.
-
- Q-12: Is it possible for a VNC Viewer and a VNC Server to connect to
- each other even though both are behind Firewalls that block all
- incoming connections?
-
- Q-13: Can I make x11vnc more quiet and also go into the background
- after starting up?
-
- Q-14: Sometimes when a VNC viewer dies abruptly, x11vnc also dies with
- the error message like: "Broken pipe". I'm using the -forever mode and
- I want x11vnc to keep running.
-
- Q-15: The Windows TightVNC 1.3.9 Viewer cannot connect to x11vnc.
-
- Q-16: KDE's krdc VNC viewer cannot connect to x11vnc.
-
- Q-17: When I start x11vnc on an Alpha Tru64 workstation the X server
- crashes!
-
- Q-18: When running x11vnc on an IBM AIX workstation after a few
- minutes the VNC connection freezes.
-
- Q-19: Are there any build-time customizations possible, e.g. change
- defaults, create a smaller binary, etc?
-
- [Win2VNC Related]
-
- Q-20: I have two separate machine displays in front of me, one Windows
- the other X11: can I use x11vnc in combination with Win2VNC in
- dual-screen mode to pass the keystrokes and mouse motions to the X11
- display?
-
- Q-21: I am running Win2VNC on my Windows machine and "x11vnc -nofb" on
- Unix to pass keyboard and mouse to the Unix monitor. Whenever I start
- Win2VNC it quickly disconnects and x11vnc says:
- rfbProcessClientNormalMessage: read: Connection reset by peer
-
- Q-22: Can I run "x11vnc -nofb" on a Mac OS X machine to redirect mouse
- and keyboard input to it from Windows and X11 machines via Win2VNC and
- x2vnc, respectively?
-
- [Color Issues]
-
- Q-23: The X display I run x11vnc on is only 8 bits per pixel (bpp)
- PseudoColor (i.e. only 256 distinct colors.) The x11vnc colors may
- start out OK, but after a while they are incorrect in certain windows.
-
- Q-24: Color problems: Why are the colors for some windows incorrect in
- x11vnc? BTW, my X display has nice overlay/multi-depth visuals of
- different color depths: e.g. there are both depth 8 and 24 visuals
- available at the same time.
-
- Q-25: I am on a high color system (depth >= 24) but I seem to have
- colormap problems. They either flash or everything is very dark.
-
- Q-26: How do I figure out the window id to supply to the -id windowid
- option?
-
- Q-27: Why don't menus or other transient windows come up when I am
- using the -id windowid option to view a single application window?
-
- Q-28: My X display is depth 24 at 24bpp (instead of the normal depth
- 24 at 32bpp.) I'm having lots of color and visual problems with x11vnc
- and/or vncviewer. What's up?
-
- [Xterminals]
-
- Q-29: Can I use x11vnc to view and interact with an Xterminal (e.g.
- NCD) that is not running UNIX and so x11vnc cannot be run on it
- directly?
-
- Q-30: How do I get my X permissions (MIT-MAGIC-COOKIE file) correct
- for a Unix/Linux machine acting as an Xterminal?
-
- [Sun Rays]
-
- Q-31: I'm having trouble using x11vnc with my Sun Ray session.
-
- [Remote Control]
-
- Q-32: How do I stop x11vnc once it is running in the background?
-
- Q-33: Can I change settings in x11vnc without having to restart it?
- Can I remote control it?
-
- [Security and Permissions]
-
- Q-34: How do I create a VNC password for use with x11vnc?
-
- Q-35: Can I make it so -storepasswd doesn't show my password on the
- screen?
-
- Q-36: Can I have two passwords for VNC viewers, one for full access
- and the other for view-only access to the display?
-
- Q-37: Can I have as many full-access and view-only passwords as I
- like?
-
- Q-38: Does x11vnc support Unix usernames and passwords? Can I further
- limit the set of Unix usernames who can connect to the VNC desktop?
-
- Q-39: Can I supply an external program to provide my own custom login
- method (e.g. Dynamic/One-time passwords or non-Unix (LDAP) usernames
- and passwords)?
-
- Q-40: Why does x11vnc exit as soon as the VNC viewer disconnects? And
- why doesn't it allow more than one VNC viewer to connect at the same
- time?
-
- Q-41: Can I limit which machines incoming VNC clients can connect
- from?
-
- Q-42: How do I build x11vnc/libvncserver with libwrap (tcp_wrappers)
- support?
-
- Q-43: Can I have x11vnc only listen on one network interface (e.g.
- internal LAN) rather than having it listen on all network interfaces
- and relying on -allow to filter unwanted connections out?
-
- Q-44: Now that -localhost implies listening only on the loopback
- interface, how I can occasionally allow in a non-localhost via the -R
- allowonce remote control command?
-
- Q-45: Can I fine tune what types of user input are allowed? E.g. have
- some users just be able to move the mouse, but not click or type
- anything?
-
- Q-46: Can I prompt the user at the local X display whether the
- incoming VNC client should be accepted or not? Can I decide to make
- some clients view-only? How about running an arbitrary program to make
- the decisions?
-
- Q-47: I start x11vnc as root because it is launched via inetd(8) or a
- display manager like gdm(1). Can I have x11vnc later switch to a
- different user?
-
- Q-48: I use a screen-lock when I leave my workstation (e.g.
- xscreensaver or xlock.) When I remotely access my workstation desktop
- via x11vnc I can unlock the desktop fine, but I am worried people will
- see my activities on the physical monitor. What can I do to prevent
- this, or at least make it more difficult?
-
- Q-49: Can I have x11vnc automatically lock the screen when I
- disconnect the VNC viewer?
-
- [Encrypted Connections]
-
- Q-50: How can I tunnel my connection to x11vnc via an encrypted SSH
- channel between two Unix machines?
-
- Q-51: How can I tunnel my connection to x11vnc via an encrypted SSH
- channel from Windows using an SSH client like Putty?
-
- Q-52: How can I tunnel my connection to x11vnc via an encrypted SSL
- channel using an external tool like stunnel?
-
- Q-53: Does x11vnc have built-in SSL tunneling?
-
- Q-54: How do I use VNC Viewers with built-in SSL tunneling?
-
- Q-55: How do I use the Java applet VNC Viewer with built-in SSL
- tunneling when going through a Web Proxy?
-
- Q-56: Can Apache web server act as a gateway for users to connect via
- SSL from the Internet with a Web browser to x11vnc running on their
- workstations behind a firewall?
-
- Q-57: Can I create and use my own SSL Certificate Authority (CA) with
- x11vnc?
-
- [Display Managers and Services]
-
- Q-58: How can I run x11vnc as a "service" that is always available?
-
- Q-59: How can I use x11vnc to connect to an X login screen like xdm,
- GNOME gdm, KDE kdm, or CDE dtlogin? (i.e. nobody is logged into an X
- session yet.)
-
- Q-60: Can I run x11vnc out of inetd(8)? How about xinetd(8)?
-
- Q-61: Can I have x11vnc advertise its VNC service and port via mDNS /
- Zeroconf (e.g. Avahi) so VNC viewers on the local network can detect
- it automatically?
-
- Q-62: Can I have x11vnc allow a user to log in with her UNIX username
- and password and then have it find her X session display on that
- machine and then attach to it? How about starting an X session if one
- cannot be found?
-
- Q-63: Can I have x11vnc restart itself after it terminates?
-
- Q-64: How do I make x11vnc work with the Java VNC viewer applet in a
- web browser?
-
- Q-65: Are reverse connections (i.e. the VNC server connecting to the
- VNC viewer) using "vncviewer -listen" and vncconnect(1) supported?
-
- Q-66: Can reverse connections be made to go through a Web or SOCKS
- proxy or SSH?
-
- Q-67: Can x11vnc provide a multi-user desktop web login service as an
- Apache CGI or PHP script?
-
- Q-68: Can I use x11vnc as a replacement for Xvnc? (i.e. not for a real
- display, but for a virtual one I keep around.)
-
- Q-69: How can I use x11vnc on "headless" machines? Why might I want
- to?
-
- [Resource Usage and Performance]
-
- Q-70: I have lots of memory, but why does x11vnc fail with shmget:
- No space left on device or Minor opcode of failed request: 1
- (X_ShmAttach)?
-
- Q-71: How can I make x11vnc use less system resources?
-
- Q-72: How can I make x11vnc use MORE system resources?
-
- Q-73: I use x11vnc over a slow link with high latency (e.g. dialup
- modem or broadband), is there anything I can do to speed things up?
-
- Q-74: Does x11vnc support the X DAMAGE Xserver extension to find
- modified regions of the screen quickly and efficiently?
-
- Q-75: My OpenGL application shows no screen updates unless I supply
- the -noxdamage option to x11vnc.
-
- Q-76: When I drag windows around with the mouse or scroll up and down
- things really bog down (unless I do the drag in a single, quick
- motion.) Is there anything to do to improve things?
-
- Q-77: Why not do something like wireframe animations to avoid the
- windows "lurching" when being moved or resized?
-
- Q-78: Can x11vnc try to apply heuristics to detect when a window is
- scrolling its contents and use the CopyRect encoding for a speedup?
-
- Q-79: Can x11vnc do client-side caching of pixel data? I.e. so when
- that pixel data is needed again it does not have to be retransmitted
- over the network.
-
- Q-80: Does x11vnc support TurboVNC?
-
- [Mouse Cursor Shapes]
-
- Q-81: Why isn't the mouse cursor shape (the little icon shape where
- the mouse pointer is) correct as I move from window to window?
-
- Q-82: When using XFIXES cursorshape mode, some of the cursors look
- really bad with extra black borders around the cursor and other cruft.
- How can I improve their appearance?
-
- Q-83: In XFIXES mode, are there any hacks to handle cursor
- transparency ("alpha channel") exactly?
-
- [Mouse Pointer]
-
- Q-84: Why does the mouse arrow just stay in one corner in my
- vncviewer, whereas my cursor (that does move) is just a dot?
-
- Q-85: Can I take advantage of the TightVNC extension to the VNC
- protocol where Cursor Positions Updates are sent back to all connected
- clients (i.e. passive viewers can see the mouse cursor being moved
- around by another viewer)?
-
- Q-86: Is it possible to swap the mouse buttons (e.g. left-handed
- operation), or arbitrarily remap them? How about mapping button clicks
- to keystrokes, e.g. to partially emulate Mouse wheel scrolling?
-
- [Keyboard Issues]
-
- Q-87: How can I get my AltGr and Shift modifiers to work between
- keyboards for different languages?
-
- Q-88: When I try to type a "<" (i.e. less than) instead I get ">"
- (i.e. greater than)! Strangely, typing ">" works OK!!
-
- Q-89: Extra Character Inserted, E.g.: When I try to type a "<" (i.e.
- less than) instead I get "<," (i.e. an extra comma.)
-
- Q-90: I'm using an "international" keyboard (e.g. German "de", or
- Danish "dk") and the -modtweak mode works well if the VNC viewer is
- run on a Unix/Linux machine with a similar keyboard. But if I run
- the VNC viewer on Unix/Linux with a different keyboard (e.g. "us") or
- Windows with any keyboard, I can't type some keys like: "@", "$",
- "<", ">", etc. How can I fix this?
-
- Q-91: When typing I sometimes get double, triple, or more of my
- keystrokes repeated. I'm sure I only typed them once, what can I do?
-
- Q-92: The x11vnc -norepeat mode is in effect, but I still get repeated
- keystrokes!!
-
- Q-93: After using x11vnc for a while, I find that I cannot type some
- (or any) characters or my mouse clicks and drags no longer have any
- effect, or they lead to strange effects. What happened?
-
- Q-94: The machine where I run x11vnc has an AltGr key, but the local
- machine where I run the VNC viewer does not. Is there a way I can map
- a local unused key to send an AltGr? How about a Compose key as well?
-
- Q-95: I have a Sun machine I run x11vnc on. Its Sun keyboard has just
- one Alt key labelled "Alt" and two Meta keys labelled with little
- diamonds. The machine where I run the VNC viewer only has Alt keys.
- How can I send a Meta keypress? (e.g. emacs needs this)
-
- Q-96: Running x11vnc on HP-UX I cannot type "#" I just get a "3"
- instead.
-
- Q-97: Can I map a keystroke to a mouse button click on the remote
- machine?
-
- Q-98: How can I get Caps_Lock to work between my VNC viewer and
- x11vnc?
-
- [Screen Related Issues and Features]
-
- Q-99: The remote display is larger (in number of pixels) than the
- local display I am running the vncviewer on. I don't like the
- vncviewer scrollbars, what I can do?
-
- Q-100: Does x11vnc support server-side framebuffer scaling? (E.g. to
- make the desktop smaller.)
-
- Q-101: Does x11vnc work with Xinerama? (i.e. multiple monitors joined
- together to form one big, single screen.)
-
- Q-102: Can I use x11vnc on a multi-headed display that is not Xinerama
- (i.e. separate screens :0.0, :0.1, ... for each monitor)?
-
- Q-103: Can x11vnc show only a portion of the display? (E.g. for a
- special purpose application or a very large screen.)
-
- Q-104: Does x11vnc support the XRANDR (X Resize, Rotate and
- Reflection) extension? Whenever I rotate or resize the screen x11vnc
- just seems to crash.
-
- Q-105: Independent of any XRANDR, can I have x11vnc rotate and/or
- reflect the screen that the VNC viewers see? (e.g. for a handheld
- whose screen is rotated 90 degrees.)
-
- Q-106: Why is the view in my VNC viewer completely black? Or why is
- everything flashing around randomly?
-
- Q-107: I use Linux Virtual Terminals (VT's) to implement 'Fast User
- Switching' between users' sessions (e.g. Betty is on Ctrl-Alt-F7,
- Bobby is on Ctrl-Alt-F8, and Sid is on Ctrl-Alt-F1: they use those
- keystrokes to switch between their sessions.) How come the view in a
- VNC viewer connecting to x11vnc is either completely black or
- otherwise all messed up unless the X session x11vnc is attached to is
- in the active VT?
-
- Q-108: I am using x11vnc where my local machine has "popup/hidden
- taskbars" and the remote display where x11vnc runs also has
- "popup/hidden taskbars" and they interfere and fight with each other.
- What can I do?
-
- Q-109: Help! x11vnc and my KDE screensaver keep switching each other
- on and off every few seconds.
-
- Q-110: I am running the compiz 3D window manager (or beryl, MythTv,
- Google Earth, or some other OpenGL app) and I do not get screen
- updates in x11vnc.
-
- Q-111: Can I use x11vnc to view my VMWare session remotely?
-
- [Exporting non-X11 devices via VNC]
-
- Q-112: Can non-X devices (e.g. a raw framebuffer) be viewed (and even
- controlled) via VNC with x11vnc?
-
- Q-113: Can I export the Linux Console (Virtual Terminals) via VNC
- using x11vnc?
-
- Q-114: Can I export via VNC a Webcam or TV tuner framebuffer using
- x11vnc?
-
- Q-115: Can I connect via VNC to a Qt-embedded/Qt-enhanced/Qtopia
- application running on my handheld, cell phone, or PC using the Linux
- console framebuffer (i.e. not X11)?
-
- Q-116: How do I inject touch screen input into an
- Qt-embedded/Qt-enhanced/Qtopia cell phone such as openmoko/qtmoko Neo
- Freerunner?
-
- Q-117: Now that non-X11 devices can be exported via VNC using x11vnc,
- can I build it with no dependencies on X11 header files and libraries?
-
- Q-118: How do I cross compile x11vnc for a different architecture than
- my Linux i386 or amd64 PC?
-
- Q-119: Does x11vnc support Mac OS X Aqua/Quartz displays natively
- (i.e. no X11 involved)?
-
- Q-120: Can x11vnc be used as a VNC reflector/repeater to improve
- performance for the case of a large number of simultaneous VNC viewers
- (e.g. classroom broadcasting or a large demo)?
-
- Q-121: Can x11vnc be used during a Linux, Solaris, etc. system
- Installation so the Installation can be done remotely?
-
- [Misc: Clipboard, File Transfer/Sharing, Printing, Sound, Beeps,
- Thanks, etc.]
-
- Q-122: Does the Clipboard/Selection get transferred between the
- vncviewer and the X display?
-
- Q-123: Can I use x11vnc to record a Shock Wave Flash (or other format)
- video of my desktop, e.g. to record a tutorial or demo?
-
- Q-124: Can I transfer files back and forth with x11vnc?
-
- Q-125: Which UltraVNC extensions are supported?
-
- Q-126: Can x11vnc emulate UltraVNC's Single Click helpdesk mode for
- Unix? I.e. something very simple for a naive user to initiate a
- reverse vnc connection from their Unix desktop to a helpdesk
- operator's VNC Viewer.
-
- Q-127: Can I (temporarily) mount my local (viewer-side) Windows/Samba
- File share on the machine where x11vnc is running?
-
- Q-128: Can I redirect CUPS print jobs from the remote desktop where
- x11vnc is running to a printer on my local (viewer-side) machine?
-
- Q-129: How can I hear the sound (audio) from the remote applications
- on the desktop I am viewing via x11vnc?
-
- Q-130: Why don't I hear the "Beeps" in my X session (e.g. when typing
- tput bel in an xterm)?
-
- Q-131: Does x11vnc work with IPv6?
-
- Q-132: Thanks for your program or for your help! Can I make a
- donation?
- _________________________________________________________________
-
-
- [Building and Starting]
-
- Q-1: I can't get x11vnc to start up. It says "XOpenDisplay failed
- (null)" or "Xlib: connection to ":0.0" refused by server Xlib: No
- protocol specified" and then exits. What do I need to do?
-
- For the former error, you need to specify the X display to connect to
- (it also needs to be on the same machine the x11vnc process is to run
- on.) Set your DISPLAY environment variable (or use the -display
- option) to specify it. Nearly always the correct value will be ":0"
- (in fact, x11vnc will now assume :0 if given no other information.)
-
-
- For the latter error, you need to set up the X11 permissions
- correctly.
-
- To make sure X11 permissions are the problem do this simple test:
- while sitting at the physical X display open a terminal window
- (gnome-terminal, xterm, etc.) You should be able to run x11vnc
- successfully without any need for special steps or command line
- options in that terminal (i.e. just type "x11vnc".) If that works OK
- then you know X11 permissions are the only thing preventing it from
- working when you try to start x11vnc via, say, a remote shell.
-
- How to Solve: See the xauth(1), Xsecurity(7), and xhost(1) man pages
- or this Howto for much info on X11 permissions. For example, you may
- need to set your XAUTHORITY environment variable (or use the -auth
- option) to point to the correct MIT-MAGIC-COOKIE file (e.g.
- /home/joe/.Xauthority or /var/gdm/:0.Xauth or /var/lib/kdm/A:0-crWk72K
- or /tmp/.gdmzndVlR, etc, etc.), or simply be sure you run x11vnc as
- the correct user (i.e. the user who is logged into the X session you
- wish to view.)
-
- Note: The MIT cookie file contains the secret key that allows x11vnc
- to connect to the desired X display.
-
- If, say, sshd has set XAUTHORITY to point to a random file it has
- created for X forwarding that will cause problems. (Under some
- circumstances even su(1) and telnet(1) can set XAUTHORITY. See also
- the gdm parameter NeverPlaceCookiesOnNFS that sets XAUTHORITY to a
- random filename in /tmp for the whole X session.)
-
- Running x11vnc as root is often not enough: you need to know where the
- MIT-MAGIC-COOKIE file for the desired X display is.
-
- Example solution:
- x11vnc -display :0 -auth /var/gdm/:0.Xauth
-
- (this is for the display manager gdm and requires root permission to
- read the gdm cookie file, see this faq for other display manager
- cookie file names.)
-
- Note as of Feb/2007 you can also try the -find option instead of
- "-display ..." and see if that finds your display and Xauthority.
-
- Less safe, but to avoid figuring out where the correct XAUTHORITY file
- is, if the person sitting at the physical X session types "xhost
- +localhost" then one should be able to attach x11vnc to the session
- (from the same machine.) The person could then type "xhost -localhost"
- after x11vnc has connected to go back to the default permissions.
- Also, for some situations the "-users lurk=" option may soon be of use
- (please read the documentation on the -users option.)
-
- To test out your X11 permissions from a remote shell, set DISPLAY and
- possibly XAUTHORITY (see your shell's man page, bash(1), tcsh(1), on
- how to set environment variables) and type xdpyinfo in the same place
- you will be typing (or otherwise running) x11vnc. If information is
- printed out about the X display (screen sizes, supported extensions,
- color visuals info) that means the X11 permissions are set up
- properly: xdpyinfo successfully connected to DISPLAY! You could also
- type xclock and make sure no errors are reported (a clock should
- appear on the X display, press Ctrl-C to stop it.) If these work, then
- typing "x11vnc" in the same environment should also work.
-
- Important: if you cannot get your X11 permissions so that the xdpyinfo
- or xclock tests work, x11vnc also will not work (all of these X
- clients must be allowed to connect to the X server to function
- properly.)
-
- Firewalls: Speaking of permissions, it should go without saying that
- the host-level firewall will need to be configured to allow
- connections in on a port. E.g. 5900 (default VNC port) or 22 (default
- SSH port for tunnelling VNC.) Most systems these days have firewalls
- turned on by default, so you will actively have to do something to
- poke a hole in the firewall at the desired port number. See your
- system administration tool for Firewall settings (Yast, Firestarter,
- etc.)
-
-
- Q-2: I can't get x11vnc and/or libvncserver to compile.
-
- Make sure you have gcc (or other C compiler) and all of the required
- libraries and the corresponding -dev/-devel packages installed. These
- include Xorg/XFree86, libX11, libjpeg, libz, libssl, ... and don't
- forget the devs: libjpeg-dev, libssl-dev ...
-
- The most common build problem that people encounter is that the
- necessary X11 libraries are installed on their system however it does
- not have the corresponding -dev/-devel packages installed. These dev
- packages include C header files and build-time .so symlink. It is a
- shame the current trend in distros is to not install the dev package
- by default when the the library runtime package is installed... (it
- diminishes the power of open source)
-
- As of Nov/2006 here is a list of libraries that x11vnc usually likes
- to use:
-libc.so libX11.so libXtst.so libXext.so
-libXfixes.so libXdamage.so libXinerama.so libXrandr.so
-libz.so libjpeg.so libpthread.so
-libssl.so libcrypto.so libcrypt.so
-
- although x11vnc will be pretty usable with the subset: libc.so,
- libX11.so, libXtst.so, libXext.so, libz.so, and libjpeg.so.
-
- After running the libvncserver configure, carefully examine the output
- and the messages in the config.log file looking for missing
- components. For example, if the configure output looks like:
- checking how to run the C preprocessor... gcc -E
- checking for X... no
- checking for XkbSelectEvents in -lX11... no
- checking for XineramaQueryScreens in -lXinerama... no
- checking for XTestFakeKeyEvent in -lXtst... no
-
- or even worse:
- checking for C compiler default output file name... configure: error:
- C compiler cannot create executables
- See `config.log' for more details.
-
- there is quite a bit wrong with the build environment. Hopefully
- simply adding -dev packages and/or gcc or make will fix it.
-
- For Debian the list seems to be:
- gcc
- make
- libc6-dev
- libjpeg8-dev (formerly libjpeg62-dev)
- libx11-dev
- x11proto-core-dev (formerly x-dev)
- libxext-dev
- libxtst-dev
- libxdamage-dev
- libxfixes-dev
- libxrandr-dev
- libxinerama-dev
- libxss-dev (formerly xlibs-static-dev)
- zlib1g-dev
- libssl-dev
- libavahi-client-dev
- linux-libc-dev (only needed for linux console rawfb support)
-
- Note that depending on your OS version the above names may have been
- changed and/or additional packages may be needed.
-
- For Redhat the list seems to be:
- gcc
- make
- glibc-devel
- libjpeg-devel
- libX11-devel
- xorg-x11-proto-devel
- libXdamage-devel
- libXfixes-devel
- libXrandr-devel
- zlib-devel
- openssl-devel
- avahi-devel
- kernel-headers (only needed for linux console rawfb support)
-
- For other distros or OS's the package names may not be the same but
- will look similar. Also, distros tend to rename packages as well so
- the above list may be out of date. So only use the above lists as
- hints for the package names that are needed.
-
- Have a look at Misc. Build Problems for additional fixes.
-
- Note: there is growing trend in Linux and other distros to slice up
- core X11 software into more and smaller packages. So be prepared for
- more headaches compiling software...
-
-
- Q-3: I just built x11vnc successfully, but when I use it my keystrokes
- and mouse button clicks are ignored (I am able to move the mouse
- though.)
-
- This is most likely due to you not having a working build environment
- for the XTEST client library libXtst.so. The library is probably
- present on your system, but the package installing the build header
- file is missing.
-
- If you were watching carefully while configure was running you would
- have seen:
- checking for XTestFakeKeyEvent in -lXtst... no
-
- The solution is to add the necessary build environment package (and
- the library package if that is missing too.) On Debian the build
- package is libxtst-dev. Other distros/OS's may have it in another
- package.
-
- x11vnc will build without support for this library (e.g. perhaps one
- wants a view-only x11vnc on a stripped down or embedded system...) And
- at runtime it will also continue to run even if the X server it
- connects to does not support XTEST. In both cases it cannot inject
- keystrokes or button clicks since XTEST is needed for that (it can
- still move the mouse pointer using the X API XWarpPointer().)
-
- You will see a warning message something like this at run time:
- 20/03/2005 22:33:09 WARNING: XTEST extension not available (either missing fr
-om
- 20/03/2005 22:33:09 display or client library libXtst missing at build time
-.)
- 20/03/2005 22:33:09 MOST user input (pointer and keyboard) will be DISCARDE
-D.
- 20/03/2005 22:33:09 If display does have XTEST, be sure to build x11vnc wit
-h
- 20/03/2005 22:33:09 a working libXtst build environment (e.g. libxtst-dev,
- 20/03/2005 22:33:09 or other packages.)
- 20/03/2005 22:33:09 No XTEST extension, switching to -xwarppointer mode for
- 20/03/2005 22:33:09 pointer motion input.
-
- Also, as of Nov/2006 there will be a configure build time warning as
- well:
- ...
- checking for XFixesGetCursorImage in -lXfixes... yes
- checking for XDamageQueryExtension in -lXdamage... yes
- configure: WARNING:
- ==========================================================================
- A working build environment for the XTEST extension was not found (libXtst).
- An x11vnc built this way will be only barely usable. You will be able to
- move the mouse but not click or type. There can also be deadlocks if an
- application grabs the X server.
-
- It is recommended that you install the necessary development packages
- for XTEST (perhaps it is named something like libxtst-dev) and run
- configure again.
- ==========================================================================
-
-
- Q-4: Help, I need to run x11vnc on Solaris 2.5.1 (or other old
- Unix/Linux) and it doesn't compile!
-
- We apologize that x11vnc does not build cleanly on older versions of
- Solaris, Linux, etc.: very few users are on these old releases.
-
- We have heard that since Dec/2004 a Solaris 2.6 built x11vnc will run
- on Solaris Solaris 2.5 and 2.5.1 (since a workaround for XConvertCase
- is provided.)
-
- In any event, here is a workaround for Solaris 2.5.1 (and perhaps
- earlier and perhaps non-Solaris):
-
- First use the environment settings (CPPFLAGS, LDFLAGS, etc.) in the
- above Solaris build script to run the configure command. That should
- succeed without failure. Then you have to hand edit the autogenerated
- rfb/rfbconfig.h file in the source tree, and just before the last
- #endif at the bottom of that file insert these workaround lines:
-struct timeval _tmp_usleep_tv;
-#define usleep(x) \
- _tmp_usleep_tv.tv_sec = (x) / 1000000; \
- _tmp_usleep_tv.tv_usec = (x) % 1000000; \
- select(0, NULL, NULL, NULL, &_tmp_usleep_tv);
-int gethostname(char *name, int namelen);
-long random();
-int srandom(unsigned int seed);
-#undef LIBVNCSERVER_HAVE_LIBPTHREAD
-#define SHUT_RDWR 2
-typedef unsigned int in_addr_t;
-#define snprintf(a, n, args...) sprintf((a), ## args)
-
- Then run make with the Solaris build script environment, everything
- should compile without problems, and the resulting x11vnc binary
- should work OK. If some non-x11vnc related programs fail (e.g. test
- programs) and the x11vnc binary is not created try "make -k" to have
- it keep going. Similar sorts of kludges in rfb/rfbconfig.h can be done
- on other older OS (Solaris, Linux, ...) releases.
-
- Here are some notes for similar steps that need to be done to build on
- SunOS 4.x
-
- Please let us know if you had to use the above workaround (and whether
- it worked or not.) If there is enough demand we will try to push clean
- compilations back to earlier Solaris, Linux, etc, releases.
-
-
- Q-5: Where can I get a precompiled x11vnc binary for my Operating
- System?
-
- Hopefully the build steps above and FAQ provide enough info for a
- painless compile for most environments. Please report problems with
- the x11vnc configure, make, etc. on your system (if your system is
- known to compile other GNU packages successfully.)
-
- There are precompiled x11vnc binaries built by other groups that are
- available at the following locations:
- Slackware: (.tgz) http://www.linuxpackages.net/
-
- SuSE: (.rpm) http:/software.opensuse.org/ Gentoo: (info)
- http://gentoo-wiki.com/ and http://gentoo-portage.com/ FreeBSD: (.tbz)
- http://www.freebsd.org/ http://www.freshports.org/net/x11vnc NetBSD:
- (src) http://pkgsrc.se/x11/x11vnc OpenBSD: (.tgz) http://openports.se/
- Arch Linux: (.tgz) http://www.archlinux.org/ Nokia 770 (.deb)
- http://mike.saunby.googlepages.com/x11vncfornokia7702 Sharp Zaurus
- http://www.focv.com/ Debian: (.deb) http://packages.debian.org/x11vnc
- Redhat/Fedora: (.rpm) http://packages.sw.be/x11vnc RPMforge
- http://dag.wieers.com/rpm/packages/x11vnc/ (N.B.: unmaintained after
- 0.9.3) Solaris: (pkg) http://www.sunfreeware.com/
-
- If the above binaries don't work and building x11vnc on your OS fails
- (and all else fails!) you can try one of My Collection of x11vnc
- Binaries for various OS's and x11vnc releases.
-
- As a general note, the x11vnc program is simple enough you don't
- really need to install a package: the binary will in most cases work
- as is and from any location (as long as your system libraries are not
- too old, etc.) So, for Linux distributions that are not one of the
- above, the x11vnc binary from the above packages has a good chance of
- working. You can "install" it by just copying the x11vnc binary to the
- desired directory in your PATH. Tip on extracting files from a Debian
- package: extract the archive via a command like: "ar x
- x11vnc_0.6-2_i386.deb" and then you can find the binary in the
- resulting data.tar.gz tar file. Also, rpm2cpio(1) is useful in
- extracting files from rpm packages.
-
- If you use a standalone binary like this and also want x11vnc to serve
- up the Java VNC Viewer jar file (either SSL enabled or regular one),
- then you will need to extract the classes subdirectory from the source
- tarball and point x11vnc to it via the -httpdir option. E.g.:
- x11vnc -httpdir /path/to/x11vnc-0.9.9/classes/ssl ...
-
-
- Q-6: Where can I get a VNC Viewer binary (or source code) for the
- Operating System I will be viewing from?
-
- To obtain VNC viewers for the viewing side (Windows, Mac OS, or Unix)
- try here:
- * http://www.tightvnc.com/download.html
- * http://www.realvnc.com/download-free.html
- * http://sourceforge.net/projects/cotvnc/
- * http://www.ultravnc.com/
- * Our Enhanced TightVNC Viewer (SSVNC)
-
- [ssvnc.gif]
-
-
- Q-7: How can I see all of x11vnc's command line options and
- documentation on how to use them?
-
- Run: x11vnc -opts to list just the option names or run: x11vnc
- -help for long descriptions about each option. The output is listed
- here as well. Yes, x11vnc does have a lot of options, doesn't it...
-
-
- Q-8: I don't like typing arcane command line options every time I
- start x11vnc. What can I do? Is there a config file? Or a GUI?
-
- You could create a shell script that calls x11vnc with your options:
-#!/bin/sh
-#
-# filename: X11vnc (i.e. not "x11vnc")
-# It resides in a directory in $PATH. "chmod 755 X11vnc" has been run on it.
-#
-x11vnc -wait 50 -localhost -rfbauth $HOME/.vnc/passwd -display :0 $*
-
- a similar thing can be done via aliases in your shell (bash, tcsh,
- csh, etc..)
-
- Or as of Jun/2004 you can use the simple $HOME/.x11vncrc config file
- support. If that file exists, each line is taken as a command line
- option. E.g. the above would be:
-# this is a comment in my ~/.x11vncrc file
-wait 50 # this is a comment to the end of the line.
--localhost # note: the leading "-" is optional.
-rfbauth /home/fred/.vnc/passwd
-display :0
-
- As of Dec/2004 there is now a simple Tcl/Tk GUI based on the
- remote-control functionality ("-R") that was added. The /usr/bin/wish
- program is needed for operation. The gui is not particularly
- user-friendly, it just provides a point and click mode to set all the
- many x11vnc parameters and obtain help on them. It is also very useful
- for testing. See the -gui option for more info. Examples: "x11vnc ...
- -gui" and "x11vnc ... -gui other:0" in the latter case the gui is
- displayed on other:0, not the X display x11vnc is polling. There is
- also a "-gui tray" system tray mode.
-
- [tkx11vnc.gif]
-
- NOTE: You may need to install the "wish" or "tk" or "tk8.4" package
- for the gui mode to work (the package name depends on your OS/distro.)
- The tcl/tk "wish" interpreter is used. In debian (and so ubuntu too)
- one would run "apt-get install tk" or perhaps "apt-get install tk8.4"
-
-
- Q-9: How can I get the GUI to run in the System Tray, or at least be a
- smaller, simpler icon?
-
- As of Jul/2005 the gui can run in a more friendly small icon mode
- "-gui icon" or in the system tray: "-gui tray". It has balloon status,
- a simple menu, and a Properities dialog. The full, complicated, gui is
- only available under "Advanced". Other improvements were added as
- well. Try "Misc -> simple_gui" for a gui with fewer esoteric menu
- items.
-
- If the gui fails to embed itself in the system tray, do a retry via
- "Window View -> icon" followed by "Window View -> tray" with the popup
- menu.
-
- For inexperienced users starting up x11vnc and the GUI while sitting
- at the physical X display (not remotely), using something like "x11vnc
- -display :0 -gui tray=setpass" might be something for them that they
- are accustomed to in a Desktop environment (it prompts for an initial
- password, etc.) This is a basic "Share My Desktop" usage mode.
-
- As of Nov/2008 in x11vnc 0.9.6 there is a desktop menu item
- (x11vnc.desktop) that runs this command:
- x11vnc -gui tray=setpass -rfbport PROMPT -logfile %HOME/.x11vnc.log.%VNCDISP
-LAY
-
- which also prompts for which VNC port to use and a couple other
- parameters.
-
-
- Q-10: How can I get x11vnc to listen on a different port besides the
- default VNC port (5900)?
-
- Use something like, e.g., "x11vnc -rfbport 5901" to force it to use
- port 5901 (this is VNC display :1.) If something else is using that
- port x11vnc will exit immediately. If you do not supply the -rfbport
- option, it will autoprobe starting at 5900 and work its way up to 5999
- looking for a free port to listen on. In that case, watch for the
- PORT=59xx line to see which port it found, then subtract 5900 from it
- for the VNC display number to enter into the VNC Viewer(s).
-
- The "-N" option will try to match the VNC display number to the X
- display (e.g. X11 DISPLAY of :5 (port 6005) will have VNC display :5
- (port 5905).)
-
- Also see the "-autoport n" option to indicated at which value the auto
- probing should start at.
-
-
- Q-11: My Firewall/Router doesn't allow VNC Viewers to connect to
- x11vnc.
-
- See the Firewalls/Routers discussion.
-
-
- Q-12: Is it possible for a VNC Viewer and a VNC Server to connect to
- each other even though both are behind Firewalls that block all
- incoming connections?
-
- This is very difficult or impossible to do unless a third machine,
- reachable by both, is used as a relay. So we assume a third machine is
- somehow being used as a relay.
-
- (Update: It may be possible to do "NAT-2-NAT" without a relay machine
- by using a UDP tunnel such as http://samy.pl/pwnat/. All that is
- required is that both NAT firewalls allow in UDP packets from an IP
- address to which a UDP packet has recently been sent to. If you try it
- out let us know how it went.)
-
- In the following discussion, we will suppose port 5950 is being used
- on the relay machine as the VNC port for the rendezvous.
-
- A way to rendezvous is to have the VNC Server start a reverse
- connection to the relay machine:
- x11vnc -connect third-machine.net:5950 ...
-
- and the VNC viewer forward connects as usual:
- vncviewer third-machine.net:50
-
- Or maybe two ports would be involved, e.g. the viewer goes to display
- :51 (5951.) It depends on the relay software being used.
-
- What software to run on third-machine? A TCP relay of some sort could
- be used... Try a google search on "tcp relay" or "ip relay". However,
- note that this isn't a simple redirection because it hooks up two
- incoming connections. You can look at our UltraVNC repeater
- implementation ultravnc_repeater.pl for ideas and possibly to
- customize.
-
- Also, if you are not the admin of third-machine you'd have to convince
- the owner to allow you to install this software (and he would likely
- need to open his server's firewall to allow the port through.)
-
- It is recommended that SSL is used for encryption (e.g. "-ssl SAVE")
- when going over the internet.
-
- We have a prototype for performing a rendezvous via a Web Server
- acting as the relay machine. Download the vncxfer CGI script and see
- the instructions at the top.
-
- Once that CGI script is set up on the website, both users go to, say,
- http://somesite.com/vncxfer (or maybe a "/cgi-bin" directory or ".cgi"
- suffix must be used.) Previously, both have agreed on the same session
- name (say by phone or email) , e.g. "5cows", and put that into the
- entry form on the vncxfer starting page (hopefully separated by a few
- seconds, so the relay helper can fully start up at the first request.)
-
- The page returned tells them the hostname and port number and possible
- command to use for forward (VNC Viewer) and reverse (VNC Server, i.e.
- x11vnc) connections as described above.
-
- Also since Oct/2007, x11vnc can connect directly (no web browser),
- like this:
- x11vnc ... -connect localhost:0 -proxy 'http://somesite.com/vncxfer?session=
-5cows&'
-
- Unfortunately the prototype requires that the Web server's firewall
- allow in the port (e.g. 5950) used for the rendezvous. Most web
- servers are not configured to do this, so you would need to ask the
- admin to do this for you. Nearly all free webspace sites, e.g.
- www.zendurl.com, will not allow your CGI script to be an open relay
- like this. (If you find one that does allow this, let me know!)
-
- Maybe someday a clever trick will be thought up to relax the listening
- port requirement (e.g. use HTTP/CGI itself for the transfer... it is
- difficult to emulate a full-duplex TCP connection with them.)
-
- See also the Firewalls/Routers discussion and Reverse Connection Proxy
- discussion.
-
-
- SSH method: If both users (i.e. one on Viewer-side and the other on
- x11vnc server side) have SSH access to a common machine on the
- internet (or otherwise mutually reachable), then SSH plumbing can be
- used to solve this problem. The users create SSH tunnels going through
- the SSH login machine.
-
- Instead of assuming port 5900 is free on the SSH machine, we will
- assume both users agreed to use 5933. This will illustrate how to use
- a different port for the redir. It could be any port, what matters is
- that both parties refer to the same one.
-
- Set up the Tunnel from the VNC Server side:
- ssh -t -R 5933:localhost:5900 user@third-machine.net
-
- Set up the Tunnel from the VNC Viewer side:
- ssh -t -L 5900:localhost:5933 user@third-machine.net
-
- Run Server on the VNC Server side:
- x11vnc -rfbport 5900 -localhost ...
-
- Run Viewer on the VNC Viewer side:
- vncviewer -encodings "copyrect tight zrle hextile" localhost:0
-
- (we assume the old-style -encodings option needs to be used. See here
- for details.)
-
- If the SSH machine has been configured (see sshd_config(5)) with the
- option GatewayPorts=yes, then the tunnel set up by the VNC Server will
- be reachable directly by the VNC viewer (as long as the SSH machine's
- firewall does not block the port, 5933 in this example.) So in that
- case the Viewer side does not need to run any ssh command, but rather
- only runs:
- vncviewer third-machine.net:33
-
- In this case we recommend SSL be used for encryption.
-
- The creation of both tunnels can be automated. As of Oct/2007 the -ssh
- x11vnc option is available and so only this command needs to be run on
- the VNC Server side:
- x11vnc -ssh user@third-machine.net:33 ...
-
- (the SSH passphrase may need to be supplied.)
-
- To automate on the VNC Viewer side, the user can use the Enhanced
- TightVNC Viewer (SSVNC) by:
- * Clicking on 'Use SSH'
- * Entering user@third-machine.net:33 into 'VNC Host:Display' entry
- box
- * Clicking on 'Connect'
-
- As above, if the SSH GatewayPorts=yes setting is configured the Viewer
- side doesn't need to create a SSH tunnel. In SSVNC the Viewer user
- could instead select 'Use SSL' and then, e.g., on the Server side
- supply "-ssl SAVE" to x11vnc. Then end-to-end SSL encryption would be
- used (in addition to the SSH encryption on the Server-side leg.)
-
-
- Q-13: Can I make x11vnc more quiet and also go into the background
- after starting up?
-
- Use the -q and -bg options, respectively. (also: -quiet is an alias
- for -q)
-
- Note that under -bg the stderr messages will be lost unless you use
- the "-o logfile" option.
-
-
- Q-14: Sometimes when a VNC viewer dies abruptly, x11vnc also dies with
- the error message like: "Broken pipe". I'm using the -forever mode and
- I want x11vnc to keep running.
-
- As of Jan/2004 the SIGPIPE signal is ignored. So if a viewer client
- terminates abruptly, libvncserver will notice on the next I/O
- operation and will close the connection and continue on.
-
- Up until of Apr/2004 the above fix only works for BSD signal systems
- (Linux, FreeBSD, ...) For SYSV systems there is a workaround in place
- since about Jun/2004.
-
-
- Q-15: The Windows TightVNC 1.3.9 Viewer cannot connect to x11vnc.
-
- This appears to be fixed in x11vnc version 0.9 and later. If you need
- to use an earlier version of x11vnc, try using the "-rfbversion 3.7"
- option. In general sometimes one can get a misbehaving viewer to work
- by supplying rfb versions 3.7 or 3.3.
-
-
- Q-16: KDE's krdc VNC viewer cannot connect to x11vnc.
-
- This has been fixed in x11vnc version 0.8.4. More info here, here, and
- here.
-
-
- Q-17: When I start x11vnc on an Alpha Tru64 workstation the X server
- crashes!
-
- This is a bug in the X server obviously; an X client should never be
- able to crash it.
-
- The problem seems to be with the RECORD X extension and so a
- workaround is to use the "-noxrecord" x11vnc command line option.
-
-
- Q-18: When running x11vnc on an IBM AIX workstation after a few
- minutes the VNC connection freezes.
-
- One user reports when running x11vnc on AIX 5.3 in his CDE session
- after a few minutes or seconds x11vnc will "freeze" (no more updates
- being sent, etc.) The freezing appeared to be worse for versions later
- than 0.9.2.
-
- The problem seems to be with the RECORD X extension on AIX and so a
- workaround is to use the "-noxrecord" x11vnc command line option. The
- user found no freezes occurred when using that option.
-
-
- Q-19: Are there any build-time customizations possible, e.g. change
- defaults, create a smaller binary, etc?
-
- There are some options. They are enabled by adding something like
- -Dxxxx=1 to the CPPFLAGS environment variable before running configure
- (see the build notes for general background.)
-/*
- * Mar/2006
- * Build-time customization via CPPFLAGS.
- *
- * Summary of options to include in CPPFLAGS for custom builds:
- *
- * -DVNCSHARED to have the vnc display shared by default.
- * -DFOREVER to have -forever on by default.
- * -DNOREPEAT=0 to have -repeat on by default.
- * -DADDKEYSYMS=0 to have -noadd_keysyms the default.
- *
- * -DREMOTE_DEFAULT=0 to disable remote-control on by default (-yesremote.)
- * -DREMOTE_CONTROL=0 to disable remote-control mechanism completely.
- * -DEXTERNAL_COMMANDS=0 to disable the running of all external commands.
- * -DFILEXFER=0 disable filexfer.
- *
- * -DHARDWIRE_PASSWD=... hardwired passwords, quoting necessary.
- * -DHARDWIRE_VIEWPASSWD=...
- * -DNOPW=1 make -nopw the default (skip warning)
- * -DUSEPW=1 make -usepw the default
- * -DPASSWD_REQUIRED=1 exit unless a password is supplied.
- * -DPASSWD_UNLESS_NOPW=1 exit unless a password is supplied and no -nopw.
- *
- * -DWIREFRAME=0 to have -nowireframe as the default.
- * -DWIREFRAME_COPYRECT=0 to have -nowirecopyrect as the default.
- * -DWIREFRAME_PARMS=... set default -wirecopyrect parameters.
- * -DSCROLL_COPYRECT=0 to have -noscrollcopyrect as the default.
- * -DSCROLL_COPYRECT_PARMS=... set default -scrollcopyrect parameters.
- * -DSCALING_COPYRECT=0
- * -DXDAMAGE=0 to have -noxdamage as the default.
- * -DSKIPDUPS=0 to have -noskip_dups as the default or vice versa.
- *
- * -DPOINTER_MODE_DEFAULT={0,1,2,3,4} set default -pointer_mode.
- * -DBOLDLY_CLOSE_DISPLAY=0 to not close X DISPLAY under -rawfb.
- * -DSMALL_FOOTPRINT=1 for smaller binary size (no help, no gui, etc)
- * use 2 or 3 for even smaller footprint.
- * -DNOGUI do not include the gui tkx11vnc.
- * -DPOLL_8TO24_DELAY=N
- * -DDEBUG_XEVENTS=1 enable printout for X events.
- *
- * Set these in CPPFLAGS before running configure. E.g.:
- *
- * % env CPPFLAGS="-DFOREVER -DREMOTE_CONTROL=0" ./configure
- * % make
- */
-
- If other things (e.g. "-I ...") are needed in CPPFLAGS add them as
- well.
-
- On some systems is seems you need to set LC_ALL=C for configure to
- work properly...
-
- Be careful the following two variables: HARDWIRE_PASSWD and
- HARDWIRE_VIEWPASSWD. If set (remember to include the double quotes
- around the string), they will be used as default values for the
- -passwd and -viewpasswd options. Of course the strings will exist
- unobscured in the x11vnc binary: it better not be readable by
- unintendeds. Perhaps this is of use in remote access for an embedded
- application, etc...
-
- Let us know if more build-time customizations would be useful.
-
-
- [Win2VNC Related]
-
- Q-20: I have two separate machine displays in front of me, one Windows
- the other X11: can I use x11vnc in combination with Win2VNC in
- dual-screen mode to pass the keystrokes and mouse motions to the X11
- display?
-
- Yes, for best response start up x11vnc with the "-nofb" option
- (disables framebuffer polling, and does other optimizations) on the
- secondary display (X11) machine. Then start up Win2VNC on the primary
- display (Windows) referring it to the secondary display.
-
- This will also work X11 to X11 using x2vnc, however you would probably
- just want to avoid VNC and use x2x for that.
-
- For reference, here are some links to Win2VNC-like programs for
- multiple monitor setups:
- * Original Win2VNC
- * Enhanced Win2VNC (broken?) and sourceforge link
- * x2vnc
- * x2x
- * zvnc (MorphOS)
-
- All of them will work with x11vnc (except x2x where it is not needed.)
-
-
- Q-21: I am running Win2VNC on my Windows machine and "x11vnc -nofb" on
- Unix to pass keyboard and mouse to the Unix monitor. Whenever I start
- Win2VNC it quickly disconnects and x11vnc says:
- rfbProcessClientNormalMessage: read: Connection reset by peer
-
- Is the default visual of the X display you run x11vnc on low color
- (e.g. 8 bit per pixel PseudoColor)? (you can run xdpyinfo to check,
- look in the "screen" section.) There seems to be a bug in Win2VNC in
- that it cannot deal correctly with colormaps (PseudoColor is the most
- common example of a visual with a colormap.)
-
- If so, there are a couple options. 1) Can you set the default visual
- on your display to be depth 24 TrueColor? Sun machines often have 8+24
- overlay/multi-depth visuals, and you can make the default visual depth
- 24 TrueColor (see fbconfig(1) and Xsun(1).) 2) As of Feb/2004 x11vnc
- has the -visual option to allow you to force the framebuffer visual to
- whatever you want (this usually messes up the colors unless you are
- very clever.) In this case, the option provides a convenient
- workaround for the Win2VNC bug:
- x11vnc -nofb -visual TrueColor -display :0 ...
-
- So the visual will be set to 8bpp TrueColor and Win2VNC can handle
- this. Since Win2VNC does not use the framebuffer data there should be
- no problems in doing this.
-
- Q-22: Can I run "x11vnc -nofb" on a Mac OS X machine to redirect mouse
- and keyboard input to it from Windows and X11 machines via Win2VNC and
- x2vnc, respectively?
-
- Yes, as of Nov/2006 you can. There may be a trick or two you'll need
- to do to get the Clipboard exchange between the machines to work.
-
-
-
- [Color Issues]
-
- Q-23: The X display I run x11vnc on is only 8 bits per pixel (bpp)
- PseudoColor (i.e. only 256 distinct colors.) The x11vnc colors may
- start out OK, but after a while they are incorrect in certain windows.
-
- Use the -flashcmap option to have x11vnc watch for changes in the
- colormap, and propagate those changes back to connected clients. This
- can be slow (since the whole screen must be updated over the network
- whenever the colormap changes.) This flashing colormap behavior often
- happens if an application installs its own private colormap when the
- mouse is in its window. "netscape -install" is a well-known historical
- example of this. Consider reconfiguring the system to 16 bpp or depth
- 24 TrueColor if at all possible.
-
- Also note the option -8to24 (Jan/2006) can often remove the need for
- flashing the colormap. Everything is dynamically transformed to depth
- 24 at 32 bpp using the colormaps. There may be painting errors however
- (see the following FAQ for tips on reducing and correcting them.)
-
- In some rare cases (SCO unixware) the -notruecolor option has
- corrected colors on 8bpp displays. The red, green, and blue masks were
- non-zero in 8bpp PseudoColor on an obscure setup, and this option
- corrected the problems.
-
-
- Q-24: Color problems: Why are the colors for some windows incorrect in
- x11vnc? BTW, my X display has nice overlay/multi-depth visuals of
- different color depths: e.g. there are both depth 8 and 24 visuals
- available at the same time.
-
- You may want to review the previous question regarding 8 bpp
- PseudoColor.
-
- On some hardware (Sun/SPARC and SGI), the -overlay option discussed a
- couple paragraphs down may solve this for you (you may want to skip to
- it directly.) On other hardware the less robust -8to24 option may help
- (also discussed below.)
-
- Run xdpyinfo(1) to see what the default visual is and what the depths
- of the other visuals are. Does the default visual have a depth of 8
- but there are other visuals of depth 24? If it does, can you possibly
- re-configure your X server to make a depth 24 visual the default? If
- you can do it, this will save you a lot of grief WRT colors and x11vnc
- (and for general usage too!) Here is how I do this on an old
- Sparcstation 20 running Solaris 9 with SX graphics
- xinit -- -dev /dev/fb defclass TrueColor defdepth 24
-
- and it works nicely (note: to log into console from the dtlogin
- window, select "Options -> Command Line Login", then login and enter
- the above command.) See the -dev section of the Xsun(1) manpage for a
- description of the above arguments. If you have root permission, a
- more permanent and convenient thing to do is to record the arguments
- in a line like:
- :0 Local local_uid@console root /usr/openwin/bin/Xsun -dev /dev/fb defclass
-TrueColor defdepth 24
-
- in /etc/dt/config/Xservers (copy /usr/dt/config/Xservers.) Also look
- at the fbconfig(1) and related manpages (e.g. ffbconfig, m64config,
- pgxconfig, SUNWjfb_config, etc ...) for hardware framebuffer settings
- that may achieve the same effect.
-
- In general for non-Sun machines, look at the "-cc class" and related
- options in your X server manpage (perhaps Xserver(1)), it may allow
- modifying the default visual (e.g. "-cc 4", see <X11/X.h> for the
- visual class numbers.) On XFree86 some video card drivers (e.g. Matrox
- mga) have settings like Option "Overlay" "24,8" to support multi-depth
- overlays. For these, use the "-cc 4" X server command line option to
- get a depth 24 default visual.
-
-
- The -overlay mode: Another option is if the system with overlay
- visuals is a Sun system running Solaris or SGI running IRIX you can
- use the -overlay x11vnc option (Aug/2004) to have x11vnc use the
- Solaris XReadScreen(3X11) function to poll the "true view" of the
- whole screen at depth 24 TrueColor. XReadDisplay(3X11) is used on
- IRIX. This is useful for Legacy applications (older versions of
- Cadence CAD apps are mentioned by x11vnc users) that require the
- default depth be 8bpp, or the app will use a 8bpp visual even if depth
- 24 visuals are available, and so the default depth workaround
- described in the previous paragraph is not sufficient for these apps.
-
- It seems that Xorg is working toward supporting XReadDisplay(3X11) as
- part of the RENDER extension work. When it does support it and
- provides a library API x11vnc will be modified to take advantage of
- the feature to support -overlay on Linux, *BSD, etc. Until then see
- the -8to24 mode below.
-
- Misc. notes on -overlay mode: An amusing by-product of -overlay mode
- is that the mouse cursor shape is correct! (i.e. XFIXES is not
- needed.) The -overlay mode may be somewhat slower than normal mode due
- to the extra framebuffer manipulations that must be performed. Also,
- on Solaris there is a bug in that for some popup menus, the windows
- they overlap will have painting errors (flashing colors) while the
- popup is up (a workaround is to disable SaveUnders by passing -su to
- Xsun, e.g. in your /etc/dt/config/Xservers file.)
-
-
- The -8to24 mode: The -8to24 x11vnc option (Jan/2006) is a kludge to
- try to dynamically rewrite the pixel values so that the 8bpp part of
- the screen is mapped onto depth 24 TrueColor. This is less robust than
- the -overlay mode because it is done by x11vnc outside of the X
- server. So only use it on OS's that do not support -overlay. The
- -8to24 mode will work if the default visual is depth 24 or depth 8. It
- scans for any windows within 3 levels of the root window that are 8bpp
- (i.e. legacy application), or in general ones that are not using the
- default visual. For the windows it finds it uses XGetSubImage() to
- retrieve the pixels values and uses the correct indexed colormap to
- create a depth 24 TrueColor view of the whole screen. This depth 24,
- 32bpp view is exported via VNC.
-
- Even on pure 8bpp displays it can be used as an alternative to
- -flashcmap to avoid color flashing completely.
-
- This scheme is approximate and can often lead to painting errors. You
- can manually correct most painting errors by pressing 3 Alt_L's in a
- row, or by using something like: -fixscreen V=3.0 to automatically
- refresh the screen every 3 seconds. Also -fixscreen 8=3.0 has been
- added to just refresh the non-default visual parts of the screen.
-
- In general the scheme uses many resources and may give rise to
- sluggish behavior. If multiple windows are using different 8bpp
- indexed colormaps all but one window may need to be iconified for the
- colors to be correct. There are a number of tunable parameters to try
- to adjust performance and painting accuracy. The option -8to24
- nogetimage can give a nice speedup if the default depth 24 X server
- supports hiding the 8bpp bits in bits 25-32 of the framebuffer data.
- On very slow machines -8to24 poll=0.2,cachewin=5.0 gives an useful
- speedup. See the -8to24 help description for information on tunable
- parameters, etc.
-
-
- Colors still not working correctly? Run xwininfo on the application
- with the incorrect colors to verify that the depth of its visual is
- different from the default visual depth (gotten from xdpyinfo.) One
- possible workaround in this case is to use the -id option to point
- x11vnc at the application window itself. If the application is
- complicated (lots of toplevel windows and popup menus) this may not be
- acceptable, and may even crash x11vnc (but not the application.) See
- also -appshare.
-
- It is theoretically possible to solve this problem in general (see
- xwd(1) for example), but it does not seem trivial or sufficiently fast
- for x11vnc to be able to do so in real time. The -8to24 method does
- this approximately and is somewhat usable. Fortunately the -overlay
- option works for Solaris machines with overlay visuals where most of
- this problem occurs.
-
-
- Q-25: I am on a high color system (depth >= 24) but I seem to have
- colormap problems. They either flash or everything is very dark.
-
- This can happen if the default Visual (use xdpyinfo to list them) is
- DirectColor instead of TrueColor. These are both usually used in high
- color modes, but whereas TrueColor uses static ramps for the Red,
- Green, and Blue components, DirectColor has arbitrary colormaps for
- the Red, Green, and Blue Components. Currently x11vnc cannot decode
- these colormaps and treats them just like TrueColor.
-
- The only workaround so far is to restart the X server with the "-cc 4"
- option to force TrueColor as the default visual (DirectColor is "-cc
- 5"; see /usr/include/X11/X.h.) The only place we have seen this is
- with the virtual framebuffer server Xvfb on Xorg 7.2. So in that case
- you probably should restart it with something like this: "Xvfb :1 -cc
- 4 -screen 0 1280x1024x24". It should be possible for x11vnc to handle
- DirectColor, but this hasn't been implemented due to its rare usage.
-
- You may also see this problem on an X display with a TrueColor default
- visual where an application chooses a DirectColor visual for its
- window(s). It seems the application also needs to install its own
- colormap for the visual for the colors to be messed up in x11vnc. One
- can make xwud do this for example.
-
-
- Q-26: How do I figure out the window id to supply to the -id windowid
- option?
-
- Run the xwininfo program in a terminal. It will ask you to click on
- the desired application window. After clicking, it will print out much
- information, including the window id (e.g. 0x6000010.) Also, the
- visual and depth of the window printed out is often useful in
- debugging x11vnc color problems.
-
- Also, as of Dec/2004 you can use "-id pick" to have x11vnc run
- xwininfo(1) for you and after you click the window it extracts the
- windowid. Besides "pick" there is also "id:root" to allow you to go
- back to root window when doing remote-control.
-
-
- Q-27: Why don't menus or other transient windows come up when I am
- using the -id windowid option to view a single application window?
-
- This is related to the behavior of the XGetImage(3X11) and
- XShmGetImage() interfaces regarding backingstore, saveunders, etc. The
- way the image is retrieved depends on some aspects of how the X server
- maintains the display image data and whether other windows are
- clipping or obscuring it. See the XGetImage(3X11) man page for more
- details. If you disable BackingStore and SaveUnders in the X server
- you should be able to see these transient windows.
-
- If things are not working and you still want to do the single window
- polling, try the -sid windowid option ("shifted" windowid.)
-
- Update: as of Nov/2009 in the 0.9.9 x11vnc development tarball, there
- is an experimental Application Sharing mode that improves upon the
- -id/-sid single window sharing: -appshare (run "x11vnc -appshare
- -help" for more info.) It is still very primitive and approximate, but
- at least it displays multiple top-level windows.
-
-
- Q-28: My X display is depth 24 at 24bpp (instead of the normal depth
- 24 at 32bpp.) I'm having lots of color and visual problems with x11vnc
- and/or vncviewer. What's up?
-
- First off, depth 24 at 24bpp (bpp=bits-per-pixel) is fairly uncommon
- and can cause problems in general. It also can be slower than depth 24
- at 32bpp. You might want to switch to 32bpp (for XFree86 see the
- "-fbbpp 32", DefaultFbBpp, FbBpp and related options.) Perhaps you
- have 24bpp because the video memory of the machine is low and the
- screen wouldn't fit in video RAM at 32bpp. For this case depth 16 at
- 16bpp might be an acceptable option.
-
- In any event x11vnc should handle depth 24 at 24bpp (although
- performance may be slower, and you may need to use the ZRLE encoding
- instead of Tight.) There are some caveats involving the viewer
- however:
-
- The RealVNC Unix viewer cannot handle 24bpp from the server, it will
- say: "main: setPF: not 8, 16 or 32 bpp?" and exit. I have not checked
- the RealVNC Windows viewer.
-
- So you need to use the TightVNC Unix viewer. However there are some
- problems with that too. It seems libvncserver does not do 24bpp
- correctly with the Tight encoding. The colors and screen ultimately
- get messed up. So you have to use a different encoding with the
- TightVNC vncviewer, try "zlib", "hextile", or one of the other
- encodings (e.g. vncviewer -encodings "zlib hextile" ....) I have not
- checked the TightVNC or UltraVNC Windows viewers.
-
- It appears the older RealVNC Unix viewers (e.g. 3.3.3 and 3.3.7) can
- handle 24bpp from the server, so you may want to use those. They
- evidently request 32 bpp and libvncserver obliges.
-
- Update: as of Apr/2006 you can use the -24to32 option to have x11vnc
- dynamically transform the 24bpp pixel data to 32bpp. This extra
- transformation could slow things down further however.
-
- Now coming the opposite direction if you are running the vncviewer on
- the 24bpp display, TightVNC will fail with "Can't cope with 24
- bits-per-pixel. Sorry." and RealVNC will fail with "main: Error:
- couldn't find suitable pixmap format" so evidently you cannot use
- 24bpp for the vncviewers to work on that X display.
-
- Note, however, that the Unix viewer in the Enhanced TightVNC Viewer
- (SSVNC) project can handle 24bpp X displays. It does this by
- requesting a 16bpp pixel format (or 8bpp if the -bgr233 option has
- been supplied) from the VNC server, and translates that to 24bpp
- locally.
- [Xterminals]
-
- Q-29: Can I use x11vnc to view and interact with an Xterminal (e.g.
- NCD) that is not running UNIX and so x11vnc cannot be run on it
- directly?
-
- You can, but it will likely be very wasteful of network bandwidth
- since you will be polling the X display over the network as opposed to
- over the local hardware. To do this, run x11vnc on a UNIX machine as
- close as possible network-wise (e.g. same switch) to the Xterminal
- machine. Use the -display option to point the display to that of the
- Xterminal (you'll of course need basic X11 permission to do that) and
- finally supply the -noshm option (this enables the polling over the
- network.)
-
- If the Xterminal's X display is open to the network for connections,
- you might use something like "-display xterm123:0". If you are trying
- to do this via an SSH tunnel (assuming you can actually ssh into the
- Xterminal) it will be a little tricky (either use the ssh "-R" option
- or consider ssh-ing in the other direction.) In all cases the X11
- permissions need to allow the connection.
-
- The response will likely be sluggish (maybe only one "frame" per
- second.) This mode is not recommended except for "quick checks" of
- hard to get to X servers. Use something like "-wait 150" to cut down
- on the polling rate. You may also need -flipbyteorder if the colors
- get messed up due to endian byte order differences.
-
- Q-30: How do I get my X permissions (MIT-MAGIC-COOKIE file) correct
- for a Unix/Linux machine acting as an Xterminal?
-
- If the X display machine is a traditional Xterminal (where the X
- server process runs on the Xterminal box, but all of the X client
- applications (firefox, etc) run on a central server (aka "terminal
- server")), you will need to log into the Xterminal machine (i.e. get a
- shell running there) and then start the x11vnc program. If the
- Xterminal Linux/Unix machine is stripped down (e.g. no users besides
- root) that may be difficult.
-
- The next problem is the login Display Manager (e.g. gdm, kdm), and
- hence the MIT-MAGIC-COOKIE auth files, are on the central server and
- not on the Xterminal box where the X server and x11vnc processes are.
-
- So unless X permissions are completely turned off (e.g. "xhost +"), to
- run the x11vnc process on the Xterminal box the MIT-MAGIC-COOKIE auth
- file data (XAUTHORITY or $HOME/.Xauthority) must be accessible by or
- copied to the Xterminal. If $HOME/.Xauthority is exported via NFS
- (this is insecure of course, but has been going on for decades), then
- x11vnc can simply pick it up via NFS (you may need to use the -auth
- option to point to the correct file.) Other options include copying
- the auth file using scp, or something like:
- central-server> xauth nextract - xterm123:0 | ssh xterm123 xauth nmerge -
-
- and then, say, ssh from central-server to xterm123 to start x11vnc.
- Here "xterm123" refers to the computer acting as the Xterminal and
- "central-server" is the terminal server. You can use "xauth -f
- /path/to/cookie-file list" to examine the contents of the cookie(s) in
- a file "/path/to/cookie-file". See the xauth(1) manpage for more
- details.
-
- If the display name in the cookie file needs to be changed between the
- two hosts, see this note on the "xauth add ..." command.
-
- A less secure option is to run something like "xhost +127.0.0.1" while
- sitting at the Xterminal box to allow cookie-free local access for
- x11vnc. You can run "xhost -127.0.0.1" after x11vnc connects if you
- want to go back to the original permissions.
-
- If the Xterminal is really stripped down and doesn't have any user
- accounts, NFS, etc. you'll need to contact your system administrator
- to set something up. It can be done!!! Some Xterminal projects have
- actually enabled "run locally" facilities for the running of an
- occasional app more efficiently locally on the Xterminal box (e.g.
- realplayer.)
-
- Not recommended, but as a last resort, you could have x11vnc poll the
- Xterminal Display over the network. For this you would run a "x11vnc
- -noshm ..." process on the central-server (and hope the network admin
- doesn't get angry...)
-
- Note: use of Display Manager (gdm, kdm, ...) auth cookie files (i.e.
- from /var/..., /tmp/..., or elsewhere) may require modification via
- xauth(1) to correctly include the display x11vnc refers to (e.g.
- "xauth -f cookie-file add :0 . 45be51ae2ce9dfbacd882ab3ef8e96b1",
- where the "45be51..." cookie value was found from an "xauth -f
- /path/to/original/cookie-file list") or other reasons. See xauth(1)
- manpage for full details on how to transfer an MIT-MAGIC-COOKIE
- between machines and displays.
-
- VNCviewer performance on Xterminals: This isn't related to x11vnc on
- Xterminals, but we mention it here anyway because of the similar
- issues. If you are on an Xterminal and want to use vncviewer to
- connect to a VNC server somewhere, then performance would be best if
- you ran the viewer on the Xterminal box. Otherwise, (i.e. running the
- viewer process on the central-server) all of the vncviewer screen
- drawing is done more inefficiently over the network. Something to
- consider, especially on a busy network. (BTW, this has all of the
- above permission, etc, problems: both vncviewer and x11vnc are X
- client apps desired to be run on the Xterminal box.)
-
- [Sun Rays]
-
- Q-31: I'm having trouble using x11vnc with my Sun Ray session.
-
- The Sun Ray technology is a bit like "VNC done in hardware" (the Sun
- Ray terminal device, DTU, playing the role of the vncviewer.)
- Completely independent of that, the SunRay user's session is still an
- X server that speaks the X11 protocol and so x11vnc simply talks to
- the X server part to export the SunRay desktop to any place in the
- world (i.e. not only to a Sun Ray terminal device), creating a sort of
- "Soft Ray". Please see this discussion of Sun Ray issues for solutions
- to problems.
-
- Also see the Sun Ray Remote Control Toolkit that uses x11vnc.
-
- [Remote Control]
-
- Q-32: How do I stop x11vnc once it is running in the background?
-
- As of Dec/2004 there is a remote control feature. It can change a huge
- number of parameters on the fly: see the -remote and -query options.
- To shut down the running x11vnc server just type "x11vnc -R stop". To
- disconnect all clients do "x11vnc -R disconnect:all", etc.
-
- If the -forever option has not been supplied, x11vnc will
- automatically exit after the first client disconnects. In general if
- you cannot use the remote control, then you will have to kill the
- x11vnc process This can be done via: "kill NNNNN" (where NNNNN is the
- x11vnc process id number found from ps(1)), or "pkill x11vnc", or
- "killall x11vnc" (Linux only.)
-
- If you have not put x11vnc in the background via the -bg option or
- shell & operator, then simply press Ctrl-C in the shell where x11vnc
- is running to stop it.
-
- Potential Gotcha: If somehow your Keypress of Ctrl-C went through
- x11vnc to the Xserver that then delivered it to x11vnc it is possible
- one or both of the Ctrl or C keys will be left stuck in the pressed
- down state in the Xserver. Tapping the stuck key (either via a new
- x11vnc or at the physical console) will release it from the stuck
- state. If the keyboard seems to be acting strangely it is often fixed
- by tapping Ctrl, Shift, and Alt. Alternatively, the -clear_mods option
- and -clear_keys option can be used to release pressed keys at startup
- and exit. The option -clear_all will also try to unset Caps_Lock,
- Num_Lock, etc.
-
-
- Q-33: Can I change settings in x11vnc without having to restart it?
- Can I remote control it?
-
- Look at the -remote (an alias is -R) and -query (an alias is -Q)
- options added in Dec/2004. They allow nearly everything to be changed
- dynamically and settings to be queried. Examples: "x11vnc -R shared",
- "x11vnc -R forever", "x11vnc -R scale:3/4", "x11vnc -Q modtweak",
- "x11vnc -R stop", "x11vnc -R disconnect:all", etc..
-
- These commands do not start a x11vnc server, but rather communicate
- with one that is already running. The X display (X11VNC_REMOTE
- property) is used as the communication channel, so the X permissions
- and DISPLAY must be set up correctly for communication to be possible.
-
- There is also a simple Tcl/Tk gui based on this remote control
- mechanism. See the -gui option for more info. You will need to have
- Tcl/Tk (i.e. /usr/bin/wish) installed for it to work. It can also run
- in the system tray: "-gui tray" or as a standalone small icon window:
- "-gui icon". Use "-gui tray=setpass" for a naive user "Share My
- Desktop" mode.
-
- [Security and Permissions]
-
- Q-34: How do I create a VNC password for use with x11vnc?
-
- You may already have one in $HOME/.vnc/passwd if you have used, say,
- the vncserver program from the regular RealVNC or TightVNC packages
- (i.e. launching the Xvnc server.) Otherwise, you could use the
- vncpasswd(1) program from those packages.
-
- As of Jun/2004 x11vnc supports the -storepasswd "pass" "file" option,
- which is the same functionality of storepasswd. Be sure to quote the
- "pass" if it contains shell meta characters, spaces, etc. Example:
- x11vnc -storepasswd 'sword*fish' $HOME/myvncpasswd
-
- You then use the password via the x11vnc option: "-rfbauth
- $HOME/myvncpasswd"
-
- As of Jan/2006 if you do not supply any arguments:
- x11vnc -storepasswd
-
- you will be prompted for a password to save to ~/.vnc/passwd (your
- keystrokes when entering the password will not be echoed to the
- screen.) If you supply one argument, e.g. "x11vnc -storepasswd
- ~/.mypass", the password you are prompted for will be stored in that
- file.
-
- x11vnc also has the -passwdfile and -passwd/-viewpasswd plain text
- (i.e. not obscured like the -rfbauth VNC passwords) password options.
-
- You can use the -usepw option to automatically use any password file
- you have in ~/.vnc/passwd or ~/.vnc/passwdfile (the latter is used
- with the -passwdfile option.)
-
- x11vnc -usepw -display :0 ...
-
- If neither file exists you are prompted to store a password in
- ~/.vnc/passwd. If a password file cannot be found or created x11vnc
- exits immediately. An admin may want to set it up this way for users
- who do not know better.
-
-
- Q-35: Can I make it so -storepasswd doesn't show my password on the
- screen?
-
- You can use the vncpasswd program from RealVNC or TightVNC mentioned
- above. As of Jan/2006 the -storepasswd option without any arguments
- will not echo your password as you type it and save the file to
- ~/.vnc/passwd:
- # x11vnc -storepasswd
- Enter VNC password:
- Verify password:
- Write password to /home/myname/.vnc/passwd? [y]/n
- Password written to: /home/myname/.vnc/passwd
-
- You can also give it an alternate filename, e.g. "x11vnc -storepasswd
- ~/.mypass"
-
-
- Q-36: Can I have two passwords for VNC viewers, one for full access
- and the other for view-only access to the display?
-
- Yes, as of May/2004 there is the -viewpasswd option to supply the
- view-only password. Note the full-access password option -passwd must
- be supplied at the same time. E.g.: -passwd sword -viewpasswd fish.
-
- To avoid specifying the passwords on the command line (where they
- could be observed via the ps(1) command by any user) you can use the
- -passwdfile option to specify a file containing plain text passwords.
- Presumably this file is readable only by you, and ideally it is
- located on the machine x11vnc is run on (to avoid being snooped on
- over the network.) The first line of this file is the full-access
- password. If there is a second line in the file and it is non-blank,
- it is taken as the view-only password. (use "__EMPTY__" to supply an
- empty one.)
-
- View-only passwords currently do not work for the -rfbauth password
- option (standard VNC password storing mechanism.) FWIW, note that
- although the output (usually placed in $HOME/.vnc/passwd) by the
- vncpasswd or storepasswd programs (or from x11vnc -storepasswd) looks
- encrypted they are really just obscured to avoid "casual" password
- stealing. It takes almost no skill to figure out how to extract the
- plain text passwords from $HOME/.vnc/passwd since it is very
- straight-forward to work out what to do from the VNC source code.
-
-
- Q-37: Can I have as many full-access and view-only passwords as I
- like?
-
- Yes, as of Jan/2006 in the libvncserver CVS the -passwdfile option has
- been extended to handle as many passwords as you like. You put the
- view-only passwords after a line __BEGIN_VIEWONLY__.
-
- You can also easily annotate and comment out passwords in the file.
- You can have x11vnc re-read the file dynamically when it is modified.
-
-
- Q-38: Does x11vnc support Unix usernames and passwords? Can I further
- limit the set of Unix usernames who can connect to the VNC desktop?
- Update: as of Feb/2006 x11vnc has the -unixpw option that does this
- outside of the VNC protocol and libvncserver. The standard su(1)
- program is used to validate the user's password. A familiar "login:"
- and "Password:" dialog is presented to the user on a black screen
- inside the vncviewer. The connection is dropped if the user fails to
- supply the correct password in 3 tries or does not send one before a
- 25 second timeout. Existing clients are view-only during this period.
- A list of allowed Unix usernames may also be supplied along with
- per-user settings.
-
- There is also the -unixpw_nis option for non-shadow-password
- (typically NIS environments, hence the name) systems where the
- traditional getpwnam() and crypt() functions are used instead of
- su(1). The encrypted user passwords must be accessible to the user
- running x11vnc in -unixpw_nis mode, otherwise the logins will always
- fail even when the correct password is supplied. See ypcat(1) and
- shadow(5).
-
- Two settings are enforced in the -unixpw and -unixpw_nis modes to
- provide extra security: the 1) -localhost and 2) -stunnel or -ssl
- options. Without these one might send the Unix username and password
- data in clear text over the network which is a very bad idea. They can
- be relaxed if you want to provide encryption other than stunnel or
- -ssl (the constraint is automatically relaxed if SSH_CONNECTION is set
- and indicates you have ssh-ed in, however the -localhost requirement
- is still enforced.)
-
- The two -unixpw modes have been tested on Linux, Solaris, Mac OS X,
- HP-UX, AIX, Tru64, FreeBSD, OpenBSD, and NetBSD. Additional testing is
- appreciated. For the last 4 it appears that su(1) will not prompt for
- a password if su-ing to oneself. Since x11vnc requires a password
- prompt from su, x11vnc forces those logins to fail even when the
- correct password is supplied. On *BSD it appears this can be corrected
- by removing the pam_self.so entry in /etc/pam.d/su.
-
-
- Previous older discussion (prior to the -unixpw option):
-
- Until the VNC protocol and libvncserver support this things will be
- approximate at best.
-
- One approximate method involves starting x11vnc with the -localhost
- option. This basically requires the viewer user to log into the
- workstation where x11vnc is running via their Unix username and
- password, and then somehow set up a port redirection of his vncviewer
- connection to make it appear to emanate from the local machine. As
- discussed above, ssh is useful for this: "ssh -L 5900:localhost:5900
- user@hostname ..." See the ssh wrapper scripts mentioned elsewhere on
- this page. stunnel does this as well.
-
- Of course a malicious user could allow other users to get in through
- his channel, but that is a problem with every method. Another thing to
- watch out for is a malicious user on the viewer side (where ssh is
- running) trying to sneak in through the ssh port redirection there.
-
- Regarding limiting the set of Unix usernames who can connect, the
- traditional way would be to further require a VNC password to supplied
- (-rfbauth, -passwd, etc) and only tell the people allowed in what the
- VNC password is. A scheme that avoids a second password involves using
- the -accept option that runs a program to examine the connection
- information to determine which user is connecting from the local
- machine. That may be difficult to do, but, for example, the program
- could use the ident service on the local machine (normally ident
- should not be trusted over the network, but on the local machine it
- should be accurate: otherwise root has been compromised and so there
- are more serious problems! Unfortunately recent Linux distros seem to
- provide a random string (MD5 hash?) instead of the username.) An
- example script passed in via -accept scriptname that deduces the Unix
- username and limits who can be accepted might look something like
- this:
-#!/bin/sh
-if [ "$RFB_CLIENT_IP" != "127.0.0.1" -o "$RFB_SERVER_IP" != "127.0.0.1" ]; then
- exit 1 # something fishy... reject it.
-fi
-user=`echo "$RFB_CLIENT_PORT, $RFB_SERVER_PORT" | nc -w 1 $RFB_CLIENT_IP 113 \
- | grep 'USERID.*UNIX' | head -n 1 | sed -e 's/[\r ]//g' | awk -F: '{pri
-nt $4}'`
-
-for okuser in fred barney wilma betty
-do
- if [ "X$user" = "X$okuser" ]; then
- exit 0 # accept it
- fi
-done
-exit 1 # reject it
-
- For this to work with ssh port redirection, the ssh option
- UsePrivilegeSeparation must be enabled otherwise the userid will
- always be "root".
-
- Here is a similar example based on Linux netstat(1) output:
-#!/bin/sh
-#
-# accept_local_netstat: x11vnc -accept command to accept a local
-# vncviewer connection from acceptable users. Linux netstat -nte is used.
-
-PATH=/bin:/usr/bin:$PATH; export PATH; # set to get system utils
-
-allowed="`id -u fred`"; # add more user numbers if desired.
-
-# check required settings
-ok=1
-if [ "X$allowed" = "X" ]; then
- ok=0; # something wrong with allowed list
-fi
-if [ "X$RFB_CLIENT_IP" != "X127.0.0.1" -o "X$RFB_SERVER_IP" != "X127.0.0.1" ];
-then
- ok=0; # connection not over localhost
-fi
-if [ "$RFB_CLIENT_PORT" -le 0 -o "$RFB_SERVER_PORT" -le 0 ]; then
- ok=0; # something wrong with tcp port numbers
-fi
-if [ "$ok" = 0 ]; then
- echo "$0: invalid setting:" 1>&2
- env | grep ^RFB | sort 1>&2
- exit 1
-fi
-
-# Linux netstat -nte:
-# Proto Recv-Q Send-Q Local Address Foreign Address State
- User Inode
-# 0 0 0 RFB_CLIENT RFB_SERVER ESTABLISHED
- nnnn ....
-#
-user=`netstat -nte | grep ESTABLISHED \
- | grep " $RFB_CLIENT_IP:$RFB_CLIENT_PORT *$RFB_SERVER_IP:$RFB_SERVER_P
-ORT "`
-
-echo "netstat match: $user" 1>&2
-user=`echo "$user" | head -n 1 | sed -e 's/^.*ESTABLISHED/ /' | awk '{print $1}
-'`
-
-ok=0
-for u in $allowed
-do
- if [ "X$user" = "X$u" ]; then
- ok=1
- break
- fi
-done
-
-if [ "X$ok" = "X1" ]; then
- echo "$0: user accepted: '$user'" 1>&2
- exit 0
-else
- echo "$0: user '$user' invalid:" 1>&2
- echo "$0: allowed: $allowed" 1>&2
- env | grep ^RFB | sort 1>&2
- exit 1
-fi
-
-
- Q-39: Can I supply an external program to provide my own custom login
- method (e.g. Dynamic/One-time passwords or non-Unix (LDAP) usernames
- and passwords)?
- Yes, there are several possibilities. For background see the FAQ on
- the -accept where an external program may be run to decide if a VNC
- client should be allowed to try to connect and log in. If the program
- (or local user prompted by a popup) answers "yes", then -accept
- proceeds to the normal VNC and x11vnc authentication methods,
- otherwise the connection is dropped.
-
- To provide more direct coupling to the VNC client's username and/or
- supplied password the following options were added in Sep/2006:
- * -unixpw_cmd command
- * -passwdfile cmd:command
- * -passwdfile custom:command
-
- In each case "command" is an external command run by x11vnc. You
- supply it. For example, it may couple to your LDAP system or other
- servers you set up.
-
- For -unixpw_cmd the normal -unixpw Login: and Password: prompts are
- supplied to the VNC viewer and the strings the client returns are then
- piped into "command" as the first two lines of its standard input. If
- the command returns success, i.e. exit(0), the VNC client is accepted,
- otherwise it is rejected.
-
- For "-passwdfile cmd:command" the command is run and it returns a
- password list (like a password file, see the -passwdfile read:filename
- mode.) Perhaps a dynamic, one-time password is retrieved from a server
- this way.
-
- For "-passwdfile custom:command" one gets complete control over the
- VNC challenge-response dialog with the VNC client. x11vnc sends out a
- string of random bytes (16 by the VNC spec) and the client returns the
- same number of bytes in a way the server can verify only the
- authorized user could have created. The VNC protocol specifies DES
- encryption with a password. If you are willing to modify the VNC
- viewers, you can have it be anything you want, perhaps a less
- crackable MD5 hash scheme or one-time pad. Your program will read from
- its standard input the size of the challenge-response followed by a
- newline, then the challenge bytes followed by the response bytes. If
- your command then returns success, i.e. exit(0), the VNC client is
- accepted, otherwise it is rejected.
-
- In all cases the "RFB_*" environment variables are set as under
- -accept. These variables can provide useful information for the
- externally supplied program to use.
-
-
- Q-40: Why does x11vnc exit as soon as the VNC viewer disconnects? And
- why doesn't it allow more than one VNC viewer to connect at the same
- time?
-
- These defaults are simple safety measures to avoid someone unknowingly
- leaving his X11 desktop exposed (to the internet, say) for long
- periods of time. Use the -forever option (aka -many) to have x11vnc
- wait for more connections after the first client disconnects. Use the
- -shared option to have x11vnc allow multiple clients to connect
- simultaneously.
-
- Recommended additional safety measures include using ssh (see above),
- stunnel, -ssl, or a VPN to authenticate and encrypt the viewer
- connections or to at least use the -rfbauth passwd-file option to use
- VNC password protection (or -passwdfile) It is up to YOU to apply
- these security measures, they will not be done for you automatically.
-
-
- Q-41: Can I limit which machines incoming VNC clients can connect
- from?
-
- Yes, look at the -allow and -localhost options to limit connections by
- hostname or IP address. E.g.
- x11vnc -allow 192.168.0.1,192.168.0.2
-
- for those two hosts or
- x11vnc -allow 192.168.0.
-
- for a subnet. For individual hosts you can use the hostname instead of
- the IP number, e.g.: "-allow snoopy", and "-allow darkstar,wombat".
- Note that -localhost achieves the same thing as "-allow 127.0.0.1"
-
- For more control, build libvncserver with libwrap support
- (tcp_wrappers) and then use /etc/hosts.allow See hosts_access(5) for
- complete details.
-
-
- Q-42: How do I build x11vnc/libvncserver with libwrap (tcp_wrappers)
- support?
-
- Here is one way to pass this information to the configure script:
- env CPPFLAGS=-DUSE_LIBWRAP LDFLAGS=-lwrap ./configure
-
- then run make as usual. This requires libwrap and its development
- package (tcpd.h) to be installed on the build machine. If additional
- CPPFLAGS or LDFLAGS options are needed supply them as well using
- quotes.
-
- The resulting x11vnc then uses libwrap/tcp_wrappers for connections.
- The service name you will use in /etc/hosts.allow and /etc/hosts.deny
- is "vnc", e.g.:
- vnc: 192.168.100.3 .example.com
-
- Note that if you run x11vnc out of inetd you do not need to build
- x11vnc with libwrap support because the /usr/sbin/tcpd reference in
- /etc/inetd.conf handles the tcp_wrappers stuff.
-
-
- Q-43: Can I have x11vnc only listen on one network interface (e.g.
- internal LAN) rather than having it listen on all network interfaces
- and relying on -allow to filter unwanted connections out?
-
- As of Mar/2005 there is the "-listen ipaddr" option that enables this.
- For ipaddr either supply the desired network interface's IP address
- (or use a hostname that resolves to it) or use the string "localhost".
- For additional filtering simultaneously use the "-allow host1,..."
- option to allow only specific hosts in.
-
- This option is useful if you want to insure that no one can even begin
- a dialog with x11vnc from untrusted network interfaces (e.g. ppp0.)
- The option -localhost now implies "-listen localhost" since that is
- what most people expect it to do.
-
-
- Q-44: Now that -localhost implies listening only on the loopback
- interface, how I can occasionally allow in a non-localhost via the -R
- allowonce remote control command?
-
- To do this specify "-allow localhost". Unlike -localhost this will
- leave x11vnc listening on all interfaces (but of course only allowing
- in local connections, e.g. ssh redirs.) Then you can later run "x11vnc
- -R allowonce:somehost" or use to gui to permit a one-shot connection
- from a remote host.
-
-
- Q-45: Can I fine tune what types of user input are allowed? E.g. have
- some users just be able to move the mouse, but not click or type
- anything?
-
- As of Feb/2005, the -input option allows you to do this. "K", "M",
- "B", "C", and "F" stand for Keystroke, Mouse-motion, Button-clicks,
- Clipboard, and File-Transfer, respectively. The setting: "-input M"
- makes attached viewers only able to move the mouse. "-input KMBC,M"
- lets normal clients do everything and enables view-only clients to
- move the mouse.
-
- These settings can also be applied on a per-viewer basis via the
- remote control mechanism or the GUI. E.g. x11vnc -R input:hostname:M
-
-
- Q-46: Can I prompt the user at the local X display whether the
- incoming VNC client should be accepted or not? Can I decide to make
- some clients view-only? How about running an arbitrary program to make
- the decisions?
-
- Yes, look at the "-accept command" option, it allows you to specify an
- external command that is run for each new client. (use quotes around
- the command if it contains spaces, etc.) If the external command
- returns 0 (success) the client is accepted, otherwise with any other
- return code the client is rejected. See below how to also accept
- clients view-only.
-
- The external command will have the RFB_CLIENT_IP environment variable
- set to the client's numerical IP address, RFB_CLIENT_PORT its port
- number. Similarly for RFB_SERVER_IP and RFB_SERVER_PORT to allow
- identification of the tcp virtual circuit. DISPLAY will be set to that
- of the X11 display being polled. Also, RFB_X11VNC_PID is set to the
- x11vnc process id (e.g. in case you decided to kill it), RFB_CLIENT_ID
- will be an id number, and RFB_CLIENT_COUNT the number of other clients
- currently connected. RFB_MODE will be "accept".
-
- Built-in Popup Window: As a special case, "-accept popup" will
- instruct x11vnc to create its own simple popup window. To accept the
- client press "y" or click mouse on the "Yes" button. To reject the
- client press "n" or click mouse on the "No" button. To accept the
- client View-only, press "v" or click mouse on the "View" button. If
- the -viewonly option has been supplied, the "View" action will not be
- present: the whole display is view only in that case.
-
- The popup window times out after 120 seconds, to change this behavior
- use "-accept popup:N" where N is the number of seconds (use 0 for no
- timeout.) More tricks: "-accept popupmouse" will only take mouse click
- responses, while "-accept popupkey" will only take keystroke responses
- (popup takes both.) After any of the 3 popup keywords you can supply a
- position of the window: +N+M, (the default is to center the window)
- e.g. -accept popupmouse+10+10.
-
- Also as a special case "-accept xmessage" will run the xmessage(1)
- program to prompt the user whether the client should be accepted or
- not. This requires that you have xmessage installed and available via
- PATH. In case it is not already on your system, the xmessage program
- is available at ftp://ftp.x.org/
- (End of Built-in Popup Window:)
-
- To include view-only decisions for the external commands, prefix the
- command something like this: "yes:0,no:*,view:3 mycommand ..." This
- associates the three actions: yes(accept), no(reject), and
- view(accept-view-only), with the numerical return (i.e. exit()) codes.
- Use "*" instead of a number to set the default action (e.g. in case
- the external command returns an unexpected return code.)
-
- Here is an example -accept script called accept_or_lock. It uses
- xmessage and xlock (replace with your screen lock command, maybe it is
- "xscreensaver-command -lock", or kdesktop_lock, or "dtaction
- LockDisplay".) It will prompt the user at the X display whether to
- accept, reject, or accept view-only the client, but if the prompt
- times out after 60 seconds the screen is locked and the VNC client is
- accepted. This allows the remote access when no one is at the display.
-#!/bin/sh
-#
-# accept_or_lock: prompt user at X display whether to accept an incoming
-# VNC connection. If timeout expires, screen is locked
-# and the VNC viewer is accepted (allows remote access
-# when no one is sitting at the display.)
-#
-# usage: x11vnc ... -forever -accept 'yes:0,no:*,view:4 accept_or_lock'
-#
-xmessage -buttons yes:2,no:3,view-only:4 -center \
- -timeout 60 "x11vnc: accept connection from $RFB_CLIENT_IP?"
-rc=$?
-if [ $rc = 0 ]; then
- xlock & # or "xlock -mode blank" for no animations.
- sleep 5
- exit 0
-elif [ $rc = 2 ]; then
- exit 0
-elif [ $rc = 4 ]; then
- exit 4
-fi
-exit 1
-
- Stefan Radman has written a nice dtksh script dtVncPopup for use in
- CDE environments to do the same sort of thing. Information on how to
- use it is found at the top of the file. He encourages you to provide
- feedback to him to help improve the script.
-
- Note that in all cases x11vnc will block while the external command or
- popup is being run, so attached clients will not receive screen
- updates, etc during this period.
-
- To run a command when a client disconnects, use the "-gone command"
- option. This is for the user's convenience only: the return code of
- the command is not interpreted by x11vnc. The same environment
- variables are set as in "-accept command" (except that RFB_MODE will
- be "gone".)
-
- As of Jan/2006 the "-afteraccept command" option will run the command
- only after the VNC client has been accepted and authenticated. Like
- -gone the return code is not interpreted. RFB_MODE will be
- "afteraccept".)
-
-
- Q-47: I start x11vnc as root because it is launched via inetd(8) or a
- display manager like gdm(1). Can I have x11vnc later switch to a
- different user?
-
- As of Feb/2005 x11vnc has the -users option that allows things like
- this. Please read the documentation on it (also in the x11vnc -help
- output) carefully for features and caveats. It's use can often
- decrease security unless care is taken.
-
- BTW, a nice use of it is "-users +nobody" that switches to the Unix
- user nobody right after connections to the X display are established.
-
- In any event, while running x11vnc as root, remember it comes with no
- warranty ;-).
-
-
- Q-48: I use a screen-lock when I leave my workstation (e.g.
- xscreensaver or xlock.) When I remotely access my workstation desktop
- via x11vnc I can unlock the desktop fine, but I am worried people will
- see my activities on the physical monitor. What can I do to prevent
- this, or at least make it more difficult?
-
- Probably most work environments would respect your privacy if you
- powered off the monitor. Also remember if people have physical access
- to your workstation they basically can do anything they want with it
- (e.g. install a backdoor for later use, etc.)
-
- In any event, as of Jun/2004 there is an experimental utility to make
- it more difficult for nosey people to see your x11vnc activities. The
- source for it is blockdpy.c The idea behind it is simple (but
- obviously not bulletproof): when a VNC client attaches to x11vnc put
- the display monitor in the DPMS "off" state, if the DPMS state ever
- changes immediately start up the screen-lock program. The x11vnc user
- will notice something is happening and think about what to do next
- (while the screen is in a locked state.)
-
- This works (or at least has a chance of working) because if the
- intruder moves the mouse or presses a key on the keyboard, the monitor
- wakes up out of the DPMS off state, and this induces the screen lock
- program to activate as soon as possible. Of course there are cracks in
- this, the eavesdropper could detach your monitor and insert a non-DPMS
- one, and there are race conditions. As mentioned above this is not
- bulletproof. A really robust solution would likely require X server
- and perhaps even video hardware support.
-
- The blockdpy utility is launched by the -accept option and told to
- exit via the -gone option (the vnc client user should obviously
- re-lock the screen before disconnecting!) Instructions can be found in
- the source code for the utility at the above link. Roughly it is
- something like this:
- x11vnc ... -accept "blockdpy -bg -f $HOME/.bdpy" -gone "touch $HOME/.bdpy"
-
- but please read the top of the file.
-
- Update: As of Feb/2007 there is some builtin support for this:
- -forcedpms and -clientdpms however, they are probably less robust than
- the above blockdpy.c scheme, since if the person floods the physical
- machine with mouse or pointer input he can usually see flashes of the
- screen before the monitor is powered off again. See also the -grabkbd,
- -grabptr, and -grabalways options.
-
-
- Q-49: Can I have x11vnc automatically lock the screen when I
- disconnect the VNC viewer?
-
- Yes, a user mentions he uses the -gone option under CDE to run a
- screen lock program:
- x11vnc -display :0 -forever -gone 'dtaction LockDisplay'
-
- Other possibilities are:
- x11vnc -display :0 -forever -gone 'xscreensaver-command -lock'
- x11vnc -display :0 -forever -gone 'kdesktop_lock'
- x11vnc -display :0 -forever -gone 'xlock &'
- x11vnc -display :0 -forever -gone 'xlock -mode blank &'
-
- Here is a scheme using the -afteraccept option (in version 0.8) to
- unlock the screen after the first valid VNC login and to lock the
- screen after the last valid VNC login disconnects:
- x11vnc -display :0 -forever -shared -afteraccept ./myxlocker -gone ./myxlocke
-r
-
- Where the script ./myxlocker is:
-#!/bin/sh
-
-#/usr/bin/env | grep RFB_ | sort # for viewing RFB_* settings.
-
-if [ "X$RFB_MODE" = "Xafteraccept" ]; then
- if [ "X$RFB_STATE" = "XNORMAL" ]; then # require valid login
- if [ "X$RFB_CLIENT_COUNT" = "X1" ]; then
- killall xlock # Linux only.
- fi
- fi
-elif [ "X$RFB_MODE" = "Xgone" ]; then
- if [ "X$RFB_STATE" = "XNORMAL" ]; then # require valid login
- if [ "X$RFB_CLIENT_COUNT" = "X0" ]; then
- xlock -mode blank &
- fi
- fi
-fi
-
- Note the xlock option "-mode blank" to avoid animations.
-
- There is a problem if you have x11vnc running this way in -forever
- mode and you hit Ctrl-C to stop it. The xlock (or other program) will
- get killed too. To work around this make a little script called
- setpgrp that looks like:
-#!/usr/bin/perl
-setpgrp(0, 0);
-exec @ARGV;
-
- then use -gone "setpgrp xlock &", etc.
- [Encrypted Connections]
-
- Q-50: How can I tunnel my connection to x11vnc via an encrypted SSH
- channel between two Unix machines?
-
- See the description earlier on this page on how to tunnel VNC via SSH
- from Unix to Unix. A number of ways are described along with some
- issues you may encounter.
-
- Other secure encrypted methods exists, e.g. stunnel, IPSEC, various
- VPNs, etc.
-
- See also the Enhanced TightVNC Viewer (SSVNC) page where much of this
- is now automated.
-
-
- Q-51: How can I tunnel my connection to x11vnc via an encrypted SSH
- channel from Windows using an SSH client like Putty?
-
- Above we described how to tunnel VNC via SSH from Unix to Unix, you
- may want to review it. To do this from Windows using Putty it would go
- something like this:
- * In the Putty dialog window under 'Session' enter the hostname or
- IP number of the Unix machine with display to be viewed.
- * Make sure the SSH protocol is selected and the server port is
- correct.
- * Under 'Connections/SSH/Tunnels' Add a Local connection with
- 'Source port: 5900' and 'Destination: localhost:5900'
- * Log into the remote machine by pressing 'Open' and supplying
- username, password, etc.
- * In that SSH shell, start up x11vnc by typing the command: x11vnc
- -display :0 plus any other desired options (e.g. -localhost.)
- * Finally, start up your VNC Viewer in Windows and enter
- 'localhost:0' as the VNC server.
-
- You can keep all of the settings in a Putty 'Saved Session'. Also,
- once everything is working, you can consider putting x11vnc -display
- :0 (plus other cmdline options) in the 'Remote command' Putty setting
- under 'Connections/SSH'.
-
- See also the Enhanced TightVNC Viewer (SSVNC) page where much of this
- is now automated via the Putty plink utility.
-
- For extra protection feel free to run x11vnc with the -localhost and
- -rfbauth/-passwdfile options.
-
- If the machine you SSH into via Putty is not the same machine with the
- X display you wish to view (e.g. your company provides incoming SSH
- access to a gateway machine), then you need to change the above Putty
- dialog setting to: 'Destination: otherhost:5900', Once logged in,
- you'll need to do a second login (ssh or rsh) to the workstation
- machine 'otherhost' and then start up x11vnc on it. This can also be
- automated by Chaining SSH's.
-
- As discussed above another option is to first start the VNC viewer in
- "listen" mode, and then launch x11vnc with the "-connect localhost"
- option to establish the reverse connection. In this case a Remote port
- redirection (not Local) is needed for port 5500 instead of 5900 (i.e.
- 'Source port: 5500' and 'Destination: localhost:5500' for a Remote
- connection.)
-
-
- Q-52: How can I tunnel my connection to x11vnc via an encrypted SSL
- channel using an external tool like stunnel?
-
- It is possible to use a "lighter weight" encryption setup than SSH or
- IPSEC. SSL tunnels such as stunnel (also stunnel.org) provide an
- encrypted channel without the need for Unix users, passwords, and key
- passphrases required for ssh (and at the other extreme SSL can also
- provide a complete signed certificate chain of trust.) On the other
- hand, since SSH is usually installed everywhere and firewalls often
- let its port through, ssh is frequently the path of least resistance
- (it also nicely manages public keys for you.)
-
- Update: As of Feb/2006 x11vnc has the options -ssl, -stunnel, and
- -sslverify to provide integrated SSL schemes. They are discussed in
- the Next FAQ (you probably want to skip to it now.)
-
- We include these non-built-in method descriptions below for historical
- reference. They are handy because can be used to create SSL tunnels to
- any VNC (or other type of) server.
-
-
- Here are some basic examples using stunnel but the general idea for
- any SSL tunnel utility is the same:
- * Start up x11vnc and constrain it to listen on localhost.
- * Then start up the SSL tunnel running on the same machine to
- forward incoming connections to that x11vnc.
- * Set up and run a similar SSL tunnel for the outgoing connection on
- the VNC viewer machine pointing it to the SSL/x11vnc server.
- * Optionally, set up server (or even client) public/private keys for
- use in authenticating one side to the other.
- * Finally, start the VNC Viewer and tell it to connect to the local
- port (e.g. a vnc display localhost:0) where its outgoing SSL
- tunnel is listening.
-
- We'll first use the stunnel version 3 syntax since it is the most
- concise and Unixy.
-
- Start up x11vnc listening on port 5900:
- x11vnc -display :0 -rfbport 5900 -localhost -bg -passwdfile ~/mypass
-
- Then start stunnel (version 3, not 4) with this command:
- stunnel -d 5901 -r 5900 -p /path/to/stunnel.pem
-
- The above two commands are run on host "far-away.east". The
- stunnel.pem is the self-signed PEM file certificate created when
- stunnel is built. One can also create certificates signed by
- Certificate Authorities or self-signed if desired using the x11vnc
- utilities described there.
-
- SSL Viewers: Next, on the VNC viewer side we need an SSL tunnel to
- encrypt the outgoing connection. The nice thing is any SSL tunnel can
- be used because the protocol is a standard. For this example we'll
- also use stunnel on the viewer side on Unix. First start up the
- client-side stunnel (version 3, not 4):
- stunnel -c -d localhost:5902 -r far-away.east:5901
-
- Then point the viewer to the local tunnel on port 5902:
- vncviewer -encodings "copyrect tight zrle hextile" localhost:2
-
- That's it. Note that the ss_vncviewer script can automate this
- easily, and so can the Enhanced TightVNC Viewer (SSVNC) package.
-
- Be sure to use a VNC password because unlike ssh by default the
- encrypted SSL channel provides no authentication (only privacy.) With
- some extra configuration one could also set up certificates to provide
- authentication of either or both sides as well (and hence avoid
- man-in-the-middle attacks.) See the stunnel and openssl documentation
- and also the key management section for details.
-
- stunnel has also been ported to Windows, and there are likely others
- to choose from for that OS. Much info for using it on Windows can be
- found at the stunnel site and in this article The article also shows
- the detailed steps to set up all the authentication certificates. (for
- both server and clients, see also the x11vnc utilities that do this.)
- The default Windows client setup (no certs) is simpler and only 4
- files are needed in a folder: stunnel.exe, stunnel.conf, libssl32.dll,
- libeay32.dll. We used an stunnel.conf containing:
-# stunnel.conf:
-client = yes
-options = ALL
-[myvncssl]
-accept = localhost:5902
-connect = far-away.east:5901
-
- then double click on the stunnel.exe icon to launch it (followed by
- pointing the VNC viewer to localhost:2).
-
-
- stunnel inetd-like mode:
-
- As an aside, if you don't like the little "gap" of unencrypted TCP
- traffic (and a localhost listening socket) on the local machine
- between stunnel and x11vnc it can actually be closed by having stunnel
- start up x11vnc in -inetd mode:
- stunnel -p /path/to/stunnel.pem -P none -d 5900 -l ./x11vnc_sh
-
- Where the script x11vnc_sh starts up x11vnc:
-#!/bin/sh
-x11vnc -q -inetd -display :0 -passwdfile ~/mypass
-
- Note that this creates a separate x11vnc process for each incoming
- connection (as any inetd x11vnc usage would), but for the case of
- normally just one viewer at a time it should not be a big problem.
-
-
- stunnel 4 syntax:
-
- Somewhat sadly, the stunnel version 4 syntax is not so amenable to the
- command line or scripts. You need to create a config file with the
- parameters. E.g.:
- stunnel x11vnc.cfg
-
- Where the file x11vnc.cfg contains:
-foreground = yes
-pid =
-cert = /path/to/stunnel.pem
-[x11vnc_stunnel]
-accept = 5901
-connect = 5900
-
- One nice thing about version 4 is often the PEM file does not need to
- be specified because stunnel finds it in its installed area. One other
- gotcha the PEM file is usually only readable by root (it has the
- private key afterall), so you'll need to relax the permissions or make
- a copy that the user running x11vnc/stunnel can read.
-
-
- SSL VNC Viewers:
-
- Regarding VNC viewers that "natively" do SSL unfortunately there do
- not seem to be many. The SingleClick UltraVNC Java Viewer is SSL and
- is compatible with x11vnc's -ssl option and stunnel.) Commercial
- versions of VNC seem to have some SSL-like encryption built in, but we
- haven't tried those either and they probably wouldn't work since their
- (proprietary) SSL-like negotiation is likely embedded in the VNC
- protocol unlike our case where it is external.
-
- Note: as of Mar/2006 libvncserver/x11vnc provides a SSL-enabled Java
- applet that can be served up via the -httpdir or -http options when
- -ssl is enabled. It will also be served via HTTPS via either the VNC
- port (e.g. https://host:5900/) or a 2nd port via the -https option.
-
- In general current SSL VNC solutions are not particularly "seemless".
- But it can be done, and with a wrapper script on the viewer side and
- the -stunnel or -ssl option on the server side it works well and is
- convenient. Here is a simple script ss_vncviewer that automates
- running stunnel on the VNC viewer side on Unix a little more carefully
- than the commands printed above. (One could probably do a similar
- thing with a .BAT file on Windows in the stunnel folder.)
-
- Update Jul/2006: we now provide an Enhanced TightVNC Viewer (SSVNC)
- package that starts up STUNNEL automatically along with some other
- features. All binaries (stunnel, vncviewer, and some utilities) are
- provided in the package. It works on Unix, Mac OS X, and Windows.
-
-
- Q-53: Does x11vnc have built-in SSL tunneling?
-
- You can read about non-built-in methods in the Previous FAQ for
- background.
-
- SSL tunnels provide an encrypted channel without the need for Unix
- users, passwords, and key passphrases required for ssh (and at the
- other extreme SSL can also provide a complete signed certificate chain
- of trust.) On the other hand, since SSH is usually installed
- everywhere and firewalls often let its port through, ssh is frequently
- the path of least resistance.
-
- Built-in SSL x11vnc options:
-
- As of Feb/2006 the x11vnc -ssl option automates the SSL tunnel
- creation on the x11vnc server side. An SSL-enabled Java Viewer applet
- is also provided that can be served via HTTP or HTTPS to automate SSL
- on the client side.
-
- The -ssl mode uses the www.openssl.org library if available at build
- time.
-
- The mode requires an SSL certificate and key (i.e. .pem file.) These
- are usually created via the openssl(1) program (in fact in for "-ssl"
- (same as "-ssl SAVE") it will run openssl for you automatically.) So
- the SSL is not completely "built-in" since this external tool needs to
- be installed, but at least x11vnc runs it for you automatically.
-
- An -ssl example:
- x11vnc -display :0 -ssl -passwdfile ~/mypass
-
- You'll get output like this:
- 09/04/2006 19:27:35 Creating a self-signed PEM certificate...
- 09/04/2006 19:27:35
- ...
-
- The SSL VNC desktop is: far-away.east:0
- PORT=5900
- SSLPORT=5900
-
- In this case openssl(1) was used to create a PEM automatically. It
- will prompt you if you want to protect it with with a passphrase. Use
- "-ssl SAVE_NOPROMPT" to not be prompted. Use "-ssl TMP" to create a
- temporary self-signed cert that will be discarded when x11vnc exits.
-
- Update: As of Nov/2008 x11vnc also supports the VeNCrypt SSL/TLS
- tunnel extension to the VNC protocol. The older ANONTLS method (vino)
- is also supported. This support is on by default when the -ssl option
- is in use and can be fine-tuned using these options: -vencrypt,
- -anontls, and -sslonly.
-
- The normal x11vnc -ssl operation is somewhat like a URL method
- vncs://hostname if vnc://hostname indicates a standard unencrypted VNC
- connection. Just as https://hostname is an SSL encrypted version of
- http://hostname. The entire VNC session goes through the SSL tunnel.
- VeNCrypt, on the other hand, switches to SSL/TLS early in the VNC
- protocol handshake. x11vnc 0.9.6 supports both simultaneously when
- -ssl is active.
-
-
- SSL VNC Viewers:. Viewer-side will need to use SSL as well. See the
- next FAQ and here for SSL enabled VNC Viewers, including SSVNC, to
- connect to the above x11vnc via SSL.
-
-
- As seen above, the PEM (privacy enhanced mail) file does not need to
- be supplied if the openssl(1) command is available in PATH, in that
- case a self-signed, certificate good the current and subsequent x11vnc
- sessions is created (this may take a while on very slow machines.)
-
- In general, the PEM file contains both the Certificate (i.e. public
- key) and the Private Key. Because of the latter, the file should be
- protected from being read by untrusted users. The best way to do this
- is to encrypt the key with a passphrase (note however this requires
- supplying the passphrase each time x11vnc is started up.)
-
- See the discussion on x11vnc Key Management for some utilities
- provided for creating and managing certificates and keys and even for
- creating your own Certificate Authority (CA) for signing VNC server
- and client certificates. This may be done by importing the certificate
- into Web Browser or Java plugin keystores, or pointing stunnel to it.
- The wrapper script ss_vncviewer provides an example on unix (see the
- -verify option.)
-
- Here are some notes on the simpler default (non-CA) operation. To have
- x11vnc save the generated certificate and key, use the "SAVE" keyword
- like this:
- x11vnc -ssl SAVE -display :0 ...
-
- (this is the same as the default: "-ssl".) This way it will be saved
- in the default directory ~/.vnc/certs/ as server.crt (the certificate
- only) and server.pem (both certificate and private key.) This opens up
- the possibility of copying the server.crt to machines where the VNC
- Viewer will be run to enable authenticating the x11vnc SSL VNC server
- to the clients. When authentication takes place this way (or via the
- more sophisticated CA signing described here), then
- Man-In-The-Middle-Attacks are prevented. Otherwise, the SSL encryption
- only provides protection against passive network traffic "sniffing"
- (i.e. you are not protected against M-I-T-M attacks.) Nowadays, most
- people seem mostly concerned mainly about passive sniffing (and the
- default x11vnc SSL mode protects against it.) Note that there are
- hacker tools like dsniff/webmitm and cain that implement SSL
- Man-In-The-Middle attacks. They rely on the client not bothering to
- check the cert.
-
-
- One can test to some degree that SSL is working after starting x11vnc
- with the -stunnel or -ssl option. From another machine one can use the
- openssl command something like this:
- openssl s_client -debug -msg -showcerts -connect far-away.east:5900
-
- After all of the debugging output and informational messages you'll
- see the string "RFB 003.008" that came from x11vnc. Pointing a web
- browser connecting to: https://far-away.east:5900/ and then viewing
- the SSL certificate information about the connection in the panels
- will also work.
-
- Note: If you serve up the SSL enabled Java VNC Viewer via something
- like:
- x11vnc -ssl -httpdir /usr/local/share/x11vnc/classes/ssl
-
- (or just the -http option), you can test it out completely using that,
- including using https to download it into the browser and connect to
- x11vnc.
-
-
- The older -stunnel option: Before the -ssl option there was a
- convenience option -stunnel that would start an external SSL tunnel
- for you using stunnel. The -ssl method is the preferred way, but for
- historical reference we keep the -stunnel info here.
-
- The -stunnel mode requires the stunnel.mirt.net command stunnel(8) to
- be installed on the system.
-
- Some -stunnel examples:
- x11vnc -display :0 -stunnel /path/to/stunnel.pem -passwdfile ~/mypass
-
- x11vnc -display :0 -stunnel SAVE ...
-
- You'll get output like this:
- The VNC desktop is: localhost:50
- The SSL VNC desktop is: far-away.east:0
- PORT=5950
- SSLPORT=5900
-
- That indicates stunnel is listening on port 5900 for incoming
- SSL-wrapped VNC connections from viewers. x11vnc is listening for
- local connections on port 5950 in this case (remote viewers cannot
- connect to it directly.) For -stunnel to work the stunnel command must
- be installed on the machine and available in PATH (note stunnel is
- often installed in sbin directories rather than bin.) Note that the
- default "-stunnel" by itself creates a temporary cert (as in "-ssl
- TMP".)
-
-
- Q-54: How do I use VNC Viewers with built-in SSL tunneling?
-
- Notes on using "native" VNC Viewers with SSL:
-
- There aren't any native VNC Viewers that do SSL (ask your VNC viewer
- developer to add the feature.) So a tunnel must be setup that you
- point the VNC Viewer to. This is often STUNNEL. You can do this
- manually, or use the ss_vncviewer script on Unix, or our Enhanced
- TightVNC Viewer (SSVNC) package on Unix, Windows, or MacOSX. See the
- next section for Java Web browser SSL VNC Viewers (you only need a
- Java-enabled Web browser for it to work.)
-
- Notes on the SSL enabled Java VNC Viewer provided in x11vnc
- classes/ssl/VncViewer.jar:
-
- A Java applet VNC Viewer allows you to connect to a VNC Server from a
- Java-enabled Web browser.
-
- The SSL enabled Java VNC Viewer (VncViewer.jar) in the x11vnc package
- supports only SSL based connections by default. As mentioned above the
- -httpdir can be used to specify the path to .../classes/ssl. A typical
- location might be /usr/local/share/x11vnc/classes/ssl. Or -http can be
- used to try to have it find the directory automatically.
-
- Also note that the SingleClick UltraVNC Java Viewer is compatible with
- x11vnc's -ssl SSL mode. (We tested it this way: "java -cp
- ./VncViewer.jar VncViewer HOST far-away.east PORT 5900 USESSL 1
- TRUSTALL 1")
-
- The Java viewer uses SSL to communicate securely with x11vnc. Note
- that the applet can optionally also be downloaded into your web
- browser via HTTPS (which is HTTP over SSL.) This way the HTML page and
- the Java applet itself are also delivered securely with SSL (as
- opposed to only the VNC traffic being encrypted with SSL.)
-
- For this case the output will be something like this:
- x11vnc -ssl SAVE -http
- ...
- The SSL VNC desktop is: far-away.east:0
- Java SSL viewer URL: https://far-away.east:5900/
- Java SSL viewer URL: http://far-away.east:5800/
- PORT=5900
- SSLPORT=5900
-
- Indicating the two URLs (the first one encrypted, the second not) one
- could point the web browser at to get the VNC viewer applet. E.g. put
- this
- http://far-away.east:5800/
-
- or:
- https://far-away.east:5900/
-
- into your Java-enabled Web browser.
-
- Note that KDE's Konqueror web browser seems to have problems with
- https Java applets, so you'll have to use the http/5800 with it (if
- you get https/5900 working let us know how you did it.)
-
- If you are using a router/firewall with port-redirection, and you are
- redirecting ports other than the default ones (5800, 5900) listed
- above see here.
-
- The https service provided thru the actual VNC port (5900 in the above
- example) can occasionally be slow or unreliable (it has to read some
- input and try to guess if the connection is VNC or HTTP.) If it is
- unreliable for you and you still want to serve the Java applet via
- https, use the -https option to get an additional port dedicated to
- https (its URL will also be printed in the output.)
-
- Another possibility is to add the GET applet parameter:
- https://far-away.east:5900/?GET=1
-
- This will have the VNC Viewer send a special HTTP GET string "GET
- /request.https.vnc.connection HTTP/1.0" that x11vnc will notice more
- quickly as a request for a VNC connection. Otherwise it must wait for
- a timeout to expire before it assumes a VNC connection.
-
- You may also use "urlPrefix=somestring" to have /somestring prepended
- to /request.https.vnc.connection". Perhaps you are using a web server
- proxy scheme to enter a firewall or otherwise have rules applied to
- the URL. If you need to have any slashes "/" in "somestring" use
- "_2F_" (a deficiency in libvncserver prevents using the more natural
- "%2F".)
-
- You apply multiple applet parameters in the regular URL way, e.g.:
- https://far-away.east:5900/?GET=1&urlPrefix=mysubdir&...
-
- All of the x11vnc Java Viewer applet parameters are described in the
- file classes/ssl/README
-
-
- Tips on Getting the SSL Java Applet Working the First Time:
- Unfortunately, it can be a little tricky getting the SSL VNC Java
- Viewer working with x11vnc. Here are some tips to getting working the
- first time (afterwards you can incrementally customize with more
- complex settings.)
- * First try it on the LAN: Do NOT try to have it work the first time
- going through firewalls, Web proxies, home router port
- redirections, or Apache portal. Just try a direct connection over
- your LAN first (if you only have 1 machine and no LAN, just do a
- direct connection to the same machine: localhost.) If the LAN
- machine you run x11vnc on has its own host-level firewall (most
- linux machine come with that on by default), disable it or at
- least let tcp ports 5800-6000 through.
- * First try HTTP to download the Java Applet: x11vnc can serve both
- the Java Applet jar file and VNC out of the same port (both
- tunneled through SSL, see below.) But it can lead to timing and
- other problems. So first try HTTP instead of HTTPS to download the
- Applet jar file (VncViewer.jar.) That is to say try
- http://hostname:5800 in your web browser first before trying
- https://hostname:5900. x11vnc will print out the ports and URLs it
- is using, so use the HTTP one it prints out.
- * Always Restart the Browser: If you are having failures and have to
- repeatedly retry things ALWAYS restart the browser (i.e.
- completely exit it and then start a new browser process) each
- time. Otherwise as you are changing things the browser may
- "remember" failed applet downloads, etc. and just add to the
- confusion and irreproducibility. If you see it trying to download
- VncViewer.class (instead of VncViewer.jar) you know it is really
- confused and needs to be restarted.
- * Step Lively: If you get Browser or Java VM or VNC Viewer applet
- dialog boxes saying things like "Do you want to trust this
- certificate?" or "The hostname does not match the one on the
- certificate", etc. just go through them as quickly as possible.
- x11vnc cannot wait forever for each SSL connection, and so if you
- dawdle too long inspecting the certs, etc it can lead to problems.
- Get it working first before taking your time to read the details
- in the dialogs, etc.
- * No inetd, Please: Even if you intend to deploy via inetd or xinetd
- eventually, get that working later (and remember do not use
- something like "-ssl TMP" that creates a new temporary SSL
- certificate for every new socket connection.)
- * Nothing Fancy: Do not try fancy stuff like -svc, -create, -unixpw,
- "-users unixpw=", "-users sslpeer=", -sslverify, etc. Just get the
- simplest connection working first and then incrementally add what
- you need.
-
- So the recommended test command lines are:
- x11vnc -ssl SAVE -http
- x11vnc -ssl SAVE -httpdir /path/to/x11vnc/classes/ssl
-
- Use the latter if x11vnc cannot automatically find the classes/ssl
- directory (this what the -http option instructs it to do.) Then point
- your browser to the HTTP (not HTTPS) URL it prints out.
-
- Following the above guidelines, did it work? If so, Congratulations!!
- you created an SSL encrypted connection between the SSL Java applet
- running in your web browser and x11vnc. The fact that you used HTTP
- instead of HTTPS to download the applet is not the end of the world
- (some users do it this way), the main thing is that the VNC traffic is
- encrypted with SSL. If you are having trouble even with the above
- baseline test case feel free to contact me (please send the Full
- x11vnc output, not just part of it; the complete x11vnc command line;
- the URL(s) entered in the browser; the full Java Console output; and
- anything else you can think of.)
-
- Next, you can add the features you want one by one testing it still
- works each time. I suggest first turning on the HTTPS applet download
- (https://hostname:5900) if that is what you intend to use. That one
- gives the most trouble because of the ambiguity of passing two
- different protocols (HTTP and VNC) through the same SSL service port.
-
- Next, turn on inetd if you intend to use that (this can be tricky too,
- be sure to use -oa logfile and inspect it carefully if there are
- problems.) If you are going to use non-standard ports (e.g. "-rfbport
- 443" as root), work on that next. Then enable the firewall, router
- port redirection channel (you will somehow need to be outside to do
- that, maybe test that through another VNC session.)
-
- Then, if you plan to use them, enable "fancy stuff" like "-svc" or
- "-unixpw", etc, etc. Be sure to add a password either "-rfbauth" or
- "-unixpw" or both. If you need to have the web browser use a corporate
- Web Proxy (i.e. it cannot connect directly) work on that last. Ditto
- for the Apache portal.
-
-
- Router/Firewall port redirs: If you are doing port redirection at
- your router to an internal machine running x11vnc AND the internet
- facing port is different from the internal machine's VNC port, you
- will need to apply the PORT applet parameter to indicate to the applet
- the Internet facing port number (otherwise by default the internal
- machine's port, say 5900, is sent and that of course is rejected at
- the firewall/router.) For example:
- https://far-away.east:443/?GET=1&PORT=443
-
- So in this example the user configures his router to redirect
- connections to port 443 on his Internet side to, say, port 5900 on the
- internal machine running x11vnc. See also the -httpsredir option that
- will try to automate this for you.
-
- To configure your router to do port redirection, see its instructions.
- Typically, from the inside you point a web browser to a special URL
- (e.g. http://192.168.1.1) and you get a web interface to configure it.
- Look for something like "Port Redirection" or "Port Forwarding",
- probably under "Advanced" or something like that. If you have a Linux
- or Unix system acting as your firewall/router, see its firewall
- configuration.
-
- You can also use x11vnc options -rfbport NNNNN and -httpport NNNNN to
- match the ports that your firewall will be redirecting to the machine
- where x11vnc is run.
-
-
- Tedious Dialogs: If you do serve the SSL enabled Java viewer via https
- be prepared for quite a number of "are you sure you trust this site?"
- dialogs:
- * First from the Web browser that cannot verify the self-signed
- certificate when it downloads index.vnc.
- * From the Web browser again noting that the common name on the
- certificate does not match the hostname of the remote machine.
- * Next from the Java VM that cannot verify the self-signed
- certificate when it downloads VncViewer.jar.
- * And also from the Java VM again noting that the common name on the
- certificate does not match the hostname of the remote machine.
- * Finally from the Java VncViewer applet itself saying it cannot
- verify the certificate! (or a popup asking you if you want to see
- the certificate.)
-
- Note that sometimes if you pause too long at one of the above dialogs
- then x11vnc may exceed a timeout and assume the current socket
- connection is VNC instead of the HTTPS it actually is (but since you
- have paused too long at the dialog the GET request comes too late.)
- Often hitting Reload and going through the dialogs more quickly will
- let you connect. The Java VM dialogs are the most important ones to
- NOT linger at. If you see in the x11vnc output a request for
- VncViewer.class instead of VncViewer.jar it is too late... you will
- need to completely restart the Web browser to get it to try for the
- jar again. You can use the -https option if you want a dedicated port
- for HTTPS connections instead of sharing the VNC port.
-
- To see example x11vnc output for a successful https://host:5900/
- connection with the Java Applet see This Page. And here is a newer
- example including the Java Console output.
-
- All of the x11vnc Java Viewer applet parameters are described in the
- file classes/ssl/README
-
-
- Notes on the VNC Viewer ss_vncviewer wrapper script:
-
- If you want to use a native VNC Viewer with the SSL enabled x11vnc you
- will need to run an external SSL tunnel on the Viewer side. There do
- not seem to be any native SSL VNC Viewers outside of our x11vnc and
- SSVNC packages. The basic ideas of doing this were discussed for
- external tunnel utilities here.
-
- The ss_vncviewer script provided with x11vnc and SSVNC can set up the
- stunnel tunnel automatically on unix as long as the stunnel command is
- installed on the Viewer machine and available in PATH (and vncviewer
- too of course.) Note that on a Debian based system you will need to
- install the package stunnel4 not stunnel. You can set the environment
- variables STUNNEL and VNCVIEWERCMD to point to the correct programs if
- you want to override the defaults.
-
- Here are some examples:
- 1) ss_vncviewer far-away.east:0
-
- 2) ss_vncviewer far-away.east:0 -encodings "copyrect tight zrle hextile"
-
- 3) ss_vncviewer -verify ./server.crt far-away.east:0
-
- 4) ss_vncviewer -mycert ./client.pem far-away.east:0
-
- 5) ss_vncviewer -proxy far-away.east:8080 myworkstation:0
-
- The first one is the default mode and accepts the x11vnc certificate
- without question. The second one is as the first, but adds the
- -encodings options to the vncviewer command line.
-
- The third one requires that the x11vnc server authenticate itself to
- the client against the certificate in the file ./server.crt (e.g. one
- created by "x11vnc -ssl SAVE" and safely copied to the VNC viewer
- machine.)
-
- The fourth one is for VNC Viewer authentication, it uses ./client.pem
- to authenticate itself to x11vnc. One can supply both -verify and
- -mycert simultaneously.
-
- The fifth one shows that Web proxies can be used if that is the only
- way to get out of the firewall. If the "double proxy" situation arises
- separate the two by commas. See this page for more information on how
- Web proxies come into play.
-
- If one uses a Certificate Authority (CA) scheme described here, the
- wrapper script would use the CA cert instead of the server cert:
- 3') ss_vncviewer -verify ./cacert.crt far-away.east:0
-
- Update Jul/2006: we now provide an Enhanced TightVNC Viewer (SSVNC)
- package that starts up STUNNEL automatically along with some other
- features. All binaries (stunnel, vncviewer, and some utilities) are
- provided in the package. It works on Unix, Mac OS X, and Windows.
-
-
- Q-55: How do I use the Java applet VNC Viewer with built-in SSL
- tunneling when going through a Web Proxy?
- The SSL enabled Java VNC Viewer and firewall Proxies:
-
- SSL and HTTPS aside, there is a general problem with Firewall Proxies
- and Java Applets that open sockets. The applet is downloaded
- successfully (through the browser) using HTTP and the proxy, but when
- the applet tries to reconnect to the originating host (the only one
- allowed by security) it does not use the proxy channel. So it cannot
- reconnect to the server the applet came from!
-
- We have found a convenient workaround: in the directory where
- VncViewer.jar resides there is a digitally signed version of the same
- applet called SignedVncViewer.jar. Since the applet is digitally
- signed, there will be an additional dialog from the Java VM plugin
- asking you if you want to trust the applet fully.
-
- You should say "Yes". If you do, the applet will be run in a mode
- where it can try to determine the firewall proxy host name and port
- (it will ask you for them if it cannot find them.) This way it can
- connect directly to the Proxy and then request the CONNECT method to
- be redirected to the originating host (the x11vnc VNC Server.) SSL is
- then layered over this socket.
-
- To do this you should use the proxy.vnc HTML file like via this URL in
- your browser:
- https://yourmachine.com:5900/proxy.vnc
-
- (instead of the unsigned one in https://yourmachine.com:5900/ that
- gives the default index.vnc)
-
- Proxies that limit CONNECT to ports 443 and 563:
-
- Things become trickier if the Web proxy restricts which CONNECT ports
- can be redirected to. For security, some (most?) proxies only allow
- port 443 (HTTPS) and 563 (SNEWS) by default. In this case, the only
- thing to do is run x11vnc on that low port, e.g. "-rfbport 443", (or
- use a port redirection on, say, a firewall or router port 443 to the
- internal machine.)
-
- If you do such a redirection to an internal machine and x11vnc is not
- listening on port 443, you will probably need to edit proxy.vnc.
- Suppose the SSL x11vnc server was listening on port 5901. You should
- change the line in proxy.vnc from:
- <param name=PORT value=$PORT>
-
- to:
- <param name=PORT value=443>
-
- Since otherwise $PORT will be expanded to 5901 by x11vnc and the
- viewer applet will fail to connect to that port on the firewall.
-
- Another way to achieve the same thing is to use the applet PORT
- parameter:
- https://yourmachine.com/proxy.vnc?PORT=443
-
- this is cleaner because it avoids editing the file, but requires more
- parameters in the URL. See also the -httpsredir x11vnc option that
- will try to automate this for you. To use the GET trick discussed
- above, do:
- https://yourmachine.com/proxy.vnc?GET=1&PORT=443
-
- All of the x11vnc Java Viewer applet parameters are described in the
- file classes/ssl/README
-
- Here is an example of Java Console and x11vnc output for the Web proxy
- case.
-
-
- Note that both the ss_vncviewer stunnel Unix wrapper script and
- Enhanced TightVNC Viewer (SSVNC) can use Web proxies as well even
- though they do not involve a Web browser.
-
-
- Q-56: Can Apache web server act as a gateway for users to connect via
- SSL from the Internet with a Web browser to x11vnc running on their
- workstations behind a firewall?
- Yes. You will need to configure apache to forward these connections.
- It is discussed here. This SSL VNC portal provides a clean alternative
- to the traditional method where the user uses SSH to log in through
- the gateway to create the encrypted port redirection to x11vnc running
- on her desktop.
-
- Also see the desktop.cgi CGI script method that achieves much of what
- this Apache VNC SSL portal method does (as long as desktop.cgi's 'port
- redirection' mode is enabled.)
-
-
- Q-57: Can I create and use my own SSL Certificate Authority (CA) with
- x11vnc?
- Yes, see this page for how to do this and the utility commands x11vnc
- provides to create and manage many types of certificates and private
- keys.
-
-
-
- [Display Managers and Services]
-
- Q-58: How can I run x11vnc as a "service" that is always available?
-
- There are a number of ways to do this. The primary thing you need to
- decide is whether you want x11vnc to connect to the X session on the
- machine 1) regardless of who (or if anyone) has the X session, or 2)
- only if a certain user has the X session. Because X sessions are
- protected by X permissions (MIT-MAGIC-COOKIE files XAUTHORITY and
- $HOME/.Xauthority) the automatically started x11vnc will of course
- need to have sufficient permissions to connect to the X display.
-
- Here are some ideas:
- * Use the description under "Continuously" in the FAQ on x11vnc and
- Display Managers
- * Use the description in the FAQ on x11vnc and inetd(8)
- * Use the description in the FAQ on Unix user logins and inetd(8)
- * Start x11vnc from your $HOME/.xsession (or $HOME/.xinitrc or
- autostart script or ...)
- * Although less reliable, see the x11vnc_loop rc.local hack below.
-
- The display manager scheme will not be specific to which user has the
- X session unless a test is specifically put into the display startup
- script (often named Xsetup.) The inetd(8) scheme may or may not be
- specific to which user has the X session (and it may not be able to do
- all users via the XAUTHORITY permission issues.)
-
- The .xsession/.xinitrc scheme is obviously is specific to a particular
- user and only when they are logged into X. If you do not know what a
- $HOME/.xsession script is or how to use one, perhaps your desktop has
- a "session startup commands" configuration option. The command to be
- run in the .xsession or .xinitrc file may look like this:
-x11vnc -logfile $HOME/.x11vnc.log -rfbauth $HOME/.vnc/passwd -forever -bg
-
- plus any other options you desire.
-
- Depending on your desktop and/or OS/distribution the automatically run
- X startup scripts (traditionally .xsession/.xinitrc) may have to be in
- a different directory or have a different basename. One user
- recommends the description under 'Running Scripts Automatically' at
- this link.
-
- Firewalls: note all methods will require the host-level firewall to be
- configured to allow connections in on a port. E.g. 5900 (default VNC
- port) or 22 (default SSH port for tunnelling VNC.) Most systems these
- days have firewalls turned on by default, so you will actively have to
- do something to poke a hole in the firewall at the desired port
- number. See your system administration tool for Firewall settings
- (Yast, Firestarter, etc.)
-
-
- Q-59: How can I use x11vnc to connect to an X login screen like xdm,
- GNOME gdm, KDE kdm, or CDE dtlogin? (i.e. nobody is logged into an X
- session yet.)
-
- We describe two scenarios here. The first is called 'One time only'
- meaning you just need to do it quickly once and don't want to repeat;
- and the second is called 'Continuously' meaning you want the access to
- be available after every reboot and after every desktop logout.
- _________________________________________________________________
-
- One time only: If the X login screen is running and you just want to
- connect to it once (i.e. a one-shot):
-
- It is usually possible to do this by just adjusting the XAUTHORITY
- environment variable to point to the correct MIT-COOKIE auth file
- while running x11vnc as root, e.g. for the gnome display manager, GDM:
- x11vnc -auth /var/gdm/:0.Xauth -display :0
-
- (the -auth option sets the XAUTHORITY variable for you.)
-
- There will be a similar thing to do for xdm using however a different
- auth directory path (perhaps something like
- /var/lib/xdm/authdir/authfiles/A:0-XQvaJk) for the xdm greeter or
- /var/lib/kdm/A:0-crWk72 (or /var/run/xauth/A:0-qQPftr, etc. etc) for
- the kdm greeter. Of course, the random characters in the file basename
- will vary and you will need to use the actual filename on your system.
- Read your system docs to find out where the display manager cookie
- files are kept.
-
- Trick: sometimes ps(1) can reveal the X server process -auth argument
- (e.g. "ps wwaux | grep auth") and hence the path to the auth file.
-
- x11vnc must be run as root for this because the /var/gdm/:0.Xauth,
- /var/lib/kdm/A:0-crWk72, etc. auth files are only readable by root. If
- you do not want to run x11vnc as root, you can copy (as root or sudo)
- the auth file to some location and make it readable by your userid.
- Then run x11vnc as your userid with -auth pointed to the copied file.
-
- Update Dec/2009: use "-auth guess" to have x11vnc try to guess the
- location of the auth file for you.
-
- You next connect to x11vnc with a VNC viewer, give your username and
- password to the X login prompt to start your session.
-
- Note: GDM: gdm seems to have an annoying setting that causes x11vnc
- (and any other X clients) to be killed after the user logs in. Setting
- KillInitClients=false in the [daemon] section of /etc/X11/gdm/gdm.conf
- (or /etc/gdm/gdm.conf, etc.) avoids this. Otherwise, just restart
- x11vnc and then reconnect your viewer. Other display managers (kdm,
- etc) may also have a similar problem. One user reports having to alter
- "gdm.conf-custom" as well.
-
- Note: Solaris: For dtlogin in addition to the above sort of trick
- (BTW, the auth file should be in /var/dt), you'll also need to add
- something like Dtlogin*grabServer:False to the Xconfig file
- (/etc/dt/config/Xconfig or /usr/dt/config/Xconfig on Solaris, see the
- example at the end of this FAQ.) Then restart dtlogin, e.g.:
- /etc/init.d/dtlogin stop; /etc/init.d/dtlogin start or reboot.
-
- Update Nov/2008: Regarding GDM KillInitClients: see the -reopen option
- for another possible workaround.
-
- Update Oct/2009: Regarding GDM KillInitClients: starting with x11vnc
- 0.9.9 it will try to apply heuristics to detect if a window manager is
- not running (i.e. whether the Display Manager Greeter Login panel is
- still up.) If it thinks the display manager login is still up it will
- delay creating windows or using XFIXES. The former is what GDM uses to
- kill the initial clients, use of the latter can cause a different
- problem: an Xorg server crash. So with 0.9.9 and later it should all
- work without needing to set KillInitClients=false (which is a good
- because recent GDM, v2.24, has removed this option) or use -noxfixes.
- To disable the heuristics and delaying set X11VNC_AVOID_WINDOWS=never;
- to set the delay time explicitly use, e.g., X11VNC_AVOID_WINDOWS=120
- (delays for 120 seconds after the VNC connection; you have that long
- to log in.)
- _________________________________________________________________
-
- Continuously: Have x11vnc reattach each time the X server is
- restarted (i.e. after each logout and reboot):
-
- To make x11vnc always attached to the X server including the login
- screen you will need to add a command to a display manager startup
- script.
-
- Please consider the security implications of this! The VNC display for
- the X session always accessible (but hopefully password protected.)
- Add -localhost if you only plan to access via a SSH tunnel.
-
- The name of the display manager startup script file depends on desktop
- used and seem to be:
- GDM (GNOME) /etc/X11/gdm/Init/Default
- /etc/gdm/Init/Default
- KDM (KDE) /etc/kde*/kdm/Xsetup
- XDM /etc/X11/xdm/Xsetup (or sometimes xdm/Xsetup_0)
- CDE /etc/dt/config/Xsetup
-
- although the exact location can be operating system, distribution, and
- time dependent. See the documentation for your display manager:
- gdm(1), kdm(1), xdm(1), dtlogin(1) for additional details. There may
- also be display number specific scripts: e.g. Xsetup_0 vs. Xsetup, you
- need to watch out for.
-
- Note: You should read and understand all of the Note's and Update's
- in the 'One time only' section above. All of the GDM topics apply here
- as well:
-
- Note: GDM: The above (in 'One time only') gdm setting of
- KillInitClients=false in /etc/X11/gdm/gdm.conf (or /etc/gdm/gdm.conf,
- etc.) for GDM is needed here as well. Other display managers (KDM,
- etc) may also have a similar problem.
-
- Also see the Update Oct/2009 above where x11vnc 0.9.9 and later
- automatically avoids being killed.
-
- Note: DtLogin: The above (in 'One time only')
- Dtlogin*grabServer:False step for Solaris will be needed for dtlogin
- here as well.
-
- In any event, the line you will add to the display manager script
- (Xsetup, Default, or whatever) will look something like:
- /usr/local/bin/x11vnc -rfbauth /path/to/the/vnc/passwd -o /var/log/x11vnc.log
- -forever -bg
-
- where you should customize the exact command to your needs (e.g.
- -localhost for SSH tunnel-only access; -ssl SAVE for SSL access; etc.)
-
- Happy, happy, joy, joy: Note that we do not need to specify -display
- or -auth because happily they are already set for us in the DISPLAY
- and XAUTHORITY environment variables for the Xsetup script!!!
-
- You may also want to force the VNC port with something like "-rfbport
- 5900" (or -N) to avoid autoselecting one if 5900 is already taken.
- _________________________________________________________________
-
- Fedora/gdm: Here is an example of what we did on a vanilla install of
- Fedora-C3 (seems to use gdm by default.) Add a line like this to
- /etc/X11/gdm/Init/:0
- /usr/local/bin/x11vnc -rfbauth /etc/x11vnc.passwd -forever -bg -o /var/log/x1
-1vnc.log
-
- And then add this line to /etc/X11/gdm/gdm.conf (or /etc/gdm/gdm.conf,
- etc.) in the [daemon] section:
- KillInitClients=false
-
- Then restart: /usr/sbin/gdm-restart (or reboot.) The
- KillInitClients=false setting is important: without it x11vnc will be
- killed immediately after the user logs in. Here are full details on
- how to configure gdm
- _________________________________________________________________
-
- Solaris/dtlogin: Here is an example of what we did on a vanilla
- install of Solaris:
- Make the directory /etc/dt/config:
- mkdir -p /etc/dt/config
-
- Copy over the Xconfig file for customization:
- cp /usr/dt/config/Xconfig /etc/dt/config/Xconfig
-
- Edit /etc/dt/config/Xconfig and uncomment the line:
- Dtlogin*grabServer: False
-
- Next, copy over Xsetup for customization:
- cp /usr/dt/config/Xsetup /etc/dt/config/Xsetup
-
- Edit /etc/dt/config/Xsetup and at the bottom put a line like:
- /usr/local/bin/x11vnc -forever -o /var/log/x11vnc.log -bg
-
- (tweaked to your local setup and preferences, a password via -rfbauth,
- etc. would be a very good idea.)
-
- Restart the X server and dtlogin:
- /etc/init.d/dtlogin stop
- /etc/init.d/dtlogin start
-
- (or reboot or maybe just restart the X session.)
- _________________________________________________________________
-
- KDM: One user running the kdm display manager reports putting this
- line:
- x11vnc -forever -rfbauth /home/xyz/.vnc/passwd -bg -o /var/log/x11vnc.log
-
- in /etc/kde/kdm/Xsetup. After rebooting the system it all seemed to
- work fine.
- _________________________________________________________________
-
-
- If you do not want to deal with any display manager startup scripts,
- here is a kludgey script that can be run manually or out of a boot
- file like rc.local: x11vnc_loop It will need some local customization
- before running. Because the XAUTHORITY auth file must be guessed by
- this script, use of the display manager script method described above
- is greatly preferred. There is also the -loop option that does
- something similar.
-
- If the machine is a traditional Xterminal you may want to read this
- FAQ.
-
- Firewalls: note all methods will require the host-level firewall to be
- configured to allow connections in on a port. E.g. 5900 (default VNC
- port) or 22 (default SSH port for tunnelling VNC.) Most systems these
- days have firewalls turned on by default, so you will actively have to
- do something to poke a hole in the firewall at the desired port
- number. See your system administration tool for Firewall settings
- (Yast, Firestarter, etc.)
-
-
- Q-60: Can I run x11vnc out of inetd(8)? How about xinetd(8)?
-
- Yes, perhaps a line something like this in /etc/inetd.conf will do it
- for you:
-
- 5900 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc_sh
-
- where the shell script /usr/local/bin/x11vnc_sh uses the -inetd option
- and looks something like (you'll need to customize to your settings.)
-#!/bin/sh
-/usr/local/bin/x11vnc -inetd -display :0 -auth /home/fred/.Xauthority \
- -rfbauth /home/fred/.vnc/passwd -o /var/log/x11vnc_sh.log
-
- Important: Note that you must redirect the standard error output to a
- log file (e.g. -o logfile) or "2>/dev/null" for proper operation via
- inetd (otherwise the standard error also goes to the VNC vncviewer,
- and that confuses it greatly, causing it to abort.) If you do not use
- a wrapper script as above but rather call x11vnc directly in
- /etc/inetd.conf and do not redirect stderr to a file, then you must
- specify the -q (aka -quiet) option: "/usr/local/bin/x11vnc -q -inetd
- ...". When you supply both -q and -inet and no "-o logfile" then
- stderr will automatically be closed (to prevent, e.g. library stderr
- messages leaking out to the viewer.) The recommended practice is to
- use "-o logfile" to collect the output in a file or wrapper script
- with "2>logfile" redirection because the errors and warnings printed
- out are very useful in troubleshooting problems.
-
- Note also the need to set XAUTHORITY via -auth to point to the
- MIT-COOKIE auth file to get permission to connect to the X display
- (setting and exporting the XAUTHORITY variable accomplishes the same
- thing.) See the x11vnc_loop file in the previous question for more
- ideas on what that auth file may be, etc. The scheme described in the
- FAQ on Unix user logins and inetd(8) works around the XAUTHORITY issue
- nicely.
-
- Note: On Solaris you cannot have the bare number 5900 in
- /etc/inetd.conf, you'll need to replace it with a word like x11vnc an
- then put something like "x11vnc 5900/tcp" in /etc/services.
-
- Since the process runs as root, it might be a bad idea to have the
- logfile in a world-writable area like /tmp if there are untrustworthy
- users on the machine. Perhaps /var/log is a better place.
-
- Be sure to look at your /etc/hosts.allow and /etc/hosts.deny settings
- to limit the machines that can connect to this service (your desktop!)
- For the above example with /etc/hosts.allow:
- x11vnc_sh : 123.45.67.89
-
- A really safe way to do things is to limit the above inetd to
- localhost only (via /etc/hosts.allow) and use ssh to tunnel the
- incoming connection. Using inetd for this prevents there being a tiny
- window of opportunity between x11vnc starting up and your vncviewer
- connecting to it. Always use a VNC password to further protect against
- unwanted access.
-
- For xinetd(8), one user reports he created the file
- /etc/xinetd.d/x11vncservice containing the following:
-# default: off
-# description:
-service x11vncservice
-{
- flags = REUSE NAMEINARGS
- port = 5900
- type = UNLISTED
- socket_type = stream
- protocol = tcp
- wait = no
- user = root
- server = /usr/sbin/tcpd
- server_args = /usr/local/bin/x11vnc_sh
- disable = no
-}
-
- With the contents of /usr/local/bin/x11vnc_sh similar to the example
- given above. One user reports this works with avoiding the wrapper
- script:
-service x11vncservice
-{
- port = 5900
- type = UNLISTED
- socket_type = stream
- protocol = tcp
- wait = no
- user = root
- server = /usr/local/bin/x11vnc
- server_args = -inetd -q -display :0 -auth /var/gdm/:0.Xauth
- disable = no
-}
-
- (or one can replace the -q with say "-o /var/log/x11vnc.log" to
- capture a log)
-
- The above works nicely for GDM because the -auth file is a fixed name.
- For KDM or XDM the filename varies. Here is one idea for a x11vnc_sh
- wrapper to try to guess the name:
-#!/bin/sh
-COLUMNS=256
-export COLUMNS
-authfile=`ps wwaux | grep '/X.*-auth' | grep -v grep | sed -e 's/^.*-auth *//'
--e 's/ .*$//' | head -n 1`
-
-if [ -r "$authfile" ]; then
- exec /usr/local/bin/x11vnc -inetd -o /var/log/x11vnc.log -display :0 -a
-uth "$authfile"
-fi
-exit 1
-
- Starting with x11vnc 0.9.3 this can be automated by:
-#!/bin/sh
-exec /usr/local/bin/x11vnc -inetd -o /var/log/x11vnc.log -find -env FD_XDM=1
-
-
- Q-61: Can I have x11vnc advertise its VNC service and port via mDNS /
- Zeroconf (e.g. Avahi) so VNC viewers on the local network can detect
- it automatically?
-
- Yes, as of Feb/2007 x11vnc supports mDNS / Zeroconf advertising of its
- service via the Avahi client library. Use the option -avahi (same as
- -mdns or -zeroconf) to enable it. Depending on your setup you may need
- to install Avahi (including the development/build packages), enable
- the server: avahi-daemon and avahi-dnsconfd, and possibly open up UDP
- port 5353 on your firewall.
-
- If the Avahi client library or build environment is not available at
- build-time, then at run-time x11vnc will try to look for external
- helper programs, avahi-browse(1) or dns-sd(1), to do the work.
-
- The service was tested with Chicken of the VNC ("Use Bonjour"
- selected) on a Mac on the same network and the service was noted and
- listed in the servers list. Clicking on it and then "Connect"
- connected automatically w/o having to enter any hostnames or port
- numbers.
-
- It appears SuSE 10.1 comes with avahi (or you can add packages, e.g.
- avahi-0.6.5-27) but not the development package (you can use the
- OpenSuSE avahi-devel rpm.) Unfortunately, you may need to disable
- another Zeroconf daemon "/etc/init.d/mdnsd stop", before doing
- "/etc/init.d/avahi-daemon start" and "/etc/init.d/avahi-dnsconfd
- start". We also had to comment out the browse-domains line in
- /etc/avahi/avahi-daemon.conf. Hopefully there is "LessConf" to do on
- other distros/OS's...
-
-
- Q-62: Can I have x11vnc allow a user to log in with her UNIX username
- and password and then have it find her X session display on that
- machine and then attach to it? How about starting an X session if one
- cannot be found?
-
- The easiest way to do this is via inetd(8) using the -unixpw and
- -display WAIT options. The reason inetd(8) makes this easier is that
- it starts a new x11vnc process for each new user connection. Otherwise
- a wrapper would have to listen for connections and spawn new x11vnc's
- (see this example and also the -loopbg option.) inetd(8) is not
- required for this, but it makes some aspects more general.
-
- Also with inetd(8) users always connect to a fixed VNC display, say
- hostname:0, and do not need to memorize a special VNC display number
- just for their personal use, etc.
-
- Update: Use the -find, -create, -svc, and -xdmsvc options that are
- shorthand for common FINDCREATEDISPLAY usage modes (e.g. terminal
- services) described below. (i.e. simply use "-svc" instead of the
- cumbersome "-display WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users
- unixpw= -ssl SAVE")
-
- The -display WAIT option makes x11vnc wait until a VNC viewer is
- connected before attaching to the X display.
-
- Additionally it can be used to run an external command that returns
- the DISPLAY and XAUTHORITY data. We provide some useful builtin ones
- (FINDDISPLAY and FINDCREATEDISPLAY below), but in principle one could
- supply his own script: "-display WAIT:cmd=/path/to/find_display" where
- the script find_display might look something like this.
-
- A default script somewhat like the above is used under "-display
- WAIT:cmd=FINDDISPLAY" (same as -find) The format for any such command
- is that it returns DISPLAY=:disp as the first line and any remaining
- lines are either XAUTHORITY=file or raw xauth data (the above example
- does the latter.) If applicable (-unixpw mode), the program is run as
- the Unix user name who logged in.
-
- On Linux if the virtual terminal is known the program appends ",VT=n"
- to the DISPLAY line; a chvt n will be attempted automatically. Or if
- only the X server process ID is known it appends ",XPID=n" (a chvt
- will be attempted by x11vnc.)
-
- Tip: Note that the -find option is an alias for "-display
- WAIT:cmd=FINDDISPLAY". Use it!
-
- The -unixpw option allows UNIX password logins. It conveniently knows
- the Unix username whose X display should be found. Here are a couple
- /etc/inetd.conf examples of this usage:
-5900 stream tcp nowait nobody /usr/sbin/tcpd /usr/local/bin/x11vnc -inetd
--unixpw \
- -find -o /var/log/x11vnc.log -ssl SAVE -ssldir /usr/local/certs
-5900 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc -inetd
--unixpw \
- -find -o /var/log/x11vnc.log -ssl SAVE -users unixpw=
-
- Note we have used the -find alias and the very long lines have been
- split. An alternative is to use a wrapper script, e.g.
- /usr/local/bin/x11vnc.sh that has all of the options. (see also the
- -svc alias.)
-
- In the first inetd line x11vnc is run as user "nobody" and stays user
- nobody during the whole session. The permissions of the log files and
- certs directory will need to be set up to allow "nobody" to use them.
-
- In the second one x11vnc is run as root and switches to the user that
- logs in due to the "-users unixpw=" option.
-
- Note that SSL is required for this mode because otherwise the Unix
- password would be passed in clear text over the network. In general
- -unixpw is not required for this sort of scheme, but it is convenient
- because it determines exactly who the Unix user is whose display
- should be sought. Otherwise the find_display script would have to use
- some method to work out DISPLAY, XAUTHORITY, etc (perhaps you use
- multiple inetd ports and hardwire usernames for different ports.)
-
- If you really want to disable the SSL or SSH -localhost constraints
- (this is not recommended unless you really know what you are doing:
- Unix passwords sent in clear text is a very bad idea...) read the
- -unixpw documentation.
-
- A inetd(8) scheme for a fixed user that doesn't use SSL or unix
- passwds could be:
- /usr/local/bin/x11vnc -inetd -users =fred -find -rfbauth /home/fred/.vnc/pass
-wd -o /var/log/x11vnc.log
-
- The "-users =fred" option will cause x11vnc to switch to user fred and
- then find his X display. The VNC password (-rfbauth) as opposed to
- Unix password (-unixpw) is used to authenticate the VNC client.
-
- Similar looking commands to the above examples can be run directly and
- do not use inetd (just remove the -inetd option and run from the
- cmdline, etc.)
-
-
- X Session Creation: An added (Nov/2006) extension to FINDDISPLAY is
- FINDCREATEDISPLAY where if it does not find an X display via the
- FINDDISPLAY method it will create an X server session for the user
- (i.e. desktop/terminal server.) This is the only time x11vnc actually
- tries to start up an X server (normally it just attaches to an
- existing one.)
-
- For virtual sessions you will need to install the Xvfb program (e.g.
- apt-get install xvfb) or our Xdummy program (see below.)
-
- By default it will only try to start up virtual (non-hardware) X
- servers: first Xvfb and if that is not available then Xdummy (included
- in the x11vnc source code.) Note that Xdummy only works on Linux
- whereas Xvfb works just about everywhere (and in some situations
- Xdummy must be run as root.) An advantage of Xdummy over Xvfb is that
- Xdummy supports RANDR dynamic screen resizing, which can be handy if
- the user accesses the desktop from different sized screens (e.g.
- workstation and laptop.)
-
- So an inetd(8) example might look like:
-5900 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc -inetd \
- -o /var/log/x11vnc.log -http -prog /usr/local/bin/x11vnc \
- -ssl SAVE -unixpw -users unixpw= -display WAIT:cmd=FINDCREATEDISPLAY
-
- Where the very long lines have been split. See below where that long
- and cumbersome last line is replaced by the -svc alias.
-
- The above mode will allow direct SSL (e.g. ss_vncviewer or SSVNC)
- access and also Java Web browers access via: https://hostname:5900/.
-
- Tip: Note that the -create option is an alias for "-display
- WAIT:cmd=FINDCREATEDISPLAY-Xvfb".
-
- Tip: Note that -svc is a short hand for the long "-ssl SAVE -unixpw
- -users unixpw= -display WAIT:cmd=FINDCREATEDISPLAY" part. Unlike
- -create, this alias also sets up SSL encryption and Unix password
- login.
-
- The above inetd example then simplifies to:
-5900 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc -inetd \
- -o /var/log/x11vnc.log -http -prog /usr/local/bin/x11vnc \
- -svc
-
- Tip: In addition to the usual unixpw parameters, inside the VNC viewer
- the user can specify after his username (following a ":" see -display
- WAIT for details) for FINDCREATEDISPLAY they can add "geom=WxH" or
- "geom=WxHxD" to specify the width, height, and optionally the color
- depth. E.g. "fred:geom=800x600" at the login: prompt. Also if the env.
- var X11VNC_CREATE_GEOM is set to the desired WxH or WxHxD that will be
- used by x11vnc.
-
- You can set the env. var X11VNC_SKIP_DISPLAY to a comma separated list
- of displays to ignore in the FINDDISPLAY process (to force creation of
- new displays in some cases.) The user logging in via the vncviewer can
- also set this via username:nodisplay=...)
-
- If you do not plan on using the Java Web browser applet you can remove
- the -http (and -prog) option since this will speed up logging-in by a
- few seconds (x11vnc will not have to wait to see if a connection is
- HTTPS or VNC.)
-
- For reference, xinetd format in the file, say, /etc/xinetd.d/x11vnc:
-service x11vnc
-{
- type = UNLISTED
- port = 5900
- socket_type = stream
- protocol = tcp
- wait = no
- user = root
- server = /usr/local/bin/x11vnc
- server_args = -inetd -o /var/log/x11vnc.log -http -prog /usr/local/
-bin/x11vnc -svc
- disable = no
-}
-
- To print out the script in this case use "-display
- WAIT:cmd=FINDCREATEDISPLAY-print". To change the preference of
- Xservers and which to try list them, e.g.: "-display
- WAIT:cmd=FINDCREATEDISPLAY-X,Xvfb,Xdummy" or use "-create_xsrv
- X,Xvfb,Xdummy". The "X" one means to try to start up a real, hardware
- X server, e.g. startx(1) (if there is already a real X server running
- this may only work on Linux and the chvt program may need to be run to
- switch to the correct Linux virtual terminal.) x11vnc will try to run
- chvt automatically if it can determine which VT should be switched to.
-
- XDM/GDM/KDM Login Greeter Panel: If you want to present the user with
- a xdm/gdm/kdm display manager "greeter" login you can use Xvfb.xdmcp
- instead of Xvfb, etc in the above list. However, you need to configure
- xdm/gdm/kdm to accept localhost XDMCP messages, this can be done by
- (from -help output):
- If you want the FINDCREATEDISPLAY session to contact an XDMCP login
- manager (xdm/gdm/kdm) on the same machine, then use "Xvfb.xdmcp"
- instead of "Xvfb", etc. The user will have to supply his username
- and password one more time (but he gets to select his desktop
- type so that can be useful.) For this to work, you will need to
- enable localhost XDMCP (udp port 177) for the display manager.
- This seems to be:
-
- for gdm in gdm.conf: Enable=true in section [xdmcp]
- for kdm in kdmrc: Enable=true in section [Xdmcp]
- for xdm in xdm-config: DisplayManager.requestPort: 177
-
- Unless you are also providing XDMCP service to xterminals or other
- machines, make sure that the host access list only allows local
- connections (the name of this file is often Xaccess and it is usually
- setup by default to do just that.) Nowadays, host level firewalling
- will also typically block UDP (port 177 for XDMCP) by default
- effectively limiting the UDP connections to localhost.
-
- Tip: Note that -xdmsvc is a short hand alias for the long "-ssl SAVE
- -unixpw -users unixpw= -display
- WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp". So we simply use:
-service x11vnc
-{
- type = UNLISTED
- port = 5900
- socket_type = stream
- protocol = tcp
- wait = no
- user = root
- server = /usr/local/bin/x11vnc
- server_args = -inetd -o /var/log/x11vnc.log -xdmsvc
- disable = no
-}
-
- (Note: use "-svc" instead of "-xdmsvc" for no XDMCP login greeter.)
-
-
- Local access (VNC Server and VNC Viewer on the same machine): To
- access your virtual X display session locally (i.e. while sitting at
- the same machine it is running on) one can perhaps have something like
- this in their $HOME/.xinitrc
-#!/bin/sh
-x11vnc -create -rfbport 5905 -env WAITBG=1
-vncviewer -geometry +0+0 -encodings raw -passwd $HOME/.vnc/passwd localhost:5
-
- You may not need the -passwd. Recent RealVNC viewers might be this:
-#!/bin/sh
-x11vnc -create -rfbport 5905 -env WAITBG=1
-vncviewer -FullScreen -PreferredEncoding raw -passwd $HOME/.vnc/passwd localhos
-t:5
-
- This way a bare X server is run with no window manager or desktop; it
- simply runs only the VNC Viewer on the real X server. The Viewer then
- draws the virtual X session on to the real one. On your system it
- might not be $HOME/.xinitrc, but rather .xsession, .Xclients, or
- something else. You will need to figure out what it is for your system
- and configuration.
-
- There may be a problem if the resolution (WxH) of the virtual X
- display does not match that of the physical X display.
-
- If you do not want to or cannot figure out the X startup script name
- (.xinitrc, etc) you could save the above commands to a shell script,
- say "vnclocal", and the log in via the normal KDM or GDM greeter
- program using the "Failsafe" option. Then in the lone xterm that comes
- up type "vnclocal" to connect to your virtual X display via x11vnc and
- vncviewer.
-
- _________________________________________________________________
-
- Summary: The "-display WAIT:cmd=FINDCREATEDISPLAY" scheme can be used
- to provide a "desktop service" (i.e. terminal service) on the server
- machine: you always get some desktop there, either a real hardware X
- server or a virtual one (depending on how you set things up.)
-
- So it provides simple "terminal services" based on Unix username and
- password. The created X server sessions (virtual or real hardware)
- will remain running after you disconnect the VNC viewer and will be
- found again on reconnecting via VNC and logging in. To terminate them
- use the normal way to Exit/LogOut from inside your X session. The user
- does not have to memorize which VNC display number is his. They all go
- the same one (e.g. hostname:0) and it switches based on username.
-
-
- Q-63: Can I have x11vnc restart itself after it terminates?
-
- One could do this in a shell script, but now there is an option -loop
- that makes it easier. Of course when x11vnc restarts it needs to have
- permissions to connect to the (potentially new) X display. This mode
- could be useful if the X server restarts often. Use e.g. "-loop5000"
- to sleep 5000 ms between restarts. Also "-loop2000,5" to sleep 2000 ms
- and only restart 5 times.
-
- One can also use the -loopbg to emulate inetd(8) to some degree, where
- each connected process runs in the background. It could be combined,
- say, with the -svc option to provide simple terminal services without
- using inetd(8).
-
-
- Q-64: How do I make x11vnc work with the Java VNC viewer applet in a
- web browser?
-
- To have x11vnc serve up a Java VNC viewer applet to any web browsers
- that connect to it, run x11vnc with this option:
- -httpdir /path/to/the/java/classes/dir
-
- (this directory will contain the files index.vnc and, for example,
- VncViewer.jar) Note that libvncserver contains the TightVNC Java
- classes jar file for your convenience. (it is the file
- classes/VncViewer.jar in the source tree.)
-
- You will see output something like this:
- 14/05/2004 11:13:56 Autoprobing selected port 5900
- 14/05/2004 11:13:56 Listening for HTTP connections on TCP port 5800
- 14/05/2004 11:13:56 URL http://walnut:5800
- 14/05/2004 11:13:56 screen setup finished.
- 14/05/2004 11:13:56 The VNC desktop is walnut:0
- PORT=5900
-
- then you can connect to that URL with any Java enabled browser. Feel
- free to customize the default index.vnc file in the classes directory.
-
- As of May/2005 the -http option will try to guess where the Java
- classes jar file is by looking in expected locations and ones relative
- to the x11vnc binary.
-
- Also note that if you wanted to, you could also start the Java viewer
- entirely from the viewer-side by having the jar file there and using
- either the java or appletviewer commands to run the program.
- java -cp ./VncViewer.jar VncViewer HOST far-away.east PORT 5900
-
- Proxies: See the discussion here if the web browser must use a web
- proxy to connect to the internet. It is tricky to get Java applets to
- work in this case: a signed applet must be used so it can connect to
- the proxy and ask for the redirection to the VNC server. One way to do
- this is to use the signed SSL one referred to in classes/ssl/proxy.vnc
- and set disableSSL=yes (note that this has no encryption; please use
- SSL or SSH as discuss elsewhere on this page) in the URL or the file.
-
-
- Q-65: Are reverse connections (i.e. the VNC server connecting to the
- VNC viewer) using "vncviewer -listen" and vncconnect(1) supported?
-
- As of Mar/2004 x11vnc supports reverse connections. On Unix one starts
- the VNC viewer in listen mode: "vncviewer -listen" (see your
- documentation for Windows, etc), and then starts up x11vnc with the
- -connect option. To connect immediately at x11vnc startup time use the
- "-connect host:port" option (use commas for a list of hosts to connect
- to.) The ":port" is optional (default is VNC listening port is 5500.)
-
- If a file is specified instead: -connect /path/to/some/file then that
- file is checked periodically (about once a second) for new hosts to
- connect to.
-
- The -remote control option (aka -R) can also be used to do this during
- an active x11vnc session, e.g.:
-x11vnc -display :0 -R connect:hostname.domain
-
- Use the "-connect_or_exit" option to have x11vnc exit if the reverse
- connection fails. Also, note the "-rfbport 0" option disables TCP
- listening for connections (potentially useful for reverse connection
- mode, assuming you do not want any "forward" connections.)
-
- Note that as of Mar/2006 x11vnc requires password authentication for
- reverse connections as well as for forward ones (assuming password
- auth has been enabled, e.g. via -rfbauth, -passwdfile, etc.) Many VNC
- servers do not require any password for reverse connections. To regain
- the old behavior supply this option "-env
- X11VNC_REVERSE_CONNECTION_NO_AUTH=1" to x11vnc.
-
- Vncconnect command: To use the vncconnect(1) program (from the core
- VNC package at www.realvnc.com) specify the -vncconnect option to
- x11vnc (Note: as of Dec/2004 -vncconnect is now the default.)
- vncconnect(1) must be pointed to the same X11 DISPLAY as x11vnc (since
- it uses X properties to communicate with x11vnc.) If you do not have
- or do not want to get the vncconnect(1) program, the following script
- (named "Vncconnect") may work if your xprop(1) supports the -set
- option:
-#!/bin/sh
-# usage: Vncconnect <host>
-# Vncconnect <host:port>
-# note: not all xprop(1) support -set.
-#
-xprop -root -f VNC_CONNECT 8s -set VNC_CONNECT "$1"
-
-
- Q-66: Can reverse connections be made to go through a Web or SOCKS
- proxy or SSH?
-
- Yes, as of Oct/2007 x11vnc supports reverse connections through
- proxies: use the "-proxy host:port" option. The default is to assume
- the proxy is a Web proxy. Note that most Web proxies only allow proxy
- destination connections to ports 443 (HTTPS) and 563 (SNEWS) and so
- this might not be too useful unless the proxy has been modified
- (AllowCONNECT apache setting) or the VNC viewer listens on one of
- those ports (or the router does a port redir.) A web proxy may also be
- specified via "-proxy http://host:port"
-
- For SOCKS4 and SOCKS4a proxies use this format "-proxy
- socks://host:port". If the reverse connection hostname is a numerical
- IP or "localhost" then SOCKS4 (no host lookup) is used, otherwise
- SOCKS4a will be used. For SOCKS5 (proxy will do lookup and many other
- things) use "-proxy socks5://host:port". Note that the SSH builtin
- SOCKS proxy "ssh -D port" only does SOCKS4 or SOCKS5, so use socks5://
- for a ssh -D proxy.
-
- The proxying works for both SSL encrypted and normal reverse
- connections.
-
- An experimental mode is "-proxy http://host:port/..." where the URL
- (e.g. a CGI script) is retrieved via the GET method. See -proxy for
- more info.
-
- Another experimental mode is "-proxy ssh://user@host" in which case a
- SSH tunnel is used for the proxying. See -proxy for more info.
-
- Up to 3 proxies may be chained together by listing them by commas
- e.g.: "-proxy http://host1:port1,socks5://host2:port2" in case one
- needs to ricochet off of several machines to ultimately reach the
- listening viewer.
-
-
- Q-67: Can x11vnc provide a multi-user desktop web login service as an
- Apache CGI or PHP script?
- Yes. See the example script desktop.cgi for ideas. It is in the source
- tree in the directory x11vnc/misc. It serves x11vnc's SSL enabled Java
- Applet to the web browser with the correct connection information for
- the user's virtual desktop (an Xvfb session via -create; be sure to
- add the Xvfb package.) HTTPS/SSL enabled Apache should be used to
- serve the script to avoid unix and vnc passwords from being sent in
- cleartext and sniffed.
-
- By default it uses a separate VNC port for each user desktop (either
- by autoprobing in a range of ports or using a port based on the userid
- number.) The web server's firewall must allow incoming connections to
- these ports.
-
- It is somewhat difficult to do all of this with x11vnc listening on a
- single port, however there is also a 'fixed port' scheme described in
- the script based on -loopbg that works fairly well (but more
- experience is needed to see what problems contention for the same port
- causes; however at worst one user may need to re-login.)
-
- There is also an optional 'port redirection' mode for desktop.cgi that
- allows redirection to other machines inside the firewall already
- running SSL enabled VNC servers. This provides much of the
- functionality as the SSL Portal and is easier to set up.
-
-
- Q-68: Can I use x11vnc as a replacement for Xvnc? (i.e. not for a real
- display, but for a virtual one I keep around.)
-
- You can, but you would not be doing this for performance reasons (for
- virtual X sessions via VNC, Xvnc should give the fastest response.)
- You may want to do this because Xvnc is buggy and crashes, does not
- support an X server extension you desire, or you want to take
- advantage of one of x11vnc's unending number of options and features.
-
- One way to achieve this is to have a Xvfb(1) virtual framebuffer X
- server running in the background and have x11vnc attached to it.
- Another method, faster and more accurate, is to use the "dummy" Device
- Driver in XFree86/Xorg (see below.)
-
- For these virtual sessions you will need to install the Xvfb program
- (e.g. apt-get install xvfb) or our Xdummy program (see below.)
-
- In either case, one can view this desktop both remotely and also
- locally using vncviewer. Make sure vncviewer's "-encodings raw" is in
- effect for local viewing (compression seems to slow things down
- locally.) For local viewing you set up a "bare" window manager that
- just starts up vncviewer and nothing else (See how below.)
-
- Here is one way to start up Xvfb:
- xinit -- /usr/bin/Xvfb :1 -cc 4 -screen 0 1024x768x16
-
- This starts up a 16bpp virtual display. To export it via VNC use
- x11vnc -display :1 ...
-
- Then have the remote vncviewer attach to x11vnc's VNC display (e.g. :0
- which is port 5900.)
-
- The "-cc 4" Xvfb option is to force it to use a TrueColor visual
- instead of DirectColor (this works around a recent bug in the Xorg
- Xvfb server.)
-
- One good thing about Xvfb is that the virtual framebuffer exists in
- main memory (rather than in the video hardware), and so x11vnc can
- "screen scrape" it very efficiently (more than, say, 100X faster than
- normal video hardware.)
-
- Update Nov/2006: See the FINDCREATEDISPLAY discussion of the "-display
- WAIT:cmd=FINDDISPLAY" option where virtual (Xvfb or Xdummy, or even
- real ones by changing an option) X servers are started automatically
- for new users connecting. This provides a "desktop service" for the
- machine. You either get your real X session or your virtual
- (Xvfb/Xdummy) one whenever you connect to the machine (inetd(8) is a
- nice way to provide this service.) The -find, -create, -svc, and
- -xdmsvc aliases can also come in handy here.
-
- There are some annoyances WRT Xvfb however. The default keyboard
- mapping seems to be very poor. One should run x11vnc with -add_keysyms
- option to have keysyms added automatically. Also, to add the Shift_R
- and Control_R modifiers something like this is needed:
-#!/bin/sh
-xmodmap -e "keycode any = Shift_R"
-xmodmap -e "add Shift = Shift_L Shift_R"
-xmodmap -e "keycode any = Control_R"
-xmodmap -e "add Control = Control_L Control_R"
-xmodmap -e "keycode any = Alt_L"
-xmodmap -e "keycode any = Alt_R"
-xmodmap -e "keycode any = Meta_L"
-xmodmap -e "add Mod1 = Alt_L Alt_R Meta_L"
-
- (note: these are applied automatically in the FINDCREATEDISPLAY mode
- of x11vnc.) Perhaps the Xvfb options -xkbdb or -xkbmap could be used
- to get a better default keyboard mapping...
-
- Dummy Driver: A user points out a faster and more accurate method is
- to use the "dummy" Device Driver of XFree86/Xorg instead of Xvfb. He
- uses this to create a persistent and resizable desktop accessible from
- anywhere. In the Device Section of the config file set Driver "dummy".
- You may also need to set VideoRam NNN to be large enough to hold the
- framebuffer. The framebuffer is kept in main memory like Xvfb except
- that the server code is closely correlated with the real XFree86/Xorg
- Xserver unlike Xvfb.
-
- The main drawback to this method (besides requiring extra
- configuration and possibly root permission) is that it also does the
- Linux Virtual Console/Terminal (VC/VT) switching even though it does
- not need to (since it doesn't use a real framebuffer.) There are some
- "dual headed" (actually multi-headed/multi-user) patches to the X
- server that turn off the VT usage in the X server. Update: As of
- Jul/2005 we have an LD_PRELOAD script Xdummy that allows you to use a
- stock (i.e. unpatched) Xorg or XFree86 server with the "dummy" driver
- and not have any VT switching problems! An advantage of Xdummy over
- Xvfb is that Xdummy supports RANDR dynamic screen resizing.
-
- The standard way to start the "dummy" driver would be:
-startx -- :1 -config /etc/X11/xorg.conf.dummy
-
- where the file /etc/X11/xorg.conf.dummy has its Device Section
- modified as described above. To use the LD_PRELOAD wrapper script:
-startx -- /path/to/Xdummy :1
-
- An xdm(1) example is also provided.
-
- In general, one can use these sorts of schemes to use x11vnc to export
- other virtual X sessions, say Xnest or even Xvnc itself (useful for
- testing x11vnc.)
-
- Local access (VNC Server and VNC Viewer on the same machine): You use
- a VNC viewer to access the display remotely; to access your virtual X
- display locally (i.e. while sitting at the same machine it is running
- on) one can perhaps have something like this in their $HOME/.xinitrc
-#!/bin/sh
-x11vnc -display :5 -rfbport 5905 -bg
-vncviewer -geometry +0+0 -encodings raw -passwd $HOME/.vnc/passwd localhost:5
-
- The display numbers (VNC and X) will likely be different (you could
- also try -find), and you may not need the -passwd. Recent RealVNC
- viewers might be this:
-#!/bin/sh
-x11vnc -display :5 -rfbport 5905 -bg
-vncviewer -FullScreen -PreferredEncoding raw -passwd $HOME/.vnc/passwd localhos
-t:5
-
- This way a bare X server is run with no window manager or desktop; it
- simply runs only the VNC Viewer on the real X server. The Viewer then
- draws the virtual X session on to the real one. On your system it
- might not be $HOME/.xinitrc, but rather .xsession, .Xclients, or
- something else. You will need to figure out what it is for your system
- and configuration.
-
-
- XDM/GDM/KDM One-Shot X sessions: For the general replacement of Xvnc
- by Xvfb+x11vnc, one user describes a similar setup he created where
- the X sessions are one-shot's (destroyed after the vncviewer
- disconnects) and it uses the XDM/GDM/KDM login greeter here.
-
-
- Q-69: How can I use x11vnc on "headless" machines? Why might I want
- to?
-
- An interesting application of x11vnc is to let it export displays of
- "headless" machines. For example, you may have some lab or server
- machines with no keyboard, mouse, or monitor, but each one still has a
- video card. One can use x11vnc to provide a simple "desktop service"
- from these server machines.
-
- An X server can be started on the headless machine (sometimes this
- requires configuring the X server to not fail if it cannot detect a
- keyboard or mouse, see the next paragraph.) Then you can export that X
- display via x11vnc (e.g. see this FAQ) and access it from anywhere on
- the network via a VNC viewer.
-
- Some tips on getting X servers to start on machines without keyboard
- or mouse: For XFree86/Xorg the Option "AllowMouseOpenFail" "true"
- "ServerFlags" config file option is useful. On Solaris Xsun the
- +nkeyboard and +nmouse options are useful (put them in the server
- command line args in /etc/dt/config/Xservers.) There are patches
- available for Xsun at lease back to Solaris 8 that support this. See
- Xserver(1) for more info.
-
- Although this usage may sound strange it can be quite useful for a GUI
- (or other) testing or QA setups: the engineers do not need to walk to
- lab machines running different hardware, OS's, versions, etc (or have
- many different machines in their office.) They just connect to the
- various test machines over the network via VNC. The advantage to
- testing this way instead of using Xvnc or even Xvfb is that the test
- is done using the real X server, fonts, video hardware, etc. that will
- be used in the field.
-
- One can imagine a single server machine crammed with as many video
- cards as it can hold to provide multiple simultaneous access or
- testing on different kinds of video hardware.
-
- See also the FINDCREATEDISPLAY discussion of the "-display
- WAIT:cmd=FINDDISPLAY" option where virtual Xvfb or Xdummy, or real X
- servers are started automatically for new users connecting. The -find,
- -create, -svc, and -xdmsvc aliases can also come in handy here.
-
- [Resource Usage and Performance]
-
- Q-70: I have lots of memory, but why does x11vnc fail with shmget:
- No space left on device or Minor opcode of failed request: 1
- (X_ShmAttach)?
-
- It is not a matter of free memory, but rather free shared memory (shm)
- slots, also known as shm segments. This often occurs on a public
- Solaris machine using the default of only 100 slots. You (or the owner
- or root) can clean them out with ipcrm(1). x11vnc tries hard to
- release its slots, but it, and other programs, are not always able to
- (e.g. if kill -9'd.)
-
- Sometimes x11vnc will notice the problem with shm segments and tries
- to get by with fewer, only giving a warning like this:
- 19/03/2004 10:10:58 shmat(tile_row) failed.
- shmat: Too many open files
- 19/03/2004 10:10:58 error creating tile-row shm for len=4
- 19/03/2004 10:10:58 reverting to single_copytile mode
-
- Here is a shell script shm_clear to list and prompt for removal of
- your unattached shm segments (attached ones are skipped.) I use it
- while debugging x11vnc (I use "shm_clear -y" to assume "yes" for each
- prompt.) If x11vnc is regularly not cleaning up its shm segments,
- please contact me so we can work to improve the situation.
-
- Longer term, on Solaris you can put something like this in
- /etc/system:
- set shmsys:shminfo_shmmax = 0x2000000
- set shmsys:shminfo_shmmni = 0x1000
-
- to sweep the problem under the rug (4096 slots.) On Linux, examine
- /proc/sys/kernel/shmmni; you can modify the value by writing to that
- file.
-
- Things are even more tight on Solaris 8 and earlier, there is a
- default maximum number of shm segments per process of 6. The error is
- the X server (not x11vnc) being unable to attach to the segments, and
- looks something like this:
- 30/04/2004 14:04:26 Got connection from client 192.168.1.23
- 30/04/2004 14:04:26 other clients:
- X Error of failed request: BadAccess (attempt to access private resource den
-ied)
- Major opcode of failed request: 131 (MIT-SHM)
- Minor opcode of failed request: 1 (X_ShmAttach)
- Serial number of failed request: 14
- Current serial number in output stream: 17
-
- This tight limit on Solaris 8 can be increased via:
- set shmsys:shminfo_shmseg = 100
-
- in /etc/system. See the next paragraph for more workarounds.
-
- To minimize the number of shm segments used by x11vnc try using the
- -onetile option (corresponds to only 3 shm segments used, and adding
- -fs 1.0 knocks it down to 2.) If you are having much trouble with shm
- segments, consider disabling shm completely via the -noshm option.
- Performance will be somewhat degraded but when done over local machine
- sockets it should be acceptable (see an earlier question discussing
- -noshm.)
-
-
- Q-71: How can I make x11vnc use less system resources?
-
- The -nap (now on by default; use -nonap to disable) and "-wait n"
- (where n is the sleep between polls in milliseconds, the default is 30
- or so) option are good places to start. In addition, something like
- "-sb 15" will cause x11vnc to go into a deep-sleep mode after 15
- seconds of no activity (instead of the default 60.)
-
- Reducing the X server bits per pixel depth (e.g. to 16bpp or even
- 8bpp) will further decrease memory I/O and network I/O. The ShadowFB X
- server setting will make x11vnc's screen polling less severe. Using
- the -onetile option will use less memory and use fewer shared memory
- slots (add -fs 1.0 for one less slot.)
-
-
- Q-72: How can I make x11vnc use MORE system resources?
-
- You can try -threads (note this mode can be unstable and/or crash; and
- as of May/2008 is strongly discouraged, see the option description) or
- dial down the wait time (e.g. -wait 1) and possibly dial down -defer
- as well. Note that if you try to increase the "frame rate" too much
- you can bog down the server end with the extra work it needs to do
- compressing the framebuffer data, etc.
-
- That said, it is possible to "stream" video via x11vnc if the video
- window is small enough. E.g. a 256x192 xawtv TV capture window (using
- the x11vnc -id option) can be streamed over a LAN or wireless at a
- reasonable frame rate. If the graphics card's framebuffer read rate is
- faster than normal then the video window size and frame rate can be
- much higher. The use of TurboVNC and/or TurboJPEG can make the frame
- rate somewhat higher still (but most of this hinges on the graphics
- card's read rate.)
-
-
- Q-73: I use x11vnc over a slow link with high latency (e.g. dialup
- modem or broadband), is there anything I can do to speed things up?
-
- Some things you might want to experiment with (many of which will help
- performance on faster links as well):
-
- X server/session parameters:
- * Configure the X server bits per pixel to be 16bpp or even 8bpp.
- (reduces amount of data needed to be polled, compressed, and sent)
- * Use a smaller desktop size (e.g. 1024x768 instead of 1280x1024)
- * Make sure the desktop background is a solid color (the background
- is resent every time it is re-exposed.) Consider using the -solid
- [color] option to try to do this automatically.
- * Configure your window manager or desktop "theme" to not use fancy
- images, shading, and gradients for the window decorations, etc.
- Disable window animations, etc. Maybe your desktop has a "low
- bandwidth" theme you can easily switch into and out of. Also in
- Firefox disable eye-candy, e.g.: Edit -> Preferences -> Advanced
- -> Use Smooth Scrolling (deselect it.)
- * Avoid small scrolls of large windows using the Arrow keys or
- scrollbar. Try to use PageUp/PageDown instead. (not so much of a
- problem in x11vnc 0.7.2 if -scrollcopyrect is active and detecting
- scrolls for the application.)
- * If the -wireframe option is not available (earlier than x11vnc
- 0.7.2 or you have disabled it via -nowireframe) then Disable
- Opaque Moves and Resizes in the window manager/desktop.
- * However if -wireframe is active (on by default in x11vnc 0.7.2)
- then you should Enable Opaque Moves and Resizes in the window
- manager! This seems counter-intuitive, but because x11vnc detects
- the move/resize events early there is a huge speedup over a slow
- link when Opaque Moves and Resizes are enabled. (e.g. CopyRect
- encoding will be used.)
- * Turn off Anti-aliased fonts on your system, web browser, terminal
- windows, etc. AA fonts do not compress as well as traditional
- fonts (sometimes 10X less.)
- * On Firefox/Mozilla (and anything else) turn off "Smooth Scroll"
- animations. In Firefox put in the URL "about:config" and set
- general.smoothScroll to false.
- * On Xorg/XFree86 turn on the Shadow Framebuffer to speed up
- reading. (Option "ShadowFB" "true" in the Device section of
- /etc/X11/XF86Config) This disables 2D acceleration on the physical
- display and so may not be worth it (if you play games, etc), but
- could be of use in some situations. Note: If the network link is
- very slow, this speedup may not be noticed.
-
- VNC viewer parameters:
- * Use a TightVNC enabled viewer! (Actually, RealVNC 4.x viewer with
- ZRLE encoding is not too bad either; some claim it is faster.)
- * Make sure the tight (or zrle) encoding is being used (look at
- vncviewer and x11vnc outputs)
- * Request 8 bits per pixel using -bgr233 (up to 4X speedup over
- depth 24 TrueColor (32bpp), but colors will be off)
- * RealVNC 4.x viewer has some extremely low color modes (only 64 and
- even 8 colors.) SSVNC does too. The colors are poor, but it is
- usually noticeably faster than bgr233 (256 colors.)
- * Try increasing the TightVNC -compresslevel (compresses more on
- server side before sending, but uses more CPU)
- * Try reducing the TightVNC -quality (increases JPEG compression,
- but is lossy with painting artifacts)
- * Try other VNC encodings via -encodings (tight may be the fastest,
- but you should compare it to zrle and maybe some of the others)
- * On the machine where vncviewer is run, make sure Backing Store is
- enabled (Xorg/XFree86 disables it by default causing re-exposures
- of vncviewer to be very slow) Option "backingstore" in config
- file.
-
- x11vnc parameters:
- * Make sure the -wireframe option is active (it should be on by
- default) and you have Opaque Moves/Resizes Enabled in the window
- manager.
- * Make sure the -scrollcopyrect option is active (it should be on by
- default.) This detects scrolls in many (but not all) applications
- an applies the CopyRect encoding for a big speedup.
- * Enforce a solid background when VNC viewers are connected via
- -solid
- * Try x11vnc's client-side caching client-side caching scheme:
- -ncache
- * Specify -speeds modem to force the wireframe and scrollcopyrect
- heuristic parameters (and any future ones) to those of a dialup
- modem connection (or supply the rd,bw,lat numerical values that
- characterize your link.)
- * If wireframe and scrollcopyrect aren't working, try using the more
- drastic -nodragging (no screen updates when dragging mouse, but
- sometimes you miss visual feedback)
- * Set -fs 1.0 (disables fullscreen updates)
- * Try increasing -wait or -defer (reduces the maximum "frame rate",
- but won't help much for large screen changes)
- * Try the -progressive pixelheight mode with the block pixelheight
- 100 or so (delays sending vertical blocks since they may change
- while viewer is receiving earlier ones)
- * If you just want to watch one (simple) window use -id or -appshare
- (cuts down extraneous polling and updates, but can be buggy or
- insufficient)
- * Set -nosel (disables all clipboard selection exchange)
- * Use -nocursor and -nocursorpos (repainting the remote cursor
- position and shape takes resources and round trips)
- * On very slow links (e.g. <= 28.8) you may need to increase the
- -readtimeout n setting if it sometimes takes more than 20sec to
- paint the full screen, etc.
- * Do not use -fixscreen to automatically refresh the whole screen,
- tap three Alt_L's then the screen has painting errors (rare
- problem.)
-
-
- Example for the KDE desktop:
-
- Launch the "KDE Control Center" utility. Sometimes this is called
- "Personal Settings".
-
- Select "Desktop".
-
- Then Select "Window Behavior". In the "Moving" Tab set these:
- * YES - Display content in moving windows
- * YES - Display content in resizing windows
- * NO - Display window geometry when moving or resizing
- * NO - Animate minimize and restore
-
- In the "Translucency" Tab set:
- * NO - Use translucency/shadows
-
- Next hit "Back" and then select "Panels".
-
- In the "Appearance" Tab set:
- * NO - Enable icon mouseover effects
- * NO - Enable transparency
-
- Now go all the way back up to the top and Select "Appearance &
- Themes".
-
- Select "Background" and set:
- * YES - No picture
- * Colors: Single Color
-
- Select "Fonts" and disable anti-aliased fonts if you are bold enough.
-
- Select "Launch Feedback" and set:
- * Busy Cursor: No Busy Cursor
- * NO - Enable taskbar notification
-
- Select "Screen Saver" and set:
- * Screen Saver: Blank Screen
-
- Select "Style" and in the "Effects" Tab set:
- * NO - Enable GUI effects
-
-
- Example for the GNOME desktop:
- * TBD.
-
-
- Q-74: Does x11vnc support the X DAMAGE Xserver extension to find
- modified regions of the screen quickly and efficiently?
-
- Yes, as of Mar/2005 x11vnc will use the X DAMAGE extension by default
- if it is available on the display. This requires libXdamage to be
- available in the build environment as well (recent Linux distros and
- Solaris 10 have it.)
-
- The DAMAGE extension enables the X server to report changed regions of
- the screen back to x11vnc. So x11vnc doesn't have to guess where the
- changes are (by polling every pixel of the entire screen every 2-4
- seconds.) The use of X DAMAGE dramatically reduces the load when the
- screen is not changing very much (i.e. most of the time.) It also
- noticeably improves updates, especially for very small changed areas
- (e.g. clock ticking, cursor flashing, typing, etc.)
-
- Note that the DAMAGE extension does not speed up the actual reading of
- pixels from the video card framebuffer memory, by, say, mirroring them
- in main memory. So reading the fb is still painfully slow (e.g.
- 5MB/sec), and so even using X DAMAGE when large changes occur on the
- screen the bulk of the time is still spent retrieving them. Not ideal,
- but use of the ShadowFB XFree86/Xorg option speeds up the reading
- considerably (at the cost of h/w acceleration.)
-
- Unfortunately the current Xorg DAMAGE extension implementation can at
- times be overly conservative and report very large rectangles as
- "damaged" even though only a small portion of the pixels have actually
- been modified. This behavior is often the fault of the window manager
- (e.g. it redraws the entire, unseen, frame window underneath the
- application window when it gains focus), or the application itself
- (e.g. does large, unnecessary repaints.)
-
- To work around this deficiency, x11vnc currently only trusts small
- DAMAGE rectangles to contain real damage. The larger rectangles are
- only used as hints to focus the traditional scanline polling (i.e. if
- a scanline doesn't intersect a recent DAMAGE rectangle, the scan is
- skipped.) You can use the "-xd_area A" option to adjust the size of
- the trusted DAMAGE rectangles. The default is 20000 pixels (e.g. a
- 140x140 square, etc.) Use "-xd_area 0" to disable the cutoff and trust
- all DAMAGE rectangles.
-
- The option "-xd_mem f" may also be of use in tuning the algorithm. To
- disable using DAMAGE entirely use "-noxdamage".
-
-
- Q-75: My OpenGL application shows no screen updates unless I supply
- the -noxdamage option to x11vnc.
- One user reports in his environment (MythTV using the NVIDIA OpenGL
- drivers) he gets no updates after the initial screen is drawn unless
- he uses the "-noxdamage" option.
-
- This seems to be a bug in the X DAMAGE implementation of that driver.
- You may have to use -noxdamage as well. A way to autodetect this will
- be tried, probably the best it will do is automatically stop using X
- DAMAGE.
-
- A developer for MiniMyth reports that the 'alphapulse' tag of the
- theme G.A.N.T. can also cause problems, and should be avoided when
- using VNC.
-
- Update: see this FAQ too.
-
-
- Q-76: When I drag windows around with the mouse or scroll up and down
- things really bog down (unless I do the drag in a single, quick
- motion.) Is there anything to do to improve things?
-
- This problem is primarily due to slow hardware read rates from video
- cards: as you scroll or move a large window around the screen changes
- are much too rapid for x11vnc to keep up them (it can usually only
- read the video card at about 5-10 MB/sec, so it can take a good
- fraction of a second to read the changes induce from moving a large
- window, if this to be done a number of times in succession the window
- or scroll appears to "lurch" forward.) See the description in the
- -pointer_mode option for more info. The next bottleneck is compressing
- all of these changes and sending them out to connected viewers,
- however the VNC protocol is pretty much self-adapting with respect to
- that (updates are only packaged and sent when viewers ask for them.)
-
- As of Jan/2004 there are some improvements to libvncserver. The
- default should now be much better than before and dragging small
- windows around should no longer be a huge pain. If for some reason
- these changes make matters worse, you can go back to the old way via
- the "-pointer_mode 1" option.
-
- Also added was the -nodragging option that disables all screen updates
- while dragging with the mouse (i.e. mouse motion with a button held
- down.) This gives the snappiest response, but might be undesired in
- some circumstances when you want to see the visual feedback while
- dragging (e.g. menu traversal or text selection.)
-
- As of Dec/2004 the -pointer_mode n option was introduced. n=1 is the
- original mode, n=2 an improvement, etc.. See the -pointer_mode n help
- for more info.
-
- Also, in some circumstances the -threads option can improve response
- considerably. Be forewarned that if more than one vncviewer is
- connected at the same time then libvncserver may not be thread safe
- (try to get the viewers to use different VNC encodings, e.g. tight and
- ZRLE.) This option can be unstable and so as of Feb/2008 it is
- disabled by default. Set env. X11VNC_THREADED=1 to re-enable.
-
- As of Apr/2005 two new options (see the wireframe FAQ and
- scrollcopyrect FAQ below) provide schemes to sweep this problem under
- the rug for window moves or resizes and for some (but not all) window
- scrolls. These are the preferred way of avoiding the "lurching"
- problem, contact me if they are not working. Note on SuSE and some
- other distros the RECORD X extension used by scrollcopyrect is not
- enabled by default, turn it on in xorg.conf:
-Section "Module"
- ...
- Load "record"
- ...
-EndSection
-
-
- Q-77: Why not do something like wireframe animations to avoid the
- windows "lurching" when being moved or resized?
-
- Nice idea for a hack! As of Apr/2005 x11vnc by default will apply
- heuristics to try to guess if a window is being (opaquely) moved or
- resized. If such a change is detected framebuffer polling and updates
- will be suspended and only an animated "wireframe" (a rectangle
- outline drawn where the moved/resized window would be) is shown. When
- the window move/resize stops, it returns to normal processing: you
- should only see the window appear in the new position. This spares you
- from interacting with a "lurching" window between all of the
- intermediate steps. BTW the lurching is due to slow video card read
- rates (see here too.) A displacement, even a small one, of a large
- window requires a non-negligible amount of time, a good fraction of a
- second, to read in from the hardware framebuffer.
-
- Note that Opaque Moves/Resizes must be Enabled by your window manager
- for -wireframe to do any good.
-
- The mode is currently on by default because most people are afflicted
- with the problem. It can be disabled with the -nowireframe option (aka
- -nowf.) Why might one want to turn off the wireframing? Since x11vnc
- is merely guessing when windows are being moved/resized, it may guess
- poorly for your window-manager or desktop, or even for the way you
- move the pointer. If your window-manager or desktop already does its
- own wireframing then this mode is a waste of time and could do the
- wrong thing occasionally. There may be other reasons the new mode
- feels unnatural. If you have very expensive video hardware (SGI, well
- now even proprietary Xorg drivers are fast at reading) or are using an
- in-RAM video framebuffer (SunRay, ShadowFB, Xvfb), the read rate from
- that framebuffer may be very fast (100's of MB/sec) and so you don't
- really see much lurching (at least over a fast LAN): opaque moves look
- smooth in x11vnc. Note: ShadowFB is often turned on when you are using
- the vesafb or fbdev XFree86 video driver instead of a native one so
- you might be using it already and not know.
-
- The heuristics used to guess window motion or resizing are simple, but
- are not fool proof: x11vnc is sometimes tricked and so you'll
- occasionally see the lurching opaque move and rarely something even
- worse.
-
- First it assumes that the move/resize will occur with a mouse button
- pressed, held down and dragged (of course this is only mostly true.)
- Next it will only consider a window for wireframing if the mouse
- pointer is initially "close enough" to the edges of the window frame,
- e.g. you have grabbed the title bar or a resizer edge (this
- requirement can be disabled and it also not applied if a modifier key,
- e.g. Alt, is pressed.) If these are true, it will wait an amount of
- time to see if the window starts moving or resizing. If it does, it
- starts drawing the wireframe "outline" of where the window would be.
- When the mouse button is released, or a timeout occurs, it goes back
- to the standard mode to allow the actual framebuffer changes to
- propagate to the viewers.
-
- These parameters can be tweaked:
- * Color/Shade of the wireframe.
- * Linewidth of the outline frame.
- * Cutoff size of windows to not apply wireframing to.
- * Cutoffs for closeness to Top, Bottom, Left, and Right edges of
- window.
- * Modifier keys to enable interior window grabbing.
- * Maximum time to wait for dragging pointer events.
- * Maximum time to wait for the window to start moving/resizing.
- * Maximum time to show a wireframe animation.
- * Minimum time between sending wireframe outlines.
-
- See the "-wireframe tweaks" option for more details. On a slow link,
- e.g. dialup modem, the parameters may be automatically adjusted for
- better response.
-
-
- CopyRect encoding: In addition to the above there is the
- "-wirecopyrect mode" option. It is also on by default. This instructs
- x11vnc to not only show the wireframe animation, but to also instruct
- all connected VNC viewers to locally translate the window image data
- from the original position to the new position on the screen when the
- animation is done. This speedup is the VNC CopyRect encoding: the
- framebuffer update doesn't need to send the actual new image data.
- This is nice in general, and very convenient over a slow link, but
- since it is based on heuristics you may need to disable it with the
- -nowirecopyrect option (aka -nowcr) if it works incorrectly or
- unnaturally for you.
-
- The -wirecopyrect modes are: "never" (same as -nowirecopyrect); "top",
- only apply the CopyRect if the window is appears to be on the top of
- the window stack and is not obstructed by other windows; and "always"
- to always try to apply the CopyRect (obstructed regions are usually
- clipped off and not translated.)
-
- Note that some desktops (KDE and xfce) appear to mess with the window
- stacking in ways that are not yet clear. In these cases x11vnc works
- around the problem by applying the CopyRect even if obscuring windows'
- data is translated! Use -nowirecopyrect if this yields undesirable
- effects for your desktop.
-
- Also, the CopyRect encoding may give incorrect results under -scale
- (depending on the scale factor the CopyRect operation is often only
- approximate: the correctly scaled framebuffer will be slightly
- different from the translated one.) x11vnc will try to push a
- "cleanup" update after the CopyRect if -scale is in effect. Use
- -nowirecopyrect if this or other painting errors are unacceptable.
-
-
- Q-78: Can x11vnc try to apply heuristics to detect when a window is
- scrolling its contents and use the CopyRect encoding for a speedup?
-
- Another nice idea for a hack! As of May/2005 x11vnc will by default
- apply heuristics to try to detect if the window that has the input
- focus is scrolling its contents (but only when x11vnc is feeding user
- input, keystroke or pointer, to the X server.) So, when detected,
- scrolls induced by dragging on a scrollbar or by typing (e.g. Up or
- Down arrows, hitting Return in a terminal window, etc), will show up
- much more quickly than via the standard x11vnc screen polling update
- mechanism.
-
- There will be a speedup for both slow and fast links to viewers. For
- slow links the speedup is mostly due to the CopyRect encoding not
- requiring the image data to be transmitted over the network. For fast
- links the speedup is primarily due to x11vnc not having to read the
- scrolled framebuffer data from the X server (recall that reading from
- the hardware framebuffer is slow.)
-
- To do this x11vnc uses the RECORD X extension to snoop the X11
- protocol between the X client with the focus window and the X server.
- This extension is usually present on most X servers (but SuSE disables
- it for some reason.) On XFree86/Xorg it can be enabled via Load
- "record" in the Module section of the config file if it isn't already:
-Section "Module"
- ...
- Load "record"
- ...
-EndSection
-
- Currently the RECORD extension is used as little as possible so as to
- not slow down regular use. Only simple heuristics are applied to
- detect XCopyArea and XConfigureWindow calls from the application.
- These catch a lot of scrolls, e.g. in mozilla/firefox and in terminal
- windows like gnome-terminal and xterm. Unfortunately the toolkits KDE
- applications use make scroll detection less effective (only rarely are
- they detected: i.e. Konqueror and Konsole don't work.) An interesting
- project, that may be the direction x11vnc takes, is to record all of
- the X11 protocol from all clients and try to "tee" the stream into a
- modified Xvfb watching for CopyRect and other VNC speedups. A
- potential issue is the RECORD stream is delayed from actual view on
- the X server display: if one falls too far behind it could become a
- mess...
-
- The initial implementation of -scrollcopyrect option is useful in that
- it detects many scrolls and thus gives a much nicer working
- environment (especially when combined with the -wireframe
- -wirecopyrect options, which are also on by default; and if you are
- willing to enable the ShadowFB things are very fast.) The fact that
- there aren't long delays or lurches during scrolling is the primary
- improvement.
-
- But there are some drawbacks:
- * Not all scrolls are detected. Some apps scroll windows in ways
- that cannot currently be detected, and other times x11vnc "misses"
- the scroll due to timeouts, etc. Sometimes it is more distracting
- that a speedup occasionally doesn't work as opposed to being
- consistently slow!
- * For rapid scrolling (i.e. sequence of many scrolls over a short
- period) there can be painting errors (tearing, bunching up, etc.)
- during the scroll. These will repair themselves after the scroll
- is over, but when they are severe it can be distracting. Try to
- think of the approximate window contents as a quicker and more
- useful "animation" compared to the slower polling scheme...
- * Scrolling inside shells in terminal windows (gnome-terminal,
- xterm), can lead to odd painting errors. This is because x11vnc
- did not have time to detect a screen change just before the scroll
- (most common is the terminal undraws the block cursor before
- scrolling the text up: in the viewer you temporarily see multiple
- block cursors.) Another issue is with things like more(1): scroll
- detection for 5-6 lines happens nicely, but then it can't keep up
- and so there is a long pause for the standard polling method to
- deliver the remaining updates.
- * More rarely sometimes painting errors are not repaired after the
- scroll is over. This may be a bug in x11vnc or libvncserver, or it
- may be an inescapable fact of the CopyRect encoding and the delay
- between RECORD callbacks and what is actually on the X display.
- One can tap the Alt_L key (Left "Alt" key) 3 times in a row to
- signal x11vnc to refresh the screen to all viewers. Your
- VNC-viewer may have its own screen refresh hot-key or button. See
- also: -fixscreen
- * Some applications, notably OpenOffice, do XCopyArea scrolls in
- weird ways that assume ancestor window clipping is taking place.
- See the -scr_skip option for ways to tweak this on a
- per-application basis.
- * Selecting text while dragging the mouse may be slower, especially
- if the Button-down event happens near the window's edge. This is
- because the scrollcopyrect scheme is watching for scrolls via
- RECORD and has to wait for a timeout to occur before it does the
- update.
- * For reasons not yet understood the RECORD extension can stop
- responding (and hence scrolls are missed.) As a workaround x11vnc
- attempts to reset the RECORD connection every 60 seconds or so.
- Another workaround is to type 4 Super_L (Left Super/Windows-Flag
- key) in a row to reset RECORD. Work is in progress to try to fix
- this bug.
- * Sometimes you need to "retrain" x11vnc for a certain window
- because it fails to detect scrolls in it. Sometimes clicking
- inside the application window or selecting some text in it to
- force the focus helps.
- * When using the -scale option there will be a quick CopyRect
- scroll, but it needs to be followed by a slower "cleanup" update.
- This is because for a fixed finite screen resolution (e.g. 75 dpi)
- scaling and copyrect-ing are not exactly independent. Scaling
- involves a blending of nearby pixels and if you translate a pixel
- the neighbor pixel weighting may be different. So you have to wait
- a bit for the cleanup update to finish. On slow links x11vnc may
- automatically decide to not detect scrolls when -scale is in
- effect. In general it will also try to defer the cleanup update if
- possible.
-
- If you find the -scrollcopyrect behavior too approximate or
- distracting you can go back to the standard polling-only update method
- with the -noscrollcopyrect (or -noscr for short.) If you find some
- extremely bad and repeatable behavior for -scrollcopyrect please
- report a bug.
-
- Alternatively, as with -wireframe, there are many tuning parameters to
- try to improve the situation. You can also access these parameters
- inside the gui under "Tuning". These parameters can be tweaked:
- * The minimum pixel area of a rectangle to be watched for scrolls.
- * A list if application names to skip scroll detection.
- * Which keystrokes should trigger scroll detection.
- * Which applications should have a "terminal" tweak applied to them.
- * When repeating keys (e.g. Up arrow) should be discarded to
- preserve a scroll.
- * Cutoffs for closeness to Top, Bottom, Left, and Right edges of
- window for mouse induced scrolls.
- * Set timeout parameters for keystroke induced scrolls.
- * Set timeout parameters for mouse pointer induced scrolls.
- * Have the full screen be periodically refreshed to fix painting
- errors.
-
-
- Q-79: Can x11vnc do client-side caching of pixel data? I.e. so when
- that pixel data is needed again it does not have to be retransmitted
- over the network.
-
- As of Dec/2006 in the 0.9 development tarball there is an experimental
- client-side caching implementation enabled by the "-ncache n" option.
- In fact, during the test period it was on by default with n set to 10.
- To disable it use "-noncache".
-
- It is a simple scheme where a (very large) lower portion of the
- framebuffer (i.e. starting just below the user's actual desktop
- display) is used for storing pixel data. CopyRect; a fast, essentially
- local viewer-side VNC encoding; is used to swap the pixel data in and
- out of the actual display area. It gives an excellent speedup for
- iconifying/deiconifying and moving windows and re-posting of menus
- (often it doesn't feel like VNC at all: there is no delay waiting for
- the pixel data to fill in.)
-
- This scheme is nice because it does all of this within the existing
- VNC protocol, and so it works with all VNC viewers.
-
- A challenge to doing more sophisticated (e.g. compressed and/or
- shared) client-side caching is that one needs to extend the VNC
- protocol, modify a viewer and then also convince users to adopt your
- modified VNC Viewer (or get the new features to be folded into the
- main VNC viewers, patches accepted, etc... likely takes many years
- before they might be deployed in the field.) So it is convenient that
- the "-ncache n" works with any unaltered VNC viewer.
-
- A drawback of the "-ncache n" method is that in the VNC Viewer you can
- scroll down and actually see the cached pixel data. So it looks like
- there is a bug: you can scroll down in your viewer and see a strange
- "history" of windows on your desktop. This is working as intended. One
- will need to try to adjust the size of his VNC Viewer window so the
- cache area cannot be seen. SSVNC (see below) can do this
- automatically.
-
- At some point LibVNCServer may implement a "rfbFBCrop" pseudoencoding
- that viewers can use to learn which portion of the framebuffer to
- actually show to the users (with the hidden part used for caching, or
- perhaps something else, maybe double buffering or other offscreen
- rendering...)
-
- The Enhanced TightVNC Viewer (SSVNC) Unix viewer has a nice -ycrop
- option to help hide the pixel cache area from view. It will turn on
- automatically if the framebuffer appears to be very tall (height more
- than twice the width), or you can supply the actual value for the
- height. If the screen is resized by scaling, etc, the ycrop value is
- scaled as well. In fullscreen mode you cannot scroll past the end of
- the actual screen, and in non-fullscreen mode the window manager frame
- is adjusted to fit the actual display (so you don't see the pixel
- cache region) and the scrollbars are very thin to avoid distraction
- and trouble fitting inside your display. Use the "-sbwidth n" viewer
- option to make the scrollbars thicker if you like.
-
- Another drawback of the scheme is that it is VERY memory intensive,
- the n in "-ncache n" is the factor of increase over the base
- framebuffer size to use for caching. It is an even integer and should
- be fairly large, 6-12, to achieve good response. This usually requires
- about 50-100MB of additional RAM on both the client and server sides.
- For example with n=6 a 1280x1024 display will use a framebuffer that
- is 1280x7168: everything below row 1024 is the pixel buffer cache. If
- you are running on low memory machines or memory is tight because of
- other running applications you should not use -ncache.
-
- The reason for so much memory is because the pixel data is not
- compressed and so the whole window to be saved must be stored
- "offscreen". E.g. for a large web browser window this can be nearly 1
- million pixels, and that is only for a single window! One typically
- wants to cycle between 5-10 large active windows. Also because both
- backing-store (the window's actual contents) and save-unders (the
- pixels covered up by the window) are cached offscreen that introduces
- an additional factor of 2 in memory use.
-
- However, even in the smallest usage mode with n equal 2 and
- -ncache_no_rootpixmap set (this requires only 2X additional
- framebuffer memory) there is still a noticable improvement for many
- activities, although it is not as dramatic as with, say n equal 12 and
- rootpixmap (desktop background) caching enabled.
-
- The large memory consumption of the current implementation can be
- thought of as a tradeoff to providing caching and being compatible
- with all VNC viewers and also ease of implementing. Hopefully it can
- be tuned to use less, or the VNC community will extend the protocol to
- allow caching and replaying of compressed blobs of data.
-
- Another option to experiment with is "-ncache_cr". By specifying it,
- x11vnc will try to do smooth opaque window moves instead of its
- wireframe. This can give a very nice effect (note: on Unix the realvnc
- viewer seems to be smoother than the tightvnc viewer), but can lead to
- some painting problems, and can be jerky in some circumstances.
-
- Surprisingly, for very slow connections, e.g. modem, the -ncache_cr
- option can actually improve window drags. This is probably because no
- pixel data (only CopyRect instructions) are sent when dragging a
- window. Normally, the wireframe must be sent and this involves
- compressing and sending the lines that give rise to the moving box
- effect (note that real framebuffer data is sent to "erase" the white
- lines of the box.)
-
- If you experience painting errors you can can tap the Alt_L key (Left
- "Alt" key) 3 times in a row to signal x11vnc to refresh the screen to
- all viewers. You may also need to iconify and then deiconify any
- damaged windows to correct their cache data as well. Note that if you
- change color viewer depth (e.g. 8bpp to full color) dynamically that
- will usually lead to the entire extended framebuffer being resent
- which can take a long time over very slow links: it may be better to
- reconnect and reset the format right after doing so. x11vnc will try
- to detect the format change and clear (make completely black) the
- cache region.
-
- Gotcha for older Unix VNC Viewers: The older Unix VNC viewers (e.g.
- current TightVNC Unix Viewer) require X server backingstore to keep
- off-viewer screen data local. If the viewer-side X server has
- backingstore disabled (sadly, currently the default on Linux, etc),
- then to get the offscreen pixels the viewer has to ask for a refresh
- over the network, thereby defeating the caching. Use something like
- this in your viewer-side /etc/X11/xorg.conf file (or otherwise get
- your viewer-side system to do it)
-Section "Device"
- ...
- Option "backingstore"
- ...
-EndSection
-
- No problems like this have been observed with Windows VNC Viewers:
- they all seem to keep their entire framebuffer in local memory.
-
- Gotcha for KDE krdc VNC Viewer: One user found that KDE's krdc viewer
- has some sort of hardwired limit on the maximum size of the
- framebuffer (64MB?). It fails quickly saying "The connection to the
- host has been interrupted." The workaround for his 1280x1024
- x11vnc-side display was to run with "-ncache 10", i.e. a smaller value
- to be under the krdc threshold.
-
- Although this scheme is not as quick (nor as compressed) as
- nx/nomachine, say, it does provide a good step in the direction of
- improving VNC performance by client side caching.
-
-
- Q-80: Does x11vnc support TurboVNC?
-
- As of Feb/2009 (development tarball) there is an experimental kludge
- to let you build x11vnc using TurboVNC's modified TightVNC encoding.
- TurboVNC is part of the VirtualGL project. It does two main things to
- speed up the TightVNC encoding:
- * It eliminates bottlenecks, overheads, wait-times in the TightVNC
- encoding implementation and instead only worries about sending
- very well (and quickly) compressed JPEG data.
- * A fast proprietary JPEG implemention is used (Intel IPP on x86)
- instead of the usual libjpeg implementation. TurboJPEG is an
- interface library, libturbojpeg, provided by the project that
- achieves this.
-
- TurboVNC works very well over LAN and evidently fast Broadband too.
- When using it with x11vnc in such a situation you may want to dial
- down the delays, e.g. "-wait 5" and "-defer 5" (or even a smaller
- setting) to poll and pump things out more quickly.
-
- See the instructions in "x11vnc/misc/turbovnc/README" for how to build
- x11vnc with TurboVNC support. You will also need to download the
- TurboJPEG software.
-
- In brief, the steps look like this:
- cd x11vnc-x.y.z/x11vnc/misc/turbovnc
- ./apply_turbovnc
- cd ../../..
- env LDFLAGS='-L/DIR -Xlinker --rpath=/DIR' ./configure
- make AM_LDFLAGS='-lturbojpeg'
-
- where you replace "/DIR" with the directory containing libturbojpeg.so
- you downloaded separately. If it works out well enough TurboVNC
- support will be integrated into x11vnc and more of its tuning features
- will be implemented. Support for TurboVNC in SSVNC viewer has been
- added as an experiment as well. If you try either one, let us know how
- it went.
-
- There also may be some Linux.i686 and Darwin.i386 x11vnc binaries with
- TurboVNC support in the misc. bins directory. For other platforms you
- will need to compile yourself.
-
- On relatively cheap and old hardware (Althon64 X2 5000+ / GeForce
- 6200) x11vnc and SSVNC, both TurboVNC enabled, were able to sustain
- 13.5 frames/sec (fps) and 15 Megapixels/sec using the VirtualGL
- supplied OpenGL benchmark program glxspheres. VirtualGL on higher-end
- hardware can sustain 20-30 fps with the glxspheres benchmark.
-
- Potential Slowdown: As we describe elsewhere, unless you use x11vnc
- with an X server using, say, NVidia proprietary drivers (or a virtual
- X server like Xvfb or Xdummy, or in ShadowFB mode), then the read rate
- from the graphics card can be rather slow (e.g. 10 MB/sec) and becomes
- the bottleneck when using x11vnc over fast networks. Note that all of
- Xorg's drivers currently (2009) have slow read rates (only proprietary
- drivers appear to have optimized reads.)
-
- So under these (more or less typical) conditions, the speed
- improvement provided by TurboVNC may only be marginal. Look for this
- output to see your read rate:
- 28/02/2009 11:11:07 Autoprobing TCP port
- 28/02/2009 11:11:07 Autoprobing selected port 5900
- 28/02/2009 11:11:08 fb read rate: 10 MB/sec
- 28/02/2009 11:11:08 screen setup finished.
-
- A rate of 10 MB/sec means a 1280x1024x24 screen takes 0.5 seconds to
- read in. TurboVNC compresses that to JPEG in a much shorter time. On
- the other hand, an NVidia driver may have a read rate of 250 MB/sec
- and so only takes 0.02 seconds to read the entire screen in.
-
-
-
- [Mouse Cursor Shapes]
-
- Q-81: Why isn't the mouse cursor shape (the little icon shape where
- the mouse pointer is) correct as I move from window to window?
-
- On X servers supporting XFIXES or Solaris/IRIX Overlay extensions it
- is possible for x11vnc to do this correctly. See a few paragraphs down
- for the answer.
-
- Historically, the X11 mouse cursor shape (i.e. little picture: an
- arrow, X, I-beam, resizer, etc) is one of the few WRITE-only objects
- in X11. That is, an application can tell the X server what the cursor
- shape should be when the pointer is in a given window, but a program
- (like x11vnc) unfortunately cannot read this information. I believe
- this is because the cursor shape is often downloaded to the graphics
- hardware (video card), but I could be mistaken.
-
- A simple kludge is provided by the "-cursor X" option that changes the
- cursor when the mouse is on the root background (or any window has the
- same cursor as the root background.) Note that desktops like GNOME or
- KDE often cover up the root background, so this won't work for those
- cases. Also see the "-cursor some" option for additional kludges.
-
- Note that as of Aug/2004 on Solaris using the SUN_OVL overlay
- extension and IRIX, x11vnc can show the correct mouse cursor when the
- -overlay option is supplied. See this FAQ for more info.
-
- Also as of Dec/2004 XFIXES X extension support has been added to allow
- exact extraction of the mouse cursor shape. XFIXES fixes the problem
- of the cursor-shape being write-only: x11vnc can now query the X
- server for the current shape and send it back to the connected
- viewers. XFIXES is available on recent Linux Xorg based distros and
- Solaris 10.
-
- The only XFIXES issue is the handling of alpha channel transparency in
- cursors. If a cursor has any translucency then in general it must be
- approximated to opaque RGB values for use in VNC. There are some
- situations where the cursor transparency can also handled exactly:
- when the VNC Viewer requires the cursor shape be drawn into the VNC
- framebuffer or if you apply a patch to your VNC Viewer to extract
- hidden alpha channel data under 32bpp. Details can be found here.
-
-
- Q-82: When using XFIXES cursorshape mode, some of the cursors look
- really bad with extra black borders around the cursor and other cruft.
- How can I improve their appearance?
-
- This happens for cursors with transparency ("alpha channel"); regular
- X cursors (bitmaps) should be correct. Unfortunately x11vnc 0.7 was
- released with a very poor algorithm for approximating the
- transparency, which led to the ugly black borders.
-
- The problem is as follows: XFIXES allows x11vnc to retrieve the
- current X server cursor shape, including the alpha channel for
- transparency. For traditional bitmap cursors the alpha value will be 0
- for completely transparent pixels and 255 for completely opaque
- pixels; whereas for modern, eye-candy cursors an alpha value between 0
- and 255 means to blend in the background colors to that degree with
- the cursor colors. The pixel color blending formula is something like
- this: Red = Red_cursor * a + Red_background * (1 - a), (where here 0
- =< a =< 1), with similar for Green and Blue. The VNC protocol does not
- currently support an alpha channel in cursors: it only supports
- regular X bitmap cursors and Rich Cursors that have RGB (Red, Green,
- Blue) color data, but no "A" = alpha data. So in general x11vnc has to
- approximate a cursor with transparency to create a Rich Cursor. This
- is easier said than done: some cursor themes have cursors with
- complicated drop shadows and other forms of translucency.
-
- Anyway, for the x11vnc 0.7.1 release the algorithm for approximating
- transparency is much improved and hopefully gives decent cursor shapes
- for most cursor themes and you don't have to worry about it.
-
- In case it still looks bad for your cursor theme, there are (of
- course!) some tunable parameters. The "-alphacut n" option lets you
- set the threshold "n" (between 0 and 255): cursor pixels with alpha
- values below n will be considered completely transparent while values
- equal to or above n will be completely opaque. The default is 240. The
- "-alphafrac f" option tries to correct individual cursors that did not
- fare well with the default -alphacut value: if a cursor has less than
- fraction f (between 0.0 and 1.0) of its pixels selected by the default
- -alphacut, the threshold is lowered until f of its pixels are
- selected. The default fraction is 0.33.
-
- Finally, there is an option -alpharemove that is useful for themes
- where many cursors are light colored (e.g. "whiteglass".) XFIXES
- returns the cursor data with the RGB values pre-multiplied by the
- alpha value. If the white cursors look too grey, specify -alpharemove
- to brighten them by having x11vnc divide out the alpha value.
-
- One user played with these parameters and reported back:
- Of the cursor themes present on my system:
-
- gentoo and gentoo-blue: alphacut:192 - noalpharemove
-
- gentoo-silver: alphacut:127 and alpharemove
-
- whiteglass and redglass (presumably also handhelds, which is based
- heavily on redglass) look fine with the apparent default of alphacut:255.
-
-
- Q-83: In XFIXES mode, are there any hacks to handle cursor
- transparency ("alpha channel") exactly?
-
- As of Jan/2005 libvncserver has been modified to allow an alpha
- channel (i.e. RGBA data) for Rich Cursors. So x11vnc can now send the
- alpha channel data to libvncserver. However, this data will only be
- used for VNC clients that do not support the CursorShapeUpdates VNC
- extension (or have disabled it.) It can be disabled for all clients
- with the -nocursorshape x11vnc option. In this case the cursor is
- drawn, correctly blended with the background, into the VNC framebuffer
- before being sent out to the client. So the alpha blending is done on
- the x11vnc side. Use the -noalphablend option to disable this behavior
- (always approximate transparent cursors with opaque RGB values.)
-
- The CursorShapeUpdates VNC extension complicates matters because the
- cursor shape is sent to the VNC viewers supporting it, and the viewers
- draw the cursor locally. This improves response over slow links. Alpha
- channel data for these locally drawn cursors is not supported by the
- VNC protocol.
-
- However, in the libvncserver CVS there is a patch to the TightVNC
- viewer to make this work for CursorShapeUpdates under some
- circumstances. This hack is outside of the VNC protocol. It requires
- the screens on both sides to be depth 24 at 32bpp (it uses the extra 8
- bits to secretly hide the cursor alpha channel data.) Not only does it
- require depth 24 at 32bpp, but it also currently requires the client
- and server to be of the same endianness (otherwise the hidden alpha
- data gets reset to zero by a libvncserver translation function; we can
- fix this at some point if there is interest.) The patch is for the
- TightVNC 1.3dev5 Unix vncviewer and it enables the TightVNC viewer to
- do the cursor alpha blending locally. The patch code should give an
- example on how to change the Windows TightVNC viewer to achieve the
- same thing (send me the patch if you get that working.)
-
- This patch is applied to the Enhanced TightVNC Viewer (SSVNC) package
- we provide.
-
- [Mouse Pointer]
-
- Q-84: Why does the mouse arrow just stay in one corner in my
- vncviewer, whereas my cursor (that does move) is just a dot?
-
- This default takes advantage of a tightvnc extension
- (CursorShapeUpdates) that allows specifying a cursor image shape for
- the local VNC viewer. You may disable it with the -nocursor option to
- x11vnc if your viewer does not have this extension.
-
- Note: as of Aug/2004 this should be fixed: the default for
- non-tightvnc viewers (or ones that do not support CursorShapeUpdates)
- will be to draw the moving cursor into the x11vnc framebuffer. This
- can also be disabled via -nocursor.
-
-
- Q-85: Can I take advantage of the TightVNC extension to the VNC
- protocol where Cursor Positions Updates are sent back to all connected
- clients (i.e. passive viewers can see the mouse cursor being moved
- around by another viewer)?
-
- Use the -cursorpos option when starting x11vnc. A VNC viewer must
- support the Cursor Positions Updates for the user to see the mouse
- motions (the TightVNC viewers support this.) As of Aug/2004 -cursorpos
- is the default. See also -nocursorpos and -nocursorshape.
-
-
- Q-86: Is it possible to swap the mouse buttons (e.g. left-handed
- operation), or arbitrarily remap them? How about mapping button clicks
- to keystrokes, e.g. to partially emulate Mouse wheel scrolling?
-
- You can remap the mouse buttons via something like: -buttonmap 13-31
- (or perhaps 12-21.) Also, note that xmodmap(1) lets you directly
- adjust the X server's button mappings, but in some circumstances it
- might be more desirable to have x11vnc do it.
-
- One user had an X server with only one mouse button(!) and was able to
- map all of the VNC client mouse buttons to it via: -buttonmap 123-111.
-
- Note that the -debug_pointer option prints out much info for every
- mouse/pointer event and is handy in solving problems.
-
- To map mouse button clicks to keystrokes you can use the alternate
- format where the keystrokes are enclosed between colons like this
- :<KeySym>: in place of the mouse button digit. For a sequence of
- keysyms separate them with "+" signs. Look in the include file
- <X11/keysymdef.h>, or use xev(1), or -debug_keyboard to find the
- keysym names. Button clicks can also be included in the sequence via
- the fake keysyms Button1, etc.
-
- As an example, suppose the VNC viewer machine has a mouse wheel (these
- generate button 4 and 5 events), but the machine that x11vnc is run on
- only has the 3 regular buttons. In normal operation x11vnc will
- discard the button 4 and 5 events. However, either of the following
- button maps could possibly be of use emulating the mouse wheel events
- in this case:
- -buttonmap 12345-123:Prior::Next:
- -buttonmap 12345-123:Up+Up+Up::Down+Down+Down:
-
- Exactly what keystroke "scrolling" events they should be bound to
- depends on one's taste. If this method is too approximate, one could
- consider not using -buttonmap but rather configuring the X server to
- think it has a mouse with 5 buttons even though the physical mouse
- does not. (e.g. 'Option "ZAxisMapping" "4 5"'.)
-
- Note that when a keysym-mapped mouse button is clicked down this
- immediately generates the key-press and key-release events (for each
- keysym in turn if the mapping has a sequence of keysyms.) When the
- mouse button goes back up nothing is generated.
-
- If you include modifier keys like Shift_L instead of key-press
- immediately followed by key-release the state of the modifier key is
- toggled (however the initial state of the modifier key is ignored.) So
- to map the right button to type my name 'Karl Runge' I could use this:
- -buttonmap 3-:Shift_L+k+Shift_L+a+r+l+space+Shift_L+r+Shift_L+u+n+g+e:
-
- (yes, this is getting a little silly.)
-
- BTW, Coming the other way around, if the machine you are sitting at
- does not have a mouse wheel, but the remote machine does (or at least
- has 5 buttons configured), this key remapping can be useful:
- -remap Super_R-Button4,Menu-Button5
-
- you just tap those two keys to get the mouse wheel scrolls (this is
- more useful than the Up and Down arrow keys because a mouse wheel
- "click" usually gives a multi-line scroll.)
- [Keyboard Issues]
-
- Q-87: How can I get my AltGr and Shift modifiers to work between
- keyboards for different languages?
-
- The option -modtweak should help here. It is a mode that monitors the
- state of the Shift and AltGr Modifiers and tries to deduce the correct
- keycode to send, possibly by sending fake modifier key presses and
- releases in addition to the actual keystroke.
-
- Update: As of Jul/2004 -modtweak is now the default (use -nomodtweak
- to get the old behavior.) This was done because it was noticed on
- newer XFree86 setups even on bland "us" keyboards like "pc104 us"
- XFree86 included a "ghost" key with both "<" and ">" it. This key does
- not exist on the keyboard (see this FAQ for more info.) Without
- -modtweak there was then an ambiguity in the reverse map keysym =>
- keycode, making it so the "<" symbol could not be typed.
-
- Also see the FAQ about the -xkb option for a more powerful method of
- modifier tweaking for use on X servers with the XKEYBOARD extension.
-
- When trying to resolve keyboard mapping problems, note that the
- -debug_keyboard option prints out much info for every keystroke and so
- can be useful debugging things.
-
- Note that one user had a strange setup and none of the above helped.
- His solution was to disable all of the above and use -nomodtweak. This
- is the simplest form of keystroke insertion and it actually solved the
- problem. Try it if the other options don't help.
-
-
- Q-88: When I try to type a "<" (i.e. less than) instead I get ">"
- (i.e. greater than)! Strangely, typing ">" works OK!!
-
- Does your keyboard have a single key with both "<" and ">" on it? Even
- if it doesn't, your X server may think your keyboard has such a key
- (e.g. pc105 in the XF86Config file when it should be something else,
- say pc104.)
-
- Short Cut: Try the -xkb or -sloppy_keys options and see if that helps
- the situation. The discussion below is a bit outdated (e.g. -modtweak
- is now the default) but it is useful reference for various tricks and
- so is kept.
-
-
- The problem here is that on the Xserver where x11vnc is run there are
- two keycodes that correspond to the "<" keysym. Run something like
- this to see:
-
- xmodmap -pk | egrep -i 'KeyCode|less|greater'
- There are 4 KeySyms per KeyCode; KeyCodes range from 8 to 255.
- KeyCode Keysym (Keysym) ...
- 59 0x002c (comma) 0x003c (less)
- 60 0x002e (period) 0x003e (greater)
- 94 0x003c (less) 0x003e (greater)
-
- That keycode 94 is the special key with both "<" and ">". When x11vnc
- receives the "<" keysym over the wire from the remote VNC client, it
- unfortunately maps it to keycode 94 instead of 59, and sends 94 to the
- X server. Since Shift is down (i.e. you are Shifting the comma key),
- the X server interprets this as Shifted-94, which is ">".
-
- A workaround in the X server configuration is to "deaden" that special
- key:
-
- xmodmap -e "keycode 94 = "
-
- However, one user said he had to do this:
-
- xmodmap -e "keycode 94 = 0x002c 0x003c"
-
- (If the numerical values are different for your setup, substitute the
- ones that correspond to your display. The above xmodmap scheme can
- often be used to work around other ambiguous keysym to keycode
- mappings.)
-
- Alternatively, here are some x11vnc options to try to work around the
- problem:
- -modtweak
-
- and
- -remap less-comma
-
- These are convenient in that they do not modify the actual X server
- settings. The former (-modtweak) is a mode that monitors the state of
- the Shift and AltGr modifiers and tries to deduce the correct keycode
- sequence to send. Since Jul/2004 -modtweak is now the default. The
- latter (-remap less-comma) is an immediate remapping of the keysym
- less to the keysym comma when it comes in from a client (so when Shift
- is down the comma press will yield "<".)
-
- See also the FAQ about the -xkb option as a possible workaround using
- the XKEYBOARD extension.
-
- Note that the -debug_keyboard option prints out much info for every
- keystroke to aid debugging keyboard problems.
-
-
- Q-89: Extra Character Inserted, E.g.: When I try to type a "<" (i.e.
- less than) instead I get "<," (i.e. an extra comma.)
-
- This is likely because you press "Shift" then "<" but then released
- the Shift key before releasing the "<". Because of a keymapping
- ambiguity the last event "< up" is interpreted as "," because that key
- unshifted is the comma.
-
- This extra character insertion will happen for other combinations of
- characters: in general it can happen whenever the Shift key is
- released early.
-
- This should not happen in -xkb mode, because it works hard to resolve
- the ambiguities. If you do not want to use -xkb, try the option
- -sloppy_keys to attempt a similar type of algorithm.
-
- One user had this problem for Italian and German keyboards with the
- key containing ":" and "." When he typed ":" he would get an extra "."
- inserted after the ":". The solution was -sloppy_keys.
-
-
- Q-90: I'm using an "international" keyboard (e.g. German "de", or
- Danish "dk") and the -modtweak mode works well if the VNC viewer is
- run on a Unix/Linux machine with a similar keyboard. But if I run
- the VNC viewer on Unix/Linux with a different keyboard (e.g. "us") or
- Windows with any keyboard, I can't type some keys like: "@", "$",
- "<", ">", etc. How can I fix this?
-
- The problem with Windows is it does not seem to handle AltGr well. It
- seems to fake it up by sending Control_L+Alt_R to applications. The
- Windows VNC viewer sends those two down keystrokes out on the wire to
- the VNC server, but when the user types the next key to get, e.g., "@"
- the Windows VNC viewer sends events bringing the up the
- Control_L+Alt_R keys, and then sends the "@" keysym by itself.
-
- The Unix/Linux VNC viewer on a "us" keyboard does a similar thing
- since "@" is the Shift of the "2" key. The keysyms Shift and "@" are
- sent to the VNC server.
-
- In both cases no AltGr is sent to the VNC server, but we know AltGr is
- needed on the physical international keyboard to type a "@".
-
- This all worked fine with x11vnc running with the -modtweak option (it
- figures out how to adjust the Modifier keys (Shift or AltGr) to get
- the "@".) However it fails under recent versions of XFree86 (and the
- X.org fork.) These run the XKEYBOARD extension by default and make
- heavy use of it to handle international keyboards.
-
- To make a long story short, on these newer XFree86 setups the
- traditional X keymap lookup x11vnc uses is no longer accurate. x11vnc
- can't find the keysym "@" anywhere in the keymapping! (even though it
- is in the XKEYBOARD extended keymapping.)
-
- How to Solve: As of Jul/2004 x11vnc has two changes:
- * -modtweak (tweak Modifier keys) is now the default (use
- -nomodtweak to go back to the old way)
- * there is a new option -xkb to use the XKEYBOARD extension API to
- do the Modifier key tweaking.
-
- The -xkb option seems to fix all of the missing keys: "@", "<", ">",
- etc.: it is recommended that you try it if you have this sort of
- problem. Let us know if there are any remaining problems (see the next
- paragraph for some known problems.) If you specify the -debug_keyboard
- (aka -dk) option twice you will get a huge amount of keystroke
- debugging output (send it along with any problems you report.)
-
- Update: as of Jun/2005 x11vnc will try to automatically enable -xkb if
- it appears that would be beneficial (e.g. if it sees any of "@", "<",
- ">", "[" and similar keys are mapped in a way that needs the -xkb to
- access them.) To disable this automatic check use -noxkb.
-
- Known problems:
- * One user had to disable a "ghost" Mode_switch key that was causing
- problems under -xkb. His physical AltGr key was bound to
- ISO_Level3_Shift (which seems to be the XKEYBOARD way of doing
- things), while there was a ghost key Mode_switch (which seems to
- be obsolete) in the mapping as well. Both of these keysyms were
- bound to Mod5 and x11vnc was unfortunately choosing Mode_switch.
- From the x11vnc -xkb -dk -dk output it was noted that Mode_switch
- was attached to keycode 93 (no physical key generates this
- keycode) while ISO_Level3_Shift was attached to keycode 113. The
- keycode skipping option was used to disable the ghost key:
- -skip_keycodes 93
- * In implementing -xkb we noticed that some characters were still
- not getting through, e.g. "~" and "^". This is not really an
- XKEYBOARD problem. What was happening was the VNC viewer was
- sending the keysyms asciitilde and asciicircum to x11vnc, but on
- the X server with the international keyboard those keysyms were
- not mapped to any keys. So x11vnc had to skip them (Note: as of
- May/2005 they are added by default see -add_keysyms below.)
- The way these characters are typically entered on international
- keyboards is by "dead" (aka "mute") keys. E.g. to enter "~" at the
- physical display the keysym dead_tilde is pressed and released
- (this usually involves holding AltGr down while another key is
- pressed) and then space is pressed. (this can also be used get
- characters with the "~" symbol on top, e.g. "ã" by typing "a"
- instead of space.)
- What to do? In general the VNC protocol has not really solved this
- problem: what should be done if the VNC viewer sends a keysym not
- recognized by the VNC server side? Workarounds can possibly be
- created using the -remap x11vnc option:
- -remap asciitilde-dead_tilde,asciicircum-dead_circumflex
- etc. Use -remap filename if the list is long. Please send us your
- workarounds for this problem on your keyboard. Perhaps we can have
- x11vnc adjust automatically at some point. Also see the
- -add_keysyms option in the next paragraph.
- Update: for convenience "-remap DEAD" does many of these mappings
- at once.
- * To complement the above workaround using the -remap, an option
- -add_keysyms was added. This option instructs x11vnc to bind any
- unknown Keysyms coming in from VNC viewers to unused Keycodes in
- the X server. This modifies the global state of the X server. When
- x11vnc exits it removes the extra keymappings it created. Note
- that the -remap mappings are applied first, right when the Keysym
- is received from a VNC viewer, and only after that would
- -add_keysyms, or anything else, come into play.
- Update: -add_keysyms is now on by default. Use -noadd_keysyms to
- disable.
-
-
- Q-91: When typing I sometimes get double, triple, or more of my
- keystrokes repeated. I'm sure I only typed them once, what can I do?
-
- This may be due to an interplay between your X server's key autorepeat
- delay and the extra time delays caused by x11vnc processing.
-
- Short answer: disable key autorepeating by running the command "xset r
- off" on the Xserver where x11vnc is run (restore via "xset r on") or
- use the new (Jul/2004) -norepeat x11vnc option. You will still have
- autorepeating because that is taken care of on your VNC viewer side.
-
- Update: as of Dec/2004 -norepeat is now the default. Use -repeat to
- disable it.
-
- Details:
- suppose you press a key DOWN and it generates changes in large regions
- of the screen. The CPU and I/O work x11vnc does for the large screen
- change could be longer than your X server's key autorepeat delay.
- x11vnc may not get to processing the key UP event until after the
- screen work is completed. The X server believes the key has been held
- down all this time, and applies its autorepeat rules.
-
- Even without inducing changes in large regions of the screen, this
- problem could arise when accessing x11vnc via a dialup modem or
- otherwise high latency link (e.g. > 250 ms latency.)
-
- Look at the output of "xset q" for the "auto repeat delay" setting. Is
- it low (e.g. < 300 ms)? If you turn off autorepeat completely: "xset r
- off", does the problem go away?
-
- The workaround is to manually apply "xset r off" and "xset r on" as
- needed, or to use the -norepeat (which has since Dec/2004 been made
- the default.) Note that with X server autorepeat turned off the VNC
- viewer side of the connection will (nearly always) do its own
- autorepeating so there is no big loss here, unless someone is also
- working at the physical display and misses his autorepeating.
-
-
- Q-92: The x11vnc -norepeat mode is in effect, but I still get repeated
- keystrokes!!
-
- Are you using x11vnc to log in to an X session via display manager?
- (as described in this FAQ) If so, x11vnc is starting before your
- session and it disables autorepeat when you connect, but then after
- you log in your session startup (GNOME, KDE, ...) could be resetting
- the autorepeat to be on. Or it could be something inside your desktop
- trying to be helpful that decides to turn it back on.
-
- x11vnc in -norepeat mode will by default reset autorepeat to off 2
- times (to help get thru the session startup problem), but it will not
- continue to battle with things turning autorepeat back on. It will
- also turn autorepeat off whenever it goes from a state of zero clients
- to one client. You can adjust the number of resets via "-norepeat N",
- or use "-norepeat -1" to have it keep resetting it whenever autorepeat
- gets turned back on when clients are connected.
-
- In general you can manually turn autorepeating off by typing "xset r
- off", or a using desktop utility/menu, or "x11vnc -R norepeat". If
- something in your desktop is automatically turning it back on you
- should figure out how to disable that somehow.
-
-
- Q-93: After using x11vnc for a while, I find that I cannot type some
- (or any) characters or my mouse clicks and drags no longer have any
- effect, or they lead to strange effects. What happened?
-
- Probably a modifier key, e.g. Control or Alt is "stuck" in a pressed
- down state.
-
- This happens for VNC in general by the following mechanism. Suppose on
- the Viewer side desktop there is some hot-key to switch
- desktops/rooms/spaces, etc. E.g. suppose Alt+LeftArrow moves to the
- left desktop/room/space. Or suppose an Alt+hotkey combination
- iconifies a window. This can leave the Alt key pressed down on the
- remote side.
-
- Consider the sequence that happens. The Alt_L key and then the
- LeftArrow key go down. Since you are inside the viewer the Alt_L key
- press is sent to the other side (x11vnc) and so it is pressed down in
- the remote desktop as well. (by "Alt_L" we mean the Alt key on the
- left-hand side of the keyboard.) Your local desktop (where the VNC
- Viewer is running) then warps to the new desktop/room/space: Leaving
- the Alt_L key still pressed down in the remote desktop.
-
- If someone is sitting at the desktop, or when you return in the viewer
- it may be very confusing because the Alt_L is still pressed down but
- you (or the person sitting at the desktop) do not realize this.
- Depending on which remote desktop (x11vnc side) is used, it can act
- very strangely.
-
- A quick workaround when you notice this is to press and release all of
- the Alt, Shift, Control, Windows-Flag, modifier keys to free the
- pressed one. You need to do this for both the left and right Shift,
- Alt, Control, etc. keys to be sure.
-
- Note that many VNC Viewers try to guard against this when they are
- notified by the window system that the viewer app has "lost focus".
- When it receives the "lost focus" event, the viewer sends VNC
- Key-Release events for all modifier keys that are currently pressed
- down. This does not always work, however, since it depends on how the
- desktop manages these "warps". If the viewer is not notified it cannot
- know it needs to release the modifiers.
-
- You can also use the -clear_mods option to try to clear all of the
- modifier keys at x11vnc startup. You will still have to be careful
- that you do not leave the modifier key pressed down during your
- session. It is difficult to prevent this problem from occurring (short
- of using -remap to prevent sending all of the problem modifier keys,
- which would make the destkop pretty unusable.)
-
- During a session these x11vnc remote control commands can also help:
- x11vnc -R clear_mods
- x11vnc -R clear_keys
- x11vnc -R clear_locks
- x11vnc -R clear_all
-
- A similar problem can occur if you accidentally press the Caps_Lock or
- Num_Lock down. When these are locked on the remote side it can
- sometimes lead to strange desktop behavior (e.g. cannot drag or click
- on windows.) As above you may not notice this because the lock isn't
- down on the local (Viewer) side. See this FAQ on lock keys problem.
- These options may help avoid the problem: -skip_lockkeys and
- -capslock. See also -clear_all.
-
-
- Q-94: The machine where I run x11vnc has an AltGr key, but the local
- machine where I run the VNC viewer does not. Is there a way I can map
- a local unused key to send an AltGr? How about a Compose key as well?
-
- Something like "-remap Super_R-Mode_switch" x11vnc option may work.
- Note that Super_R is the "Right Windoze(tm) Flaggie" key; you may want
- to choose another. The -debug_keyboard option comes in handy in
- finding keysym names (so does xev(1).)
-
- For Compose how about "-remap Menu-Multi_key" (note that Multi_key is
- the official name for Compose.) To do both at the same time: "-remap
- Super_R-Mode_switch,Menu-Multi_key" or use "-remap filename" to
- specify remappings from a file.
-
-
- Q-95: I have a Sun machine I run x11vnc on. Its Sun keyboard has just
- one Alt key labelled "Alt" and two Meta keys labelled with little
- diamonds. The machine where I run the VNC viewer only has Alt keys.
- How can I send a Meta keypress? (e.g. emacs needs this)
-
- Here are a couple ideas. The first one is to simply use xmodmap(1) to
- adjust the Sun X server. Perhaps xmodmap -e "keysym Alt_L = Meta_L
- Alt_L" will do the trick. (there are other ways to do it, one user
- used: xmodmap -e "keycode 26 = Meta_L" for his setup.)
-
- Since xmodmap(1) modifies the X server mappings you may not want to do
- this (because it affects local work on that machine.) Something like
- the -remap Alt_L-Meta_L to x11vnc may be sufficient for ones needs,
- and does not modify the X server environment. Note that you cannot
- send Alt_L in this case, maybe -remap Super_L-Meta_L would be a better
- choice if the Super_L key is typically unused in Unix.
-
-
- Q-96: Running x11vnc on HP-UX I cannot type "#" I just get a "3"
- instead.
-
- One user reports this problem on HP-UX Rel_B.11.23. The problem was
- traced to a strange keyboard mapping for the machine (e.g. xmodmap -pk
- output) that looked like:
- ...
- 039 2 at at at
- ...
- 047 3 numbersign numbersign numbersign
-
- and similar triple mappings (with two in the AltGr/Mode_switch group)
- of a keysum to a single keycode.
-
- Use the -nomodtweak option as a workaround. You can also use xmodmap
- to correct these mappings in the server, e.g.:
- xmodmap -e "keycode 47 = 3 numbersign"
-
- Also, as of Feb/2007, set the environment variable MODTWEAK_LOWEST=1
- (either in your shell or via "-env MODTWEAK_LOWEST=1" option) to
- handle these mappings better.
-
-
- Q-97: Can I map a keystroke to a mouse button click on the remote
- machine?
-
- This can be done directly in some X servers using AccessX and
- Pointer_EnableKeys, but is a bit awkward. It may be more convenient to
- have x11vnc do the remapping. This can be done via the -remap option
- using the fake "keysyms" Button1, Button2, etc. as the "to" keys (i.e.
- the ones after the "-")
-
- As an example, consider a laptop where the VNC viewer is run that has
- a touchpad with only two buttons. It is difficult to do a middle
- button "paste" because (using XFree86/Xorg Emulate3Buttons) you have
- to click both buttons on the touch pad at the same time. This
- remapping:
- -remap Super_R-Button2
-
- maps the Super_R "flag" key press to the Button2 click, thereby making
- X pasting a bit easier.
-
- Note that once the key goes down, the button down and button up events
- are generated immediately on the x11vnc side. When the key is released
- (i.e. goes up) no events are generated.
-
- Q-98: How can I get Caps_Lock to work between my VNC viewer and
- x11vnc?
-
- This is a little tricky because it is possible to get the Caps_Lock
- state out of sync between your viewer-side machine and the x11vnc-side
- X server. For best results, we recommend not ever letting the
- Caps_Lock keypresses be processed by x11vnc. That way when you press
- Caps_Lock in the viewer your local machine goes into the Caps_Lock on
- state and sends keysym "A" say when you press "a". x11vnc will then
- fake things up so that Shift is held down to generate "A". The
- -skip_lockkeys option should help to accomplish this. For finer grain
- control use something like: "-remap Caps_Lock-None".
-
- Also try the -nomodtweak and -capslock options.
-
- Another useful option that turns off any Lock keys on the remote side
- at startup and end is the -clear_all option. During a session you can
- run these remote control commands to modify the Lock keys:
- x11vnc -R clear_locks
- x11vnc -R clear_all
-
- the former will try to unset any Lock keys, the latter will do same
- and also try to make it so no key is pressed down (e.g. "stuck" Alt_L,
- etc.)
- [Screen Related Issues and Features]
-
- Q-99: The remote display is larger (in number of pixels) than the
- local display I am running the vncviewer on. I don't like the
- vncviewer scrollbars, what I can do?
-
- vncviewer has a option (usually accessible via F8 key or -fullscreen
- option) for vncviewer to run in full screen, where it will
- automatically scroll when the mouse is near the edge of the current
- view. For quick scrolling, also make sure Backing Store is enabled on
- the machine vncviewer is run on. (XFree86/Xorg disables it by default
- for some reason, add Option "backingstore" to XF86Config on the
- vncviewer side.)
-
- BTW, contact me if you are having problems with vncviewer in
- fullscreen mode with your window manager (i.e. no keyboard response.)
- I have a workaround for vncviewer using XGrabServer().
-
- There may also be scaling viewers out there (e.g. TightVNC or UltraVNC
- on Windows) that automatically shrink or expand the remote framebuffer
- to fit the local display. Especially for hand-held devices. See also
- the next FAQ on x11vnc scaling.
-
-
- Q-100: Does x11vnc support server-side framebuffer scaling? (E.g. to
- make the desktop smaller.)
-
- As of Jun/2004 x11vnc provides basic server-side scaling. It is a
- global scaling of the desktop, not a per-client setting. To enable it
- use the "-scale fraction" option. "fraction" can either be a floating
- point number (e.g. -scale 0.75) or the alternative m/n fraction
- notation (e.g. -scale 3/4.) Note that if fraction is greater than one
- the display is magnified.
-
- Extra resources (CPU, memory I/O, and memory) are required to do the
- scaling. If the machine is slow where x11vnc is run with scaling
- enabled, the interactive response can be unacceptable. OTOH, if run
- with scaling on a fast machine the performance degradation is usually
- not a big issue or even noticeable.
-
- It may help to compile x11vnc with compiler option -O3 or -O4 to speed
- up the scaling code. Set the CFLAGS env. var. before running
- configure.
-
- Also, if you just want a quick, rough "thumbnail" of the display you
- can append ":nb" to the fraction to turn on "no blending" mode. E.g.:
- "-scale 1/3:nb" Fonts will be difficult to read, but the larger
- features will be recognizable. BTW, "no blending" mode is forced on
- when scaling 8bpp PseudoColor displays (because blending an indexed
- colormap is a bad idea and leads to random colors, use :fb to force it
- on.)
-
- One can also use the ":nb" with an integer scale factor (say "-scale
- 2:nb") to use x11vnc as a screen magnifier for vision impaired
- applications. Since with integer scale factors the framebuffers become
- huge and scaling operations time consuming, be sure to use ":nb" for
- the fastest response.
-
- In general for a scaled display if you are using a TightVNC viewer you
- may want to turn off jpeg encoding (e.g. vncviewer -nojpeg host:0.)
- There appears to be a noise enhancement effect, especially for regions
- containing font/text: the scaling can introduce some pixel artifacts
- that evidently causes the tight encoding algorithm to incorrectly
- detect the regions as image data and thereby introduce additional
- pixel artifacts due to the lossiness of the jpeg compression
- algorithm. Experiment to see if -nojpeg vncviewer option improves the
- readability of text when using -scale to shrink the display size. Also
- note that scaling may actually slow down the transfer of text regions
- because after being scaled they do not compress as well. (this can
- often be a significant slowdown, e.g. 10X.)
-
- Another issue is that it appears VNC viewers require the screen width
- to be a multiple of 4. When scaling x11vnc will round the width to the
- nearest multiple of 4. To disable this use the ":n4" sub option (like
- ":nb" in the previous paragraph; to specify both use a comma:
- ":nb,n4", etc.)
-
- If one desires per-client scaling for something like 1:1 from a
- workstation and 1:2 from a smaller device (e.g. handheld), currently
- the only option is to run two (or more) x11vnc processes with
- different scalings listening on separate ports (-rfbport option, etc.)
-
- Update: As of May/2006 x11vnc also supports the UltraVNC server-side
- scaling. This is a per-client scaling by factors 1/2, 1/3, ... and so
- may be useful for PDA's ("-scale 1/2", etc. will give similar results
- except that it applies to all clients.) You may need to supply
- "-rfbversion 3.6" for this to be recognized by UltraVNC viewers.
-
- BTW, whenever you run two or more x11vnc's on the same X display and
- use the GUI, then to avoid all of the x11vnc's simultaneously
- answering the gui you will need to use something like "-connect file1
- -gui ..." with different connect files for each x11vnc you want to
- control via the gui (or remote-control.) The "-connect file1" usage
- gives separate communication channels between a x11vnc process and the
- gui process. Otherwise they all share the same X property channels:
- VNC_CONNECT and X11VNC_REMOTE.
-
- Update: As of Mar/2005 x11vnc now scales the mouse cursor with the
- same scale factor as the screen. If you don't want that, use the
- "-scale_cursor frac" option to set the cursor scaling to a different
- factor (e.g. use "-scale_cursor 1" to keep the cursor at its natural
- unscaled size.)
-
-
- Q-101: Does x11vnc work with Xinerama? (i.e. multiple monitors joined
- together to form one big, single screen.)
-
- Yes, it should generally work because it simply polls the big
- effective screen.
-
- If the viewing-end monitor is not as big as the remote Xinerama
- display, then the vncviewer scrollbars, etc, will have to be used to
- pan across the large area. However one user started two x11vnc's, one
- with "-clip 1280x1024+0+0" and the other with "-clip 1280x1024+1280+0"
- to split the big screen into two and used two VNC viewers to access
- them.
-
- As of Jun/2008: Use "-clip xinerama0" to clip to the first xinerama
- sub-screen (if xinerama is active.) xinerama1 for the 2nd sub-screen,
- etc. This way you don't need to figure out the WxH+X+Y of the desired
- xinerama sub-screen. screens are sorted in increasing distance from
- the (0,0) origin (I.e. not the Xserver's order.)
-
- There are a couple potential issues with Xinerama however. If the
- screen is not rectangular (e.g. 1280x1024 and 1024x768 monitors joined
- together), then there will be "non-existent" areas on the screen. The
- X server will return "garbage" image data for these areas and so they
- may be distracting to the viewer. The -blackout x11vnc option allows
- you to blacken-out rectangles by manually specifying their WxH+X+Y
- geometries. If your system has the libXinerama library, the -xinerama
- x11vnc option can be used to have it automatically determine the
- rectangles to be blackened out. (Note on 8bpp PseudoColor displays the
- fill color may not be black.) Update: -xinerama is now on by default.
-
- Some users have reported that the mouse does not behave properly for
- their Xinerama display: i.e. the mouse cannot be moved to all regions
- of the large display. If this happens try using the -xwarppointer
- option. This instructs x11vnc to fake mouse pointer motions using the
- XWarpPointer function instead of the XTestFakeMotionEvent XTEST
- function. (This may be due to a bug in the X server for XTEST when
- Xinerama is enabled.) Update: As of Dec/2006 -xwarppointer will be
- applied automatically if Xinerama is detected. To disable use:
- -noxwarppointer
-
-
- Q-102: Can I use x11vnc on a multi-headed display that is not Xinerama
- (i.e. separate screens :0.0, :0.1, ... for each monitor)?
-
- You can, but it is a little bit awkward: you must start separate
- x11vnc processes for each screen, and on the viewing end start up
- separate VNC viewer processes connecting to them. e.g. on the remote
- end:
- x11vnc -display :0.0 -bg -q -rfbport 5900
- x11vnc -display :0.1 -bg -q -rfbport 5901
-
- (this could be automated in the display manager Xsetup for example)
- and then on the local machine where you are sitting:
- vncviewer somehost:0 &
- vncviewer somehost:1 &
-
- Note: if you are running on Solaris 8 or earlier you can easily hit up
- against the maximum of 6 shm segments per process (for Xsun in this
- case) from running multiple x11vnc processes. You should modify
- /etc/system as mentioned in another FAQ to increase the limit. It is
- probably also a good idea to run with the -onetile option in this case
- (to limit each x11vnc to 3 shm segments), or even -noshm to use no shm
- segments.
-
-
- Q-103: Can x11vnc show only a portion of the display? (E.g. for a
- special purpose application or a very large screen.)
-
- As of Mar/2005 x11vnc has the "-clip WxH+X+Y" option to select a
- rectangle of width W, height H and offset (X, Y). Thus the VNC screen
- will be the clipped sub-region of the display and be only WxH in size.
- One user used -clip to split up a large Xinerama screen into two more
- managable smaller screens.
-
- This also works to view a sub-region of a single application window if
- the -id or -sid options are used. The offset is measured from the
- upper left corner of the selected window.
-
-
- Q-104: Does x11vnc support the XRANDR (X Resize, Rotate and
- Reflection) extension? Whenever I rotate or resize the screen x11vnc
- just seems to crash.
-
- As of Dec/2004 x11vnc supports XRANDR. You enable it with the -xrandr
- option to make x11vnc monitor XRANDR events and also trap X server
- errors if the screen change occurred in the middle of an X call like
- XGetImage. Once it traps the screen change it will create a new
- framebuffer using the new screen.
-
- If the connected vnc viewers support the NewFBSize VNC extension
- (Windows TightVNC viewer and RealVNC 4.0 windows and Unix viewers do)
- then the viewer will automatically resize. Otherwise, the new
- framebuffer is fit as best as possible into the original viewer size
- (portions of the screen may be clipped, unused, etc.) For these
- viewers you can try the -padgeom option to make the region big enough
- to hold all resizes and rotations. We have fixed this problem for the
- TightVNC Viewer on Unix: SSVNC
-
- If you specify "-xrandr newfbsize" then vnc viewers that do not
- support NewFBSize will be disconnected before the resize. If you
- specify "-xrandr exit" then all will be disconnected and x11vnc will
- terminate.
-
-
- Q-105: Independent of any XRANDR, can I have x11vnc rotate and/or
- reflect the screen that the VNC viewers see? (e.g. for a handheld
- whose screen is rotated 90 degrees.)
-
- As of Jul/2006 there is the -rotate option allow this. E.g's: "-rotate
- +90", "-rotate -90", "-rotate x", etc.
-
-
- Q-106: Why is the view in my VNC viewer completely black? Or why is
- everything flashing around randomly?
-
- See the next FAQ for a possible explanation.
-
-
- Q-107: I use Linux Virtual Terminals (VT's) to implement 'Fast User
- Switching' between users' sessions (e.g. Betty is on Ctrl-Alt-F7,
- Bobby is on Ctrl-Alt-F8, and Sid is on Ctrl-Alt-F1: they use those
- keystrokes to switch between their sessions.) How come the view in a
- VNC viewer connecting to x11vnc is either completely black or
- otherwise all messed up unless the X session x11vnc is attached to is
- in the active VT?
-
- This seems to have to do with how applications (the X server processes
- in this case) must "play nicely" if they are not on the active VT
- (sometimes called VC for virtual console.) That is, they should not
- read from the keyboard or mouse or manage the video display unless
- they have the active VT. Given that it appears the XGetImage() call
- must ultimately retrieve the framebuffer data from the video hardware
- itself, it would make sense x11vnc's polling wouldn't work unless the
- X session had active control of the VT.
-
- There does not seem to be an easy way to work around this. Even xwd(1)
- doesn't work in this case (try it.) Something would need to be done at
- a lower level, say in the XFree86/Xorg X server. Also, using the
- Shadow Framebuffer (a copy of the video framebuffer is kept in main
- memory) does not appear to fix the problem.
-
- If no one is sitting at the workstation and you just want to remotely
- switch the VT over to the one associated with your X session (so
- x11vnc can poll it correctly), one can use the chvt(1) command, e.g.
- "chvt 7" for VT #7.
-
-
- Q-108: I am using x11vnc where my local machine has "popup/hidden
- taskbars" and the remote display where x11vnc runs also has
- "popup/hidden taskbars" and they interfere and fight with each other.
- What can I do?
-
- When you move the mouse to the edge of the screen where the popups
- happen, the taskbars interfere with each other in strange ways. This
- sometimes happens where the local machine is GNOME or Mac OS X and the
- remote machine is GNOME. Is there a way to temporarily disable one or
- both of these magic desktop taskbars?
-
- One x11vnc user suggests: it should be straightforward to right mouse
- click on the task bar panel, and uncheck "enable auto-hide" from the
- panel properties dialog box. This will make the panel always visible.
-
- Q-109: Help! x11vnc and my KDE screensaver keep switching each other
- on and off every few seconds.
-
- This is a new (Jul/2006) problem seen, say, on the version of KDE that
- is shipped with SuSE 10.1. It is not yet clear what is causing this...
- If you move the mouse through x11vnc the screensaver shuts off like it
- should but then a second or two after you stop moving the mouse the
- screensaver snaps back on.
-
- This may be a bug in kdesktop_lock. For now the only workaround is to
- disable the screensaver. You can try using another one such as
- straight xscreensaver (see the instructions here for how to disable
- kdesktop_lock.) If you have more info on this or see it outside of KDE
- please let us know.
-
- Update: It appears this is due to kdesktop_lock enabling the screen
- saver when the Monitor is in DPMS low-power state (e.g. standby,
- suspend, or off.) In Nov/2006 the x11vnc -nodpms option was added as a
- workaround. Normally it is a good thing that the monitor powers down
- (since x11vnc can still poll the framebuffer in this state), but if
- you experience the kdesktop_lock problem you can specify the "-nodpms"
- option to keep the Monitor out of low power state while VNC clients
- are connected. This is basically the same as typing "xset dpms force
- on" periodically. (if you don't want to do these things just disable
- the screensaver.) Feel free to file a bug against kdesktop_lock with
- KDE.
-
- Q-110: I am running the compiz 3D window manager (or beryl, MythTv,
- Google Earth, or some other OpenGL app) and I do not get screen
- updates in x11vnc.
-
- This appears to be because the 3D OpenGL/GLX hardware screen updates
- do not get reported via the XDAMAGE mechanism. So this is a bug in
- compiz/beryl or XDAMAGE/Xorg or the (possibly 3rd party) video card
- driver.
-
- As a workaround apply the -noxdamage option. As of Feb/2007 x11vnc
- will try to autodetect the problem and disable XDAMAGE if is appears
- to be missing a lot of updates. But if you know you are using compiz
- you might as well always supply -noxdamage. Thanks to this user who
- reported the problem and discovered the workaround.
-
- A developer for MiniMyth reports that the 'alphapulse' tag of the
- theme G.A.N.T. can also cause problems, and should be avoided when
- using VNC.
-
- Please report a bug or complaint to Beryl/Compiz and/or Xorg about
- this: running x11vnc with -noxdamage disables a nice improvement in
- responsiveness (especially for typing) and also leads to unnecessary
- CPU and memory I/O load due to the extra polling.
-
- Update: as of May/2010 NVIDIA may have fixed this problem in their
- proprietary drivers. See the NVIDIA Release Notes. (look for
- 'x11vnc'.)
-
- Q-111: Can I use x11vnc to view my VMWare session remotely?
-
- Yes, since VMWare usually runs as an X application you can view it via
- x11vnc in the normal way.
-
- Note that VMWare has several viewing modes:
- * Normal X application window (with window manager frame)
- * Quick-Switch mode (with no window manager frame)
- * Fullscreen mode
-
- The way VMWare does Fullscreen mode on Linux is to display the Guest
- desktop in a separate Virtual Terminal (e.g. VT 8) (see this FAQ on
- VT's for background.) Unfortunately, this Fullscreen VT is not an X
- server. So x11vnc cannot access it (however, see this discussion of
- -rawfb for a possible workaround.) x11vnc works fine with "Normal X
- application window" and "Quick-Switch mode" because these use X.
-
- Update: It appears the in VMWare 5.x the Fullscreen mode is X, so
- x11vnc access does work.
-
- One user reports he left his machine with VMWare in the Fullscreen
- mode, and even though his X session wasn't in the active VT, he could
- still connect x11vnc to the X session and pass the keystrokes Ctrl-Alt
- (typing "blind") to the VMWare X app. This induced VMWare to switch
- out of Fullscreen into Normal X mode and he could continue working in
- the Guest desktop remotely.
-
-
- Aside: Sometimes it is convenient (for performance, etc.) to start
- VMWare in its own X session using startx(1). This can be used to have
- a minimal window manger (e.g. twm or even no window manager), to
- improve response. One can also cut the display depth (e.g. to 16bpp)
- in this 2nd X session to improve video performance. This 2nd X session
- emulates Fullscreen mode to some degree and can be viewed via x11vnc
- as long as the VMWare X session is in the active VT.
-
- Also note that with a little bit of playing with "xwininfo -all
- -children" output one can extract the (non-toplevel) window-id of the
- of the Guest desktop only when VMWare is running as a normal X
- application. Then one can export just the guest desktop (i.e. without
- the VMWare menu buttons) by use of the -id windowid option. The
- caveats are the X session VMWare is in must be in the active VT and
- the window must be fully visible, so this mode is not terribly
- convenient, but could be useful in some circumstances (e.g. running
- VMWare on a very powerful server machine in a server room that happens
- to have a video card, (but need not have a monitor, Keyboard or
- mouse).)
-
-
-
- [Exporting non-X11 devices via VNC]
-
- Q-112: Can non-X devices (e.g. a raw framebuffer) be viewed (and even
- controlled) via VNC with x11vnc?
-
- As of Apr/2005 there is support for this. Two options were added:
- "-rawfb string" (to indicate the raw frame buffer device, file, etc.
- and its parameters) and "-pipeinput command" (to provide an external
- program that will inject or otherwise process mouse and keystroke
- input.) Some useful -pipeinput schemes, VID, CONSOLE, and UINPUT, have
- since been built into x11vnc for convenience.
-
- This non-X mode for x11vnc is somewhat experimental because it is so
- removed in scope from the intended usage of the tool. Incomplete
- attempt is made to make all of the other options consistent with non-X
- framebuffer polling. So all of the X-related options (e.g.
- -add_keysyms, -xkb) are just ignored or may cause an error if used. Be
- careful applying such an option via remote control.
-
- The format for the -rawfb string is:
- -rawfb <type>:<object>@<W>x<H>x<bpp>[-<BPL>][:<R>/<G>/<B>][+<offset>]
-
- There are also some useful aliases (e.g. "console".) Some examples:
- -rawfb shm:210337933@800x600x32:ff/ff00/ff0000
-
- -rawfb map:/dev/fb0@1024x768x16
-
- -rawfb map:/tmp/Xvfb_screen0@640x480x8+3232
-
- -rawfb file:/tmp/my.pnm@250x200x24+37
-
- -rawfb file:/dev/urandom@128x128x8
-
- -rawfb snap:/dev/video0@320x240x24 -24to32
-
- -rawfb console
-
- -rawfb vt2
-
- -rawfb video
-
- -rawfb setup:mycmd.sh
-
- So the type can be "shm" for shared memory objects, and "map" or
- "file" for file objects. "map" uses mmap(2) to map the file into
- memory and is preferred over "file" (that uses the slower lseek(2)
- access method.) Only use file if map isn't working. BTW, "mmap" is an
- alias for "map" and if you do not supply a type and the file exists,
- map is assumed (see the -help output and below for some exceptions to
- this.) The "snap:" setting applies the -snapfb option with "file:"
- type reading (this is useful for exporting webcams or TV tuner video;
- see the next FAQ for more info.)
-
- Also, if the string is of the form "setup:cmd" then cmd is run and the
- first line of its output retrieved and used as the rawfb string. This
- allows initializing the device, determining WxHxB, etc.
-
- The object will be the numerical shared memory id for the case of shm.
- The idea here is some other program has created this shared memory
- segment and periodically updates it with new framebuffer data. x11vnc
- polls the area for changes. See shmat(2) and ipcs(8) for more info.
- The ipcs command will list current shared memory segments on the
- system. Sometimes you can snoop on a program's framebuffer it did not
- expect you would be polling!
-
- The object will be the path to the regular or character special file
- for the cases of map and file. The idea here is that in the case of a
- regular file some other program is writing/updating framebuffer image
- data to it. In the case of a character special (e.g. /dev/fb0) it is
- the kernel that is "updating" the framebuffer data.
-
- In most cases x11vnc needs to be told the width, height, and number of
- bits per pixel (bpp) of the framebuffer. This is the @WxHxB field. For
- the case of the Linux framebuffer device, /dev/fb0, the fbset(8) may
- be of use (but may not always be accurate for what is currently
- viewable.) In general some guessing may be required, especially for
- the bpp. Update: in "-rawfb console" mode x11vnc will use the linuxfb
- API to try to guess (it is still not always accurate.) Also try
- "-rawfb vtN" (on x11vnc 0.9.7 and later) for the N-th Linux text
- console (aka virtual terminal.) If the number of Bytes Per Line is not
- WxHxB/8 (i.e. the framebuffer lines are padded) you can specify this
- information after WxHxB via "-BPL", e.g. @800x600x16-2048
-
- Based on the bpp x11vnc will try to guess the red, green, and blue
- masks (these indicate which bits correspond to each color.) It if gets
- it wrong you can specify them manually via the optional ":R/G/B"
- field. E.g. ":0xff0000/0x00ff00/0x0000ff" (this is the default for
- 32bpp.)
-
- Finally, the framebuffer may not begin at the beginning of the memory
- object, so use the optional "+offset" parameter to indicate where the
- framebuffer information starts. So as an example, the Xvfb virtual
- framebuffer has options -shmem and -fbdir for exporting its virtual
- screen to either shm or a mapped file. The format of these is XWD and
- so the initial header should be skipped. BTW, since XWD is not
- strictly RGB the view will only be approximate, but usable. Of course
- for the case of Xvfb x11vnc can poll it much better via the X API, but
- you get the idea.
-
- By default in -rawfb mode x11vnc will actually close any X display it
- happened to open. This is basically to shake out bugs (e.g it will
- crash rather than mysteriously interacting with the X display.) If you
- want x11vnc to keep the X display open while polling the raw
- framebuffer prefix a "+" sign at the beginning of the string (e.g.
- +file:/dev/urandom@64x64x8) This could be convenient for keeping the
- remote control channel active (it uses X properties.) The "-connect
- /path/to/file" mechanism could also be used for remote control to
- avoid the X property channel. Rare usage, but if you also supply
- -noviewonly in this "+" mode then the mouse and keyboard input are
- still sent to the X display, presumably for doing something amusing
- with /dev/fb...
-
- Interesting Devices:. Here are some aliases for interesting device
- files that can be polled via -rawfb:
- -rawfb console /dev/fb0 Linux Console
- -rawfb vt2 /dev/vcsa2 Linux Console (e.g. virtual ter
-minal #2)
- -rawfb video /dev/video0 Video4Linux Capture device
- -rawfb rand /dev/urandom Random Bytes
- -rawfb null /dev/zero Zero Bytes (black screen)
-
- The Linux console, /dev/fb0, etc needs to have its driver enabled in
- the kernel. Some of the drivers are video card specific and
- accelerated. The console is either the Text consoles (usually
- tty1-tty6), or X graphical display (usually starting at tty7.) In
- addition to the text console other graphical ones may be viewed and
- interacted with as well, e.g. DirectFB or SVGAlib apps, VMWare non-X
- fullscreen, or Qt-embedded apps (PDAs/Handhelds.) By default the
- pipeinput mechanisms UINPUT and CONSOLE (keystrokes only) are
- automatically attempted in this mode under "-rawfb console".
-
- The Video4Linux Capture device, /dev/video0, etc is either a Webcam or
- a TV capture device and needs to have its driver enabled in the
- kernel. See this FAQ for details. If specified via "-rawfb Video" then
- the pipeinput method "VID" is applied (it lets you change video
- parameters dynamically via keystrokes.)
-
- The last two, /dev/urandom and /dev/zero are just for fun, but are
- also useful in testing.
-
-
- All of the above -rawfb options are just for viewing the raw
- framebuffer (although some of the aliases do imply keystroke and mouse
- pipeinput methods.) That may be enough for certain applications of
- this feature (e.g. suppose a video camera mapped its framebuffer into
- memory and you just wanted to look at it via VNC.)
- To handle the pointer and keyboard input from the viewer users the
- "-pipeinput cmd" option was added to indicate a helper program to
- process the user input. The input is streamed to it and looks
- something like this:
- Pointer 1 205 257 0 None
- Pointer 1 198 253 0 None
- Pointer 1 198 253 1 ButtonPress-1
- Pointer 1 198 253 0 ButtonRelease-1
- Pointer 1 198 252 0 None
- Keysym 1 1 119 w KeyPress
- Keysym 1 0 119 w KeyRelease
- Keysym 1 1 65288 BackSpace KeyPress
- Keysym 1 0 65288 BackSpace KeyRelease
- Keysym 1 1 112 p KeyPress
- Keysym 1 0 112 p KeyRelease
-
- Run "-pipeinput tee:/bin/cat" to get a description of the format. Note
- that the -pipeinput option is independent of -rawfb mode and so may
- have some other interesting uses. The "tee:" prefix means x11vnc will
- both process the user input and pipe it to the command. The default is
- to just pipe it to the -pipeinput command.
-
- Note the -pipeinput helper program could actually control the raw
- framebuffer. In the libvncserver CVS a simple example program
- x11vnc/misc/slide.pl is provided that demonstrates a simple jpeg
- "slideshow" application. Also the builtin "-pipeinput VID" mode does
- this for webcams and TV capture devices (/dev/video0.)
-
- The -pipeinput program is run with these environment variables set:
- X11VNC_PID, X11VNC_PROG, X11VNC_CMDLINE, X11VNC_RAWFB_STR to aid its
- knowing what is up.
-
- Another example provided in libvncserver CVS is a script to inject
- keystrokes into the Linux console (e.g. the virtual consoles:
- /dev/tty1, /dev/tty2, etc) in x11vnc/misc/vcinject.pl. It is based on
- the vncterm/LinuxVNC.c program also in the libvncserver CVS. So to
- view and interact with VT #2 (assuming it is the active VT) one can
- run something like:
- x11vnc -rawfb map:/dev/fb0@1024x768x16 -pipeinput './vcinject.pl 2'
-
- This assumes your Linux framebuffer device (/dev/fb0) is properly
- configured. See fbset(8) and other documentation. Try
- "file:/dev/fb0@WxHxB" as a last resort. Starting with x11vnc 0.8.1,
- the above VT injection is built in, as well as WxHxB determination.
- Just use something like:
- x11vnc -rawfb console
-
- this will try to guess the active virtual console (via /dev/tty0) and
- also the /dev/fb0 WxHxB and rgb masks automatically. Use, e.g.,
- "-rawfb console3" to force the VT number. This input method can be
- used generally via "-pipeinput CONSOLE". Also starting with x11vnc
- 0.8.2 the "-pipeinput UINPUT" mode is tried first (it does both
- keyboard and mouse input) and then falls back to CONSOLE mode if it is
- not available. Here is the -help output for this mode:
-
- If the rawfb string begins with "console" the framebuffer device
- /dev/fb0 is opened (this requires the appropriate kernel modules to
- be installed) and so is /dev/tty0. The latter is used to inject
- keystrokes (not all are supported, but the basic ones are.) You
- will need to be root to inject keystrokes. /dev/tty0 refers to the
- active VT, to indicate one explicitly, use "console2", etc. using
- the VT number.
-
- If the Linux version seems to be 2.6 or later and the "uinput"
- module appears to be present, then the uinput method will be used
- instead of /dev/ttyN. uinput allows insertion of BOTH keystrokes
- and mouse input and so it preferred when accessing graphical (e.g.
- Qt-embedded) linux console apps. See -pipeinput UINPUT below for
- more information on this mode (you may want to also use the
- -nodragging and -cursor none options.) Use "console0", etc or
- -pipeinput CONSOLE to force the /dev/ttyN method.
-
- Note you can change VT remotely using the chvt(1) command.
- Sometimes switching out and back corrects the framebuffer state.
-
- To skip input injecting entirely use "consolex".
-
- The string "/dev/fb0" (1, etc) can be used instead of "console".
- This can be used to specify a different framebuffer device, e.g.
- /dev/fb1. As a shortcut the "/dev/" can be dropped. If the name is
- something nonstandard, use "console:/dev/foofb"
-
- If you do not want x11vnc to guess the framebuffer's WxHxB and
- masks automatically (sometimes the kernel gives inaccurate
- information), specify them with a @WxHxB at the end of the string.
-
- The above is just an example of what can be done. Note that if you
- really want to view and interact with the Linux Text console it is
- better to use the more accurate and faster LinuxVNC program. The
- advantage x11vnc -rawfb might have is that it can allow interaction
- with a non-text application, e.g. one based on SVGAlib or Qt-embedded
- Also, for example the VMWare Fullscreen mode is actually viewable
- under -rawfb and can be interacted with if uinput is enabled.
-
- If the Linux uinput driver is available then full keystroke and mouse
- input into the Linux console can be performed. You may be able to
- enable uinput via commands like these:
- modprobe uinput
- mknod /dev/input/uinput c 10 223
-
- The -rawfb and -pipeinput features are intended to help one creatively
- "get out of a jam" (say on a legacy or embedded device) where X is
- absent or doesn't work properly. Feedback and bug reports are welcome.
- For more control and less overhead use libvncserver in your own C
- program that passes the framebuffer to libvncserver.
-
-
- Q-113: Can I export the Linux Console (Virtual Terminals) via VNC
- using x11vnc?
-
- Yes, you may need to be root to access the devices that make up the
- linux console.
-
- To access the active Linux console via the computer's framebuffer try
- something like:
- x11vnc -rawfb console
- x11vnc -rawfb console2
-
- These will try to access the framebuffer through /dev/fb (or /dev/fb0,
- etc.) and if it succeeds it will show any text or graphics that is
- currently displayed. Keystrokes will be injected via the device
- /dev/tty0 (to force an explicit virtual terminal append a number, e.g.
- "console2" to select /dev/tty2.)
-
- If your Linux system does not have a framebuffer device (/dev/fb) you
- can get one by adding, e.g., vga=0x31B boot parameter. This enables
- the VGA framebuffer device at 1280x1024x24. 0x317 gives 1024x768x16,
- etc. You can also enable a Linux framebuffer device by modprobing a
- framebuffer driver specific to your video card.
-
- Note that this "-rawfb console" mode shows the contents of the
- hardware framebuffer, and so will show whatever is on the screen. It
- has no concept of Virtual Terminals WRT what there is to view, it
- always shows the active virtual terminal.
-
- Another mode is specific to the Linux text Virtual Terminals, it shows
- their text and colors (but no graphics) regardless of whether it is
- the active VT or not. It is available on x11vnc 0.9.7 and later.
- Enable this mode like this:
- x11vnc -rawfb vt
- x11vnc -rawfb vt2
-
- The former will select the active one, the latter the 2nd VT. x11vnc
- implements this mode by opening the current console text file
- "/dev/vcsa2" instead of "/dev/fb". In this way it provides the basic
- functionality of the LibVNCServer LinuxVNC program.
-
- The vt mode can be a useful way to try to get a machine's X server
- working remotely, e.g. you edit /etc/X11/xorg.conf and then type
- startx (or similar, e.g. gdm) in the virtual terminal. A 2nd x11vnc
- could be used to see if the X server is now working correctly.
-
- Q-114: Can I export via VNC a Webcam or TV tuner framebuffer using
- x11vnc?
-
- Yes, this is possible to some degree with the -rawfb option. There is
- no X11 involved: snapshots from the video capture device are used for
- the screen image data. See the previous FAQ on -rawfb for background.
- For best results, use x11vnc version 0.8.1 or later.
-
- Roughly, one would do something like this:
- x11vnc -rawfb snap:/dev/video@320x240x32
-
- This requires that the system allows simple read(2) access to the
- video device. This is true for video4Linux on Linux kernel 2.6 and
- later (it won't work for 2.4, you'll need a separate program to
- snapshot to a file that you point -rawfb to; ask me if it is not clear
- what to do.)
-
- The "snap:" enforces -snapfb mode which appears to be necessary. The
- read pointer for video capture devices cannot be repositioned (which
- would be needed for scanline polling), but you can read a full frame
- of data from the device.
-
- On Linux, if the Video4Linux API is present or the v4l-info(1) program
- (related to xawtv) exists in in PATH, then x11vnc can be instructed to
- try it to determine the -rawfb WxHxB parameters for you automatically.
- In this case one would just type:
- x11vnc -rawfb video
-
- or "-rawfb video1" for the 2nd video device, etc.
-
- x11vnc has also been extended to use the Video4Linux API over v4l-info
- if it is available at build time. This enables setting parameters
- (e.g. size and brightness) via x11vnc. See the description below.
- Without Video4Linux you will need to initialize the settings of the
- video device using something like xawtv or spcaview (and then hope the
- settings persist until x11vnc reopens the device.)
-
- Many video4linux drivers tend to set the framebuffer to be 24bpp (as
- opposed to 32bpp.) Since this can cause problems with VNC viewers,
- etc, the -24to32 option will be automatically imposed when in 24bpp.
-
- Note that by its very nature, video capture involves rapid change in
- the framebuffer. This is especially true for cameras where slight
- wavering in brightness is always happening. This can lead to much
- network bandwidth consumption for the VNC traffic and also local CPU
- and I/O resource usage. You may want to experiment with "dialing down"
- the framerate via the -wait, -slow_fb, or -defer options. Decreasing
- the window size and bpp also helps.
-
-
- Setting Camera/Tuner parameters via x11vnc:
-
- There is also some support for setting parameters of the capture
- device. This is done via "-rawfb video:<settings>". This could be
- useful for unattended startup at boottime, etc. Here is the -help
- description:
-
- A more sophisticated video device scheme allows initializing the
- device's settings using:
-
- -rawfb video:<settings>
-
- The prefix could also be, as above, e.g. "video1:" to specify the
- device file. The v4l API must be available for this to work.
- Otherwise, you will need to try to initialize the device with an
- external program, e.g. xawtv, spcaview, and hope they persist when
- x11vnc re-opens the device.
-
- <settings> is a comma separated list of key=value pairs. The
- device's brightness, color, contrast, and hue can be set to
- percentages, e.g. br=80,co=50,cn=44,hu=60.
-
- The device filename can be set too if needed (if it does not start
- with "video"), e.g. fn=/dev/qcam.
-
- The width, height and bpp of the framebuffer can be set via, e.g.,
- w=160,h=120,bpp=16.
-
- Related to the bpp above, the pixel format can be set via the
- fmt=XXX, where XXX can be one of: GREY, HI240, RGB555, RGB565,
- RGB24, and RGB32 (with bpp 8, 8, 16, 16, 24, and 32 respectively.)
- See http://www.linuxtv.org for more info (V4L api.)
-
- For TV/rf tuner cards one can set the tuning mode via tun=XXX where
- XXX can be one of PAL, NTSC, SECAM, or AUTO.
-
- One can switch the input channel by the inp=XXX setting, where XXX
- is the name of the input channel (Television, Composite1, S-Video,
- etc.) Use the name that is in the information about the device that
- is printed at startup.
-
- For input channels with tuners (e.g. Television) one can change
- which station is selected by the sta=XXX setting. XXX is the
- station number. Currently only the ntsc-cable-us (US cable)
- channels are built into x11vnc. See the -freqtab option below to
- supply one from xawtv. If XXX is greater than 500, then it is
- interpreted as a raw frequency in KHz.
-
- Example:
-
- -rawfb video:br=80,w=320,h=240,fmt=RGB32,tun=NTSC,sta=47
-
- one might need to add inp=Television too for the input channel to
- be TV if the card doesn't come up by default in that one.
-
- Note that not all video capture devices will support all of the
- above settings.
-
- See the -pipeinput VID option below for a way to control the
- settings through the VNC Viewer via keystrokes.
-
- As above, if you specify a "@WxHxB..." after the <settings> string
- they are used verbatim: the device is not queried for the current
- values. Otherwise the device will be queried.
-
- Also, if you supply the "-pipeinput VID" (or use "-rawfb Video")
- option you can control the settings to some degree via keystroke
- mappings, e.g. B to increase the brightness or Up arrow to change the
- TV station:
-
- For "-pipeinput VID" and you are using the -rawfb for a video
- capture device, then an internal list of keyboard mappings is used
- to set parameters of the video. The mappings are:
-
- "B" and "b" adjust the brightness up and down.
- "H" and "h" adjust the hue.
- "C" and "c" adjust the colour.
- "N" and "n" adjust the contrast.
- "S" and "s" adjust the size of the capture screen.
- "I" and "i" cycle through input channels.
- Up and Down arrows adjust the station (if a tuner)
- F1, F2, ..., F6 will switch the video capture pixel
- format to HI240, RGB565, RGB24, RGB32, RGB555, and
- GREY respectively. See -rawfb video for details.
-
- See also the -freqtab option to supply your own xawtv channel to
- frequency mappings for your country (only ntsc-cable-us is built into
- x11vnc.)
-
-
- Q-115: Can I connect via VNC to a Qt-embedded/Qt-enhanced/Qtopia
- application running on my handheld, cell phone, or PC using the Linux
- console framebuffer (i.e. not X11)?
-
- Yes, the basic method for this is the -rawfb scheme where the Linux
- console framebuffer (usually /dev/fb0) is polled and the uinput driver
- is used to inject keystrokes and mouse input. Often you will just have
- to type:
- x11vnc -rawfb console
-
- (you may need to enable the uinput driver on the system via "modprobe
- uinput; mknod /dev/input/uinput c 10 223") If this does not find the
- correct frame buffer properties figure them out or guess them and use
- something like:
- x11vnc -rawfb /dev/fb0@640x480x16
-
- Also, to force usage of the uinput injection method use "-pipeinput
- UINPUT". See the -pipeinput description for tunable parameters, etc.
-
- One problem with the x11vnc uinput scheme is that it cannot guess the
- mouse motion "acceleration" used by the windowing application (e.g.
- QWS or X11.) For X11 and Qt-embedded the acceleration is usually 2
- (i.e. a dx of 1 from the mouse yields a 2 pixel displacement of the
- mouse cursor.) The default x11vnc uses is 2, since that is often used.
- However for one Qt-embedded system we needed to do:
- x11vnc -rawfb console -pipeinput UINPUT:accel=4.0
-
- to get reasonable positioning of the mouse.
-
- Even with the correct acceleration setting there is still some drift
- (probably because of the mouse threshold where the acceleration kicks
- in) and so x11vnc needs to reposition the cursor from 0,0 about 5
- times a second. See the -pipeinput UINPUT option for tuning parameters
- that can be set (there are some experimental thresh=N tuning
- parameters as well)
-
- Currently, one can expect mouse input to be a little flakey. All in
- all, the Linux framebuffer input mechanism for Qt-embedded framebuffer
- apps is not perfect, but it is usable.
-
- If you need to create a smaller x11vnc binary for a handheld
- environment be sure to run strip(1) on it and also consider
- configuring with, e.g. "env CPPFLAGS='-DSMALL_FOOTPRINT=1' ./configure
- ..." to remove rarely used features and large texts (use 2 or 3
- instead of 1 to remove more.) Currently (Jul/2006) this can lower the
- size of the x11vnc from 1.1MB to 0.6-0.7MB.
-
- The x11vnc uinput method applies to nearly anything on the Linux
- framebuffer console, not just Qt-embedded/Qtopia. DirectFB, SDL using
- fbcon driver, SVGAlib applications can also be viewed and interacted
- with. Even a Linux X session can be viewed and interacted with without
- using X11 (and x11vnc does not have to terminate when the X server
- restarts!) The Linux Text consoles (F1-F6) also work.
-
- Note that Qt-embedded supplies its own VNC graphics driver, but it
- cannot do both the Linux console framebuffer and VNC at the same time,
- which is often what is desired from VNC.
-
- Update: We are finding some setups like Qtopia on the IPAQ do not
- allow mouse input via uinput. Please help us debug this problem by
- trying x11vnc on your device and letting us know what does and does
- not work. See the next FAQ for a possible workaround for touchscreens.
-
-
- Q-116: How do I inject touch screen input into an
- Qt-embedded/Qt-enhanced/Qtopia cell phone such as openmoko/qtmoko Neo
- Freerunner?
-
- The qtmoko project does not use X11 for the graphical display.
- Unfortunately the Linux uinput method described in the previous FAQ
- does not work because Qt is using TSLIB (touch screen library) to
- process the input and it only reads from one device (often
- /dev/input/event1) and not from the new UINPUT device that x11vnc
- creates (under -pipeinput UINPUT)
-
- So something else needs to be done. It was discovered that by simply
- writing the touchscreen events directly to /dev/input/event1 then
- input can be injected into the system. There is no x11vnc builtin mode
- for this yet (until we understand it better), but there is a working
- script provided in x11vnc/misc/qt_tslib_inject.pl. So one could use it
- this way for example:
- x11vnc ... -rawfb console -pipeinput path/to/qt_tslib_inject.pl -env INJECT_O
-PTIONS=clickonly,cal=/etc/pointercal
-
- Read the script for how to enable other options and what the above
- options mean (e.g. /etc/pointercal contains TSLIB's calibration
- parameters and are necessary to achieve accurate pointing.)
-
- The x11vnc/misc/qt_tslib_inject.pl script can potentially be modified
- to handle other devices where the uinput method fails. It could also
- be modified to create 'hot keys', etc.
-
- Please let us know how things go if you try this out; there is much to
- learn about synthetic input injection in handhelds and cell phones. As
- we learn more we can develop a builtin x11vnc mode for this sort of
- injection.
-
- Update Dec/2010: There is experimental built-in UINPUT support in the
- x11vnc development tarball for qtmoko with touchpad managed by tslib.
- See -pipeinput UINPUT for more info. Here is an example:
- x11vnc -rawfb console -pipeinput UINPUT:touch,tslib_cal=/etc/pointercal,dire
-ct_abs=/dev/input/event1,nouinput,dragskip=3
-
-
- Q-117: Now that non-X11 devices can be exported via VNC using x11vnc,
- can I build it with no dependencies on X11 header files and libraries?
-
- Yes, as of Jul/2006 x11vnc enables building for -rawfb only support.
- Just do something like when building:
- ./configure --without-x (plus any other flags)
- make
-
- You can then test via "ldd x11vnc" that the binary does not depend on
- libX11.so, etc. See the previous FAQ's for non-X11 framebuffer usage.
- If you use this for an interesting non-X11 application please let us
- know what you did.
-
-
- Q-118: How do I cross compile x11vnc for a different architecture than
- my Linux i386 or amd64 PC?
-
- You will need a cross-compiling toolchain. Perhaps your distro
- provides these or you can find a HOWTO for your distro. We found a
- nice one at qtmoko.org for building armel binaries on Debian Linux
- i386 machines. It includes most of the libraries that x11vnc needs. We
- use that example here.
-
- We ran this script to set PATH, configure, and build:
-#!/bin/sh
-
-# toolchain from: qtmoko-debian-toolchain-armv4t-eabi.tar.gz
-
-export PATH=/opt/toolchains/arm920t-eabi/bin:$PATH
-
-env CC=arm-linux-gcc ./configure --host=arm-linux --without-avahi
-
-make
-
-arm-linux-strip ./x11vnc/x11vnc
-ls -l ./x11vnc/x11vnc
-
- Note we had to include --without-avahi due to lack of
- libavahi-client.so.3 supplied by the toolchain we used. One would need
- to add it if it was desired on the target machine. We also stripped
- the binary to make it smaller.
-
- For an embedded system one may also want to add --without-x if the
- embedded system does not use X11 and the -rawfb mechanism must be
- used.
-
-
- Q-119: Does x11vnc support Mac OS X Aqua/Quartz displays natively
- (i.e. no X11 involved)?
-
- Yes, since Nov/2006 in the development tree (x11vnc-0.8.4 tarball)
- there is support for native Mac OS X Aqua/Quartz displays using the
- -rawfb mechanism described above. The mouse and keyboard input is
- achieved via Mac OS X API's.
-
- So you can use x11vnc as an alternative to OSXvnc (aka Vine Server),
- or Apple Remote Desktop (ARD). Perhaps there is some x11vnc feature
- you'd like to use on Mac OS X, etc. For a number of activities (e.g.
- window drags) it seems to be faster than OSXvnc.
-
- Notes:
-
- X11: x11vnc will also work (as it has for years) with a X11 server
- (XDarwin) running on Mac OS X (people often install this software to
- display remote X11 apps on their Mac OS X system, or use some old
- favorites locally such as xterm.) However in this case x11vnc will
- only work reasonably in single window -id windowid mode (and the
- window may need to have mouse focus.)
-
- If you do not have the DISPLAY env. variable set, x11vnc will assume
- native Aqua/Quartz on Mac OS X, however if DISPLAY is set it will
- assume an X11 connection. Use "-rawfb console" to force the native
- display (or unset DISPLAY.)
-
- Update: Leopard sets DISPLAY by default in all sessions. Since it
- starts with the string "/tmp/" x11vnc will use that to know if it
- should ignore it. Use "-display :0.0" to force it.
-
- Building: If you don't have the X11 build and runtime packages
- installed you will need to build it like this:
- (cd to the e.g. x11vnc-0.9, source directory)
- ./configure --without-x
- make
-
- Win2VNC/x2vnc: One handy use is to use the -nofb mode to redirect
- mouse and keyboard input to a nearby Mac (i.e. one to the side of your
- desk) via x2vnc or Win2VNC. See this FAQ for more info.
-
- Options: Here are the Mac OS X specific x11vnc options:
- -macnodim For the native Mac OS X server, disable dimming.
- -macnosleep For the native Mac OS X server, disable display sleep
-.
- -macnosaver For the native Mac OS X server, disable screensaver.
- -macnowait For the native Mac OS X server, do not wait for the
- user to switch back to his display.
- -macwheel n For the native Mac OS X server, set the mouse wheel
- speed to n (default 5.)
- -macnoswap For the native Mac OS X server, do not swap mouse
- buttons 2 and 3.
- -macnoresize For the native Mac OS X server, do not resize or rese
-t
- the framebuffer even if it is detected that the scree
-n
- resolution or depth has changed.
- -maciconanim n For the native Mac OS X server, set n to the number
- of milliseconds that the window iconify/deiconify
- animation takes. In -ncache mode this value will be
- used to skip the animation if possible. (default 400)
- -macmenu For the native Mac OS X server, in -ncache client-sid
-e
- caching mode, try to cache pull down menus (not perfe
-ct
- because they have animated fades, etc.)
-
- PasteBoard/Clipboard: There is a bug that the Clipboard (called
- PasteBoard on Mac it appears) exchange will not take place unless
- x11vnc was started from inside the Aqua display (e.g. started inside a
- Terminal app window.) Otherwise it cannot connect to the PasteBoard
- server. So Clipboard exchange won't work for our standard "ssh in"
- startup scheme.
-
- Hopefully this deficiency can be removed, but until then for Clipboard
- exchange to work you will need to start x11vnc inside the desktop
- session (i.e. either start it running before you leave, or start up a
- 2nd x11vnc inside from a 1st one started outside, or use the apple
- script below)
-
- Here also is a osascript trick that seems to work (it opens the
- Terminal app and instructs it to start x11vnc):
-
-#!/bin/sh
-#
-# start_x11vnc: start x11vnc in a Terminal window
-# (this will allow Clipboard/Pasteboard exchange to work)
-
-tmp=/tmp/start_x11vnc.$$
-
-cat > $tmp <<END
-
-tell application "Terminal"
- activate
- do script with command "$HOME/x11vnc -rfbauth .vnc/passwd -ssl SAVE"
-end tell
-
-END
-
-osascript $tmp
-rm -f $tmp
-
- where you should customize the x11vnc command line to your needs and
- the full path to the binary. Save it in a file e.g. "start_x11vnc" and
- then after you SSH in just type "./start_x11vnc" (or have ssh run the
- command for you.) Then once you are connected via VNC, iconify the
- Terminal windows (you can't delete them since that will kill x11vnc.)
-
- Update Aug/2010: A user reports the following useful information:
-This is not a problem on Mac OS X 10.6.x (Snow Leopard) when connecting
-via ssh to start x11vnc. And, on Mac OS X 10.5.x (Leopard), the problem
-can be permanently eliminated by doing this:
-
-
-sudo /usr/libexec/PlistBuddy -c 'delete :LimitLoadToSessionType' \
- -c 'add :LimitLoadToSessionType string Background' \
- /System/Library/LaunchAgents/com.apple.pboard.plist
-# ignore any 'Delete: Entry, ":LimitLoadToSessionType", Does Not Exist' message
-
-and then restarting (yes, you must restart not just log off). But
-ONLY do that for Mac OS X 10.5.x and NOT for 10.6.x (which doesn't
-need it anyway).
-
- We recently got access to a MacOSX 10.6.4 (Snow Leopard) macbook and
- have confirmed that the above is correct.
-
-
- Q-120: Can x11vnc be used as a VNC reflector/repeater to improve
- performance for the case of a large number of simultaneous VNC viewers
- (e.g. classroom broadcasting or a large demo)?
-
- Yes, as of Feb/2007 there is the "-reflect host:N" option to connect
- to the VNC server "host:N" (either another x11vnc or any other VNC
- server) and re-export it. VNC viewers then connect to the x11vnc(s)
- running -reflect.
-
- The -reflect option is the same as: "-rawfb vnc:host:N". See the
- -rawfb description under "VNC HOST" for more details.
-
- You can replace "host:N" with "listen" or "listen:port" for reverse
- connections.
-
- One can set up a number of such reflectors/repeaters to spread the
- resource usage around, e.g.:
- C -------<-------|
- C -------<-------|
- C -------<-------|---- R -----|
- C -------<-------| |
- C -------<-------| |
- |
- C -------<-------| |
- C -------<-------| |
- C -------<-------|---- R -----|
- C -------<-------| |
- C -------<-------| |
- |====== S
- C -------<-------| |
- C -------<-------| |
- C -------<-------|---- R -----|
- C -------<-------| |
- C -------<-------| |
- |
- C -------<-------| |
- C -------<-------| |
- C -------<-------|---- R -----|
- C -------<-------|
- C -------<-------|
-
- Where "S" is the original VNC Server, "C" denote VNC viewer clients,
- and "R" denotes an x11vnc running -reflect to "S".
-
- Ideally, a client "C" will be fairly close network-wise to its "R". It
- is fine to run the "R" on the same machine as one of its "C's". A nice
- setup for a large, (e.g. 64-128) viewer classroom broadcast case would
- be to run R's on areas isolated by network switches, e.g. one R per
- switch.
-
- In an extreme case (e.g. 1000 viewers) one might actually need a 2nd
- layer of R's in the tree. If you try something like that let us know!
-
- There are many resource savings in doing something like the above. The
- first obvious one is network bandwidth savings. Another is less CPU
- load on "S" since it handles many fewer simultaneous connections.
- Also, if there are a few clients C on very slow links, their presence
- does not slow down every other client, just the clients on their "R".
- One way a slow client affects things is if there are some large
- framebuffer writes (e.g. jpeg image region) then the repeater may
- block waiting for that large write to finish before going onto the
- next client (however, if the write is small enough, the kernel will
- buffer it and the server can go on to service the next client.)
-
- The x11vnc -reflect implementation uses the libvncclient library in
- the LibVNCServer project to handle the connection to "S". It is not
- currently very efficient since it simply does its normal framebuffer
- polling scheme on the libvncclient framebuffer (which it then
- re-exports via VNC to its clients C.) However, CopyRect and
- CursorShape encodings are preserved in the reflection and that helps.
- Dragging windows with the mouse can be a problem (especially if S is
- not doing wireframing somehow, consider -nodragging if the problem is
- severe) For a really fast reflector/repeater it would have to be
- implemented from scratch with performance in mind. See these other
- projects:
- http://sourceforge.net/projects/vnc-reflector/,
- http://www.tightvnc.com/projector/ (closed source?),
-
-
- Automation via Reverse Connections: Instead of having the R's
- connect directly to S and then the C's connect directly to the R they
- should use, some convenience can be achieved by using reverse
- connections (the x11vnc ""-connect host1,host2,..." option.) Suppose
- all the clients "C" are started up in Listen mode:
- client1> vncviewer -listen
- client2> vncviewer -listen
- client3> vncviewer -listen
- ...
- client64> vncviewer -listen
-
- (e.g. client1> is the cmdline prompt on machine client1 ... etc) and
- all the repeaters R are started like this:
- repeater1> x11vnc -reflect listen -connect client1,client2,...client8
- repeater2> x11vnc -reflect listen -connect client9,client10,...client16
- ...
- repeater8> x11vnc -reflect listen -connect client57,client58,...client64
-
- and finally the main server is started to kick the whole thing into
- motion:
- vncserver> x11vnc -display :0 -connect repeater1,repeater2,...repeater8
-
- (or instruct a non-x11vnc VNC server to reverse connect to the
- repeaters.) For a classroom broadcasting setup one might have the
- first two sets of commands start automatically at bootup or when
- someone logs in, and then start everything up with the S server. One
- may even be able to script the forward connection bootstrap case, let
- us know what you did. A really nice thing would be some sort of
- auto-discovery of your repeater, etc...
-
- Q-121: Can x11vnc be used during a Linux, Solaris, etc. system
- Installation so the Installation can be done remotely?
-
- This can be done, but it doesn't always work because it depends on how
- the OS does its install. We have to "sneak in" somehow. Note that some
- OS's have a remote install (ssh etc.) built in and so you might want
- to use that instead.
-
- Usually the OS install will have to be a network-install in order to
- have networking up during the install. Otherwise, you may have a
- (slim) chance to configure the networking manually (ifconfig(8) and
- route(8).)
-
- To avoid library dependencies problems in the typical minimal (e.g.
- busybox) installation OS it is a good idea to build a statically
- linked x11vnc binary. A way that often works is to do a normal build
- and then paste the final x11vnc link line into a shell script. Then
- change the "gcc" to "gcc -static" and run the shell script. You may
- need to disable features (e.g. "--without-xfixes") if there is not a
- static library for the feature available. You may also need to add
- extra link options (e.g. "-lXrender") to complete library dependencies
- manually.
-
- Let's call the binary x11vnc.static. Place it on a webserver
- somewhere. It may be possible to retrieve it via scp(1) too.
-
- During the install you need to get a shell to retreive x11vnc.static
- and run it.
-
- If the Solaris install is an older X-based one, there will be a menu
- for you to get a terminal window. From that window you might be able
- to retrieve x11vnc.static via wget, scp, or ftp. Remember to do "chmod
- 755 ./x11vnc.static" and then find the -auth file as in this FAQ.
-
- If it is a Linux install that uses an X server (e.g. SuSE and probably
- Fedora), then you can often get a shell by pressing Ctrl-Alt-F2 or
- similar. Then get the x11vnc binary via something like this:
- cd /tmp
- wget http://192.168.0.22/x11vnc.static
- chmod 755 ./x11vnc.static
-
- Find the name of the auth file as in this FAQ. (maybe run "ps wwaux |
- grep auth".) Then run it like this:
- ./x11vnc.static -forever -nopw -display :0 -auth /tmp/wherever/the/authfile
-
- then press Alt-F7 to go back to the X install. You should now be able
- to connect via a vnc viewer and continue the install. Watch out for
- the display being :1, etc.
-
- If there is a firewall blocking incoming connections during the
- install, use the "-connect hostname" option option for a reverse
- connection to the hostname running the VNC viewer in listen mode.
-
- Debian based installs are either console-text or console-framebuffer
- based. These are install (or expert) and installgui (or expertgui)
- boot lines, respectively. For the console-text based installs you
- probably need to add a boot cmd line option like vga=0x314 (which is
- 800x600x16) to get the console-text to use the linux framebuffer
- device properly.
-
- For a Debian console-text based install after the network is
- configured press Ctrl-Alt-F2 to get a shell. Retrieve the binary via
- wget as above and chmod 755 it. Then run it something like this:
- sleep 10; ./x11vnc.static -forever -nopw -rawfb console
-
- then before the sleep is over press Alt-F1 to get back to the install
- virtual console. You should be able to connect via a VNC viewer and
- continue with the install.
-
- For a recent (2009) Debian install we booted with "expert vga=0x301"
- and "expert vga=0x311" to get console text based installs at 640x480x8
- and 640x480x16, respectively (replace "expert" with "install" if you
- like.) Otherwise it was giving a 16 color 640x480x4 (4 bit per pixel)
- display which x11vnc could not handle.
-
- For Debian console-framebuffer GUI based installs (installgui or
- expertgui) we have not be able to enter keystrokes or mouse motions.
- This may be resolved if the install had the Linux kernel module
- uinput, but it doesn't; one can wget uinput.ko and then run insmod on
- it, but the module must match the installation kernel. So, failing
- that, you can only do the GUI view-only, which can be handy to watch a
- long network install from your desk instead of in front of the machine
- being installed. For these, after the network is configured press
- Ctrl-Alt-F2 to get a shell. Retrieve the binary via wget as above and
- chmod 755 it. Then run it something like this:
- sleep 10; ./x11vnc.static -forever -nopw -rawfb console
-
- then before the sleep is over press Alt-F5 to get back to the GUI
- install console. You should be able to connect via a VNC viewer and
- watch the install.
- [Misc: Clipboard, File Transfer/Sharing, Printing, Sound, Beeps,
- Thanks, etc.]
-
- Q-122: Does the Clipboard/Selection get transferred between the
- vncviewer and the X display?
-
- As of Jan/2004 x11vnc supports the "CutText" part of the RFB (aka VNC)
- protocol. When text is selected/copied in the X session that x11vnc is
- polling it will be sent to connected VNC viewers. And when CutText is
- received from a VNC viewer then x11vnc will set the X11 selections
- PRIMARY, CLIPBOARD, and CUTBUFFER0 to it. x11vnc is able to hold the
- PRIMARY and CLIPBOARD selections (Xvnc does not seem to do this.)
-
- The X11 selections can be confusing, especially to those coming from
- Windows or MacOSX where there is just a single 'Clipboard'. The X11
- CLIPBOARD selection is a lot like that of Windows and MacOSX, e.g.
- highlighted text is sent to the clipboard when the user activates
- "Edit -> Copy" or presses "Control+C" (and pasting it via "Edit ->
- Paste" or "Control+V".) The X11 PRIMARY selection has been described
- as 'for power users' or 'an Easter Egg'. As soon as text is
- highlighted it is set to the PRIMARY selection and so it is
- immediately ready for pasting, usually via the Middle Mouse Button or
- "Shift+Insert". See this jwz link for more information.
-
- x11vnc's default behavior is to watch both CLIPBOARD and PRIMARY and
- whenever one of them changes, it sends the new text to connected
- viewers. Note that since the RFB protocol only has a single "CutText"
- then both selections are "merged" to some degree (and this can lead to
- confusing results.) One user was confused why x11vnc was "forgetting"
- his CLIPBOARD selection and the reason was he also changed PRIMARY
- some time after he copied text to the clipboard. Usually an app will
- set PRIMARY as soon as any text is highlighted so it easy to see how
- CLIPBOARD was forgotten. Use the -noprimary described below as a
- workaround. Similarly, by default when x11vnc receives CutText it sets
- both CLIPBOARD and PRIMARY to it (this is probably less confusing, but
- could possibly lead to some failure modes as well.)
-
- You may not like these defaults. Here are ways to change the behavior:
- * If you don't want the Clipboard/Selection exchanged at all use the
- -nosel option.
- * If you want changes in PRIMARY to be ignored use the -noprimary
- option.
- * If you want changes in CLIPBOARD to be ignored use the
- -noclipboard option.
- * If you don't want x11vnc to set PRIMARY to the "CutText" received
- from viewers use the -nosetprimary option.
- * If you don't want x11vnc to set CLIPBOARD to the "CutText"
- received from viewers use the -nosetclipboard option.
-
- You can also fine-tune it a bit with the -seldir dir option and also
- -input.
-
- You may need to watch out for desktop utilities such as KDE's
- "Klipper" that do odd things with the selection, clipboard, and
- cutbuffers.
-
-
- Q-123: Can I use x11vnc to record a Shock Wave Flash (or other format)
- video of my desktop, e.g. to record a tutorial or demo?
-
- Yes, it is possible with a number of tools that record VNC and
- transform it to swf format or others. One such popular tool is
- pyvnc2swf. There are a number of tutorials (broken link?) on how to do
- this. Another option is to use the vnc2mpg that comes in the
- LibVNCServer package.
- An important thing to remember when doing this is that tuning
- parameters should be applied to x11vnc to speed up its polling for
- this sort of application, e.g. "-wait 10 -defer 10".
-
- Q-124: Can I transfer files back and forth with x11vnc?
-
- As of Oct/2005 and May/2006 x11vnc enables, respectively, the TightVNC
- and UltraVNC file transfer implementations that were added to
- libvncserver. This currently works with TightVNC and UltraVNC viewers
- (and Windows viewers only support filetransfer it appears... but they
- do work to some degree under Wine on Linux.)
-
- The SSVNC Unix VNC viewer supports UltraVNC file transfer by use of a
- Java helper program.
-
- TightVNC file transfer is off by default, if you want to enable it use
- the -tightfilexfer option.
-
- UltraVNC file transfer is off by default, to enable it use something
- like "-rfbversion 3.6 -permitfiletransfer"
- options (UltraVNC incorrectly uses the RFB protocol version to
- determine if its features are available, so x11vnc has to pretend to
- be version 3.6.) As of Sep/2006 "-ultrafilexfer" is an alias for these
- two options. Note that running as RFB version 3.6 may confuse other
- VNC Viewers.
-
- Sadly you cannot do both -tightfilexfer and -ultrafilexfer at the same
- time because the latter requires setting the version to 3.6 and
- tightvnc will not do filetransfer when it sees that version number.
-
- Also, because of the way the LibVNCServer TightVNC file transfer is
- implemented, you cannot do Tightvnc file transfer in -unixpw mode.
- However, UltraVNC file transfer does work in -unixpw (but if a client
- tries it do a filetransfer during the login process it will be
- disconnected.)
-
- IMPORTANT: please understand if -ultrafilexfer or -tightfilexfer is
- specified and you run x11vnc as root for, say, inetd or display
- manager (gdm, kdm, ...) access and you do not have it switch users via
- the -users option, then VNC Viewers that connect are able to do
- filetransfer reads and writes as *root*.
-
- The UltraVNC and TightVNC settings can be toggled on and off inside
- the gui or by -R remote control. However for TightVNC the changed
- setting only applies for NEW clients, current clients retain their
- TightVNC file transfer ability. For UltraVNC it works better, however
- if an UltraVNC client has initiated a file transfer dialog it will
- remain in effect until the dialog is closed. If you want to switch
- between UltraVNC and TightVNC file transfer in the gui or by remote
- control you will probably be foiled by the "-rfbversion 3.6" issue.
-
-
- Q-125: Which UltraVNC extensions are supported?
-
- Some of them are supported. To get UltraVNC Viewers to attempt to use
- these extensions you will need to supply this option to x11vnc:
- -rfbversion 3.6
-
- Or use -ultrafilexfer which is an alias for the above option and
- "-permitfiletransfer". UltraVNC evidently treats any other RFB version
- number as non-UltraVNC.
-
- Here are a list of the UltraVNC extensions supported by x11vnc:
- * ServerInput: "Toggle Remote Input and Remote Blank Monitor"
- * FileTransfer: "Open File Transfer..."
- * SingleWindow: "Select Single Window..."
- * TextChat: "Open Chat..."
- * 1/n Server Scaling
-
- The SSVNC Unix VNC viewer supports these UltraVNC extensions.
-
- To disable SingleWindow and ServerInput use -noultraext (the others
- are managed by LibVNCServer.) See this option too: -noserverdpms.
-
- Also, the UltraVNC repeater proxy is supported for use with reverse
- connections: "-connect repeater://host:port+ID:NNNN". Use it for both
- plaintext and SSL connections. This mode can send any string before
- switching to the VNC protocol, and so could be used with other
- proxy/gateway tools. Also, a perl repeater implemention is here:
- ultravnc_repeater.pl
-
-
- Q-126: Can x11vnc emulate UltraVNC's Single Click helpdesk mode for
- Unix? I.e. something very simple for a naive user to initiate a
- reverse vnc connection from their Unix desktop to a helpdesk
- operator's VNC Viewer.
-
- Yes, UltraVNC's Single Click (SC) mode can be emulated fairly well on
- Unix.
-
- We use the term "helpdesk" below, but it could be any sort of remote
- assistance you want to set up, e.g. something for Unix-using friends
- or family to use. This includes Mac OS X.
-
- Assume you create a helpdesk directory "hd" on your website:
- http://www.mysite.com/hd (any website that you can upload files to
- should work, although remember the user will be running the programs
- you place there.)
-
- In that "hd" subdirectory copy an x11vnc binary to be run on the Unix
- user's machine (e.g. Linux, etc) and also create a file named "vnc"
- containing the following:
-#!/bin/sh
-
-webhost="http://www.mysite.com/hd" # Your helpdesk dir URL.
-
-vnchost="ip.someplace.net" # Your host running 'vncviewer -listen'
- # It could also be your IP number. If it is
- # a router/firewall, you will need to
- # configure it to redirect port 5500 to you
-r
- # workstation running 'vncviewer -listen'
-
-dir=/tmp/vnc_helpdesk.$$ # Make a temporary working dir.
-mkdir $dir || exit 1
-cd $dir || exit 1
-
-trap "cd /tmp; rm -rf $dir" 0 2 15 # Cleans up on exit.
-
-wget $webhost/x11vnc # Fetch x11vnc binary. If multi-
-chmod 755 ./x11vnc # platform, use $webhost/`uname`/x11vnc
- # or similar.
-
-./x11vnc -connect_or_exit $vnchost -rfbport 0 -nopw
-
- with the hostnames / IP addresses customized to your case.
-
- On the helpdesk VNC viewer machine (ip.someplace.net in this example)
- you have the helpdesk operator running VNC viewer in listen mode:
- vncviewer -listen
-
- or if on Windows, etc. somehow have the VNC viewer be in "listen"
- mode.
-
- Then, when the naive user needs assistance you instruct him to open up
- a terminal window on his Unix desktop and paste the following into the
- shell:
- wget -qO - http://www.mysite.com/hd/vnc | sh -
-
- and then press Enter. You could have this instruction on a web page or
- in an email you send him, etc. This requires that the wget is
- installed on the user's Unix machine (he might only have curl or lynx,
- see below for more info.)
-
-
- So I guess this is about 3-4 clicks (start a terminal and paste) and
- pressing "Enter" instead of "single click"...
-
- See this page for some variations on this method, e.g. how to add a
- password, SSL Certificates, etc.
-
-
- If you don't have a website (there are many free ones) or don't want
- to use one you will have to email him all of the ingredients (x11vnc
- binary and a launcher script) and tell him how to run it. This could
- be easy or challenging depending on the skill of the naive unix
- user...
-
- A bit of obscurity security could be put in with a -passwd, -rfbauth
- options, etc. (note that x11vnc will require a password even for
- reverse connections.) More info here.
-
-
- Firewalls: If the helpdesk (you) with the vncviewer is behind a
- NAT/Firewall/Router the router will have to be configured to redirect
- a port (i.e. 5500 or maybe different one if you like) to the vncviewer
- machine. If the vncviewer machine also has its own host-level
- firewall, you will have to open up the port there as well.
-
- NAT-2-NAT: There is currently no way to go "NAT-2-NAT", i.e. both User
- and Helpdesk workstations behind NAT'ing Firewall/Routers without
- configuring a router to do a port redirection (i.e. on your side, the
- HelpDesk.) To avoid modifying either firewall/router, one would need
- some public (IP address reachable on the internet) redirection/proxy
- service. Perhaps such a thing exists. http://sc.uvnc.com provides this
- service for their UltraVNC Single Click users.
-
- Update: It may be possible to do "NAT-2-NAT" with a UDP tunnel such as
- http://samy.pl/pwnat/. All that is required is that both NAT firewalls
- allow in UDP packets from an IP address to which a UDP packet has
- recently been sent to. If you try it out let us know how it went.
-
-
- Very Naive Users:
-
- If it is beyond the user how to open a terminal window and paste in a
- command (you have my condolences...) you would have to somehow setup
- his Web browser to download the "vnc" file (or a script containing the
- above wget line) and prompt the user if he wants to run it. This may
- be tricky to set up (which is probably a good thing to not have the
- web browser readily run arbitrary programs downloaded from the
- internet...)
-
- One command-line free way, tested with KDE, is to name the file vnc.sh
- and then instruct the user to right-click on the link and do "Save
- Link As" to his Desktop. It will appear as an icon, probably one that
- looks like a terminal or a command line prompt. He next should
- right-click on the icon and select "Properties" and go to the
- "Permissions" tab. Then in that dialog select the checkbox "Is
- executable". He should then be able to click on the icon to launch it.
- Another option is to right-click on the icon and select "Open With ->
- Other ..." and for the name of the application type in "/bin/sh".
- Unfortunately in both cases the command output is lost and so errors
- cannot be debugged as easily. A similar thing appears to work in GNOME
- if under "Properties -> Permissions" they click on "Execute" checkbox
- for "Owner". Then when they click on the icon, they will get a dialog
- where they can select "Run in Terminal". In general for such cases, if
- it is feasible, it might be easier to ssh to his machine and set
- things up yourself...
-
-
- SSL Encrypted Helpdesk Connections:
-
- As of Apr/2007 x11vnc supports reverse connections in SSL and so we
- can do this. On the Helpdesk side (Viewer) you will need STUNNEL or
- better use the Enhanced TightVNC Viewer (SSVNC) package we provide
- that automates all of the SSL for you.
-
- To do this create a file named "vncs" in the website "hd" directory
- containing the following:
-#!/bin/sh
-
-webhost="http://www.mysite.com/hd" # Your helpdesk dir URL.
-
-vnchost="ip.someplace.net" # Your host running 'vncviewer -listen'
- # It could also be your IP number. If it is
- # a router/firewall, you will need to
- # configure it to redirect port 5500 to you
-r
- # workstation running 'vncviewer -listen'
-
-dir=/tmp/vnc_helpdesk.$$ # Make a temporary working dir.
-mkdir $dir || exit 1
-cd $dir || exit 1
-
-trap "cd /tmp; rm -rf $dir" 0 2 15 # Cleans up on exit.
-
-wget $webhost/x11vnc # Fetch x11vnc binary. If multi-
-chmod 755 ./x11vnc # platform, use $webhost/`uname`/x11vnc
- # or similar.
-
-./x11vnc -connect_or_exit $vnchost -rfbport 0 -nopw -ssl # Note -ssl option.
-
- with the hostnames or IP addresses customized to your case.
-
- The only change from the "vnc" above is the addition of the -ssl
- option to x11vnc. This will create a temporary SSL cert: openssl(1)
- will need to be installed on the user's end. A fixed SSL cert file
- could be used to avoid this (and provide some authentication; more
- info here.)
-
- The naive user will be doing this:
- wget -qO - http://www.mysite.com/hd/vncs | sh -
-
- (or perhaps even use https:// if available.)
-
- But before that, the helpdesk operator needs to have "vncviewer
- -listen" running as before, however he needs an SSL tunnel at his end.
- The easiest way to do this is use Enhanced TightVNC Viewer (SSVNC).
- Start it, and select Options -> 'Reverse VNC Connection (-listen)'.
- Then UN-select 'Verify All Certs' (this can be enabled later if you
- want; you'll need the x11vnc SSL certificate), and click 'Listen'.
-
- If you don't want to use SSVNC for the viewer, but rather set up
- STUNNEL manually instead, make a file "stunnel.cfg" containing:
-foreground = yes
-pid =
-
-[vnc]
-accept = 5500
-connect = localhost:5501
-
- and run:
- stunnel ./stunnel.cfg
-
- and then start the "vncviewer -listen 1" (i.e. 1 to correspond to the
- 5501 port.) Note that this assumes the stunnel install created a
- Server SSL cert+key, usually /etc/stunnel/stunnel.pem (not all distros
- will do this.) Also, that file is by default only readable by root, so
- stunnel needs to be run as root. If your system does not have a key
- installed or you do not want to run stunnel as root (or change the
- permissions on the file), you can use x11vnc to create one for you for
- example:
- x11vnc -sslGenCert server self:mystunnel
-
- answer the prompts with whatever you want; you can take the default
- for all of them if you like. The openssl(1) package must be installed.
- See this link and this one too for more info on SSL certs. This
- creates $HOME/.vnc/certs/server-self:mystunnel.pem, then you would
- change the "stunnel.cfg" to look something like:
-foreground = yes
-pid =
-cert = /home/myusername/.vnc/certs/server-self:mystunnel.pem
-
-[vnc]
-accept = 5500
-connect = localhost:5501
-
- In any event, with stunnel having been setup, the naive user is
- instructed to paste in and run:
- wget -qO - http://www.mysite.com/hd/vncs | sh -
-
- to pick up the vncs script this time.
-
- Of course if a man-in-the-middle can alter what the user downloads
- then all bets are off!.
-
- More SSL variations and info about certificates can be found here.
-
-
- OpenSSL libssl.so.0.9.7 problems:
-
- If you build your own stunnel or x11vnc for deployment, you may want
- to statically link libssl.a and libcrypto.a into it because Linux
- distros are currently a bit of a mess regarding which version of
- libssl is installed.
-
- You will find the details here.
-
-
- Q-127: Can I (temporarily) mount my local (viewer-side) Windows/Samba
- File share on the machine where x11vnc is running?
-
- You will have to use an external network redirection for this.
- Filesystem mounting is not part of the VNC protocol.
-
- We show a simple Samba example here.
-
- First you will need a tunnel to redirect the SMB requests from the
- remote machine to the one you sitting at. We use an ssh tunnel:
- sitting-here> ssh -C -R 1139:localhost:139 far-away.east
-
- Or one could combine this with the VNC tunnel at the same time, e.g.:
- sitting-here> ssh -C -R 1139:localhost:139 -t -L 5900:localhost:5900 far-away
-.east 'x11vnc -localhost -display :0'
-
- Port 139 is the Windows Service port. For Windows systems instead of
- Samba, you may need to use the actual IP address of the Window machine
- instead of "localhost" in the -R option (since the Windows service
- does not listen on localhost by default.)
-
- Note that we use 1139 instead of 139 on the remote side because 139
- would require root permission to listen on (and you may have a samba
- server running on it already.)
-
- The ssh -C is to enable compression, which might speed up the data
- transfers.
-
- Depending on the remote system side configuration, it may or may not
- be possible to mount the SMB share as a non-root user. Try it first as
- a non-root user and if that fails you will have to become root.
-
- We will assume the user name is "fred" and we will try to mount the
- viewer-side Windows SMB share "//haystack/pub" in
- /home/fred/smb-haystack-pub.
- far-away> mkdir -p /home/fred/smb-haystack-pub
- far-away> smbmount //haystack/pub /home/fred/smb-haystack-pub -o username=fre
-d,ip=127.0.0.1,port=1139
-
- (The 2nd command may need to be run as root.) Then run "df" or "ls -l
- /home/fred/smb-haystack-pub" to see if it is mounted properly. Consult
- the smbmount(8) and related documentation (it may require some
- fiddling to get write permissions correct, etc.) To unmount:
- far-away> smbumount /home/fred/smb-haystack-pub
-
- At some point we hope to fold some automation for SMB ssh redir setup
- into the Enhanced TightVNC Viewer (SSVNC) package we provide (as of
- Sep 2006 it is there for testing.)
-
-
- Q-128: Can I redirect CUPS print jobs from the remote desktop where
- x11vnc is running to a printer on my local (viewer-side) machine?
-
- You will have to use an external network redirection for this.
- Printing is not part of the VNC protocol.
-
- We show a simple Unix to Unix CUPS example here. Non-CUPS port
- redirections (e.g. LPD) should also be possible, but may be a bit more
- tricky. If you are viewing on Windows SMB and don't have a local cups
- server it may be trickier still (see below.)
-
- First you will need a tunnel to redirect the print requests from the
- remote machine to the one you sitting at. We use an ssh tunnel:
- sitting-here> ssh -C -R 6631:localhost:631 far-away.east
-
- Or one could combine this with the VNC tunnel at the same time, e.g.:
- sitting-here> ssh -C -R 6631:localhost:631 -t -L 5900:localhost:5900 far-away
-.east 'x11vnc -localhost -display :0'
-
- Port 631 is the default CUPS port. The above assumes you have a Cups
- server running on your viewer machine (localhost:631), if not, use
- something like my-cups-srv:631 (the viewer-side Cups server) in the -R
- instead.
-
- Note that we use 6631 instead of 631 on the remote side because 631
- would require root permission to listen on (and you likely have a cups
- server running on it already.)
-
- Now the tricky part: to get applications to notice your cups
- server/printer on localhost:6631.
-
- If you have administrative privilege (i.e. root password) on the
- x11vnc side where the desktop is running, it should be easy to add the
- printer through some configuration utility (e.g. in KDE: Utilities ->
- Printing -> Printing Manager, and then supply admin password, and then
- Add Printer/Class, and then fill in the inquisitive wizard. Most
- important is the "Remote IPP server" panel where you put in localhost
- for Host and 6631 for Port.) The main setting you want to convey is
- the host is localhost and the port is non-standard (e.g. 6631.) Some
- configuration utilities will take an Internet Printing Protocol (IPP)
- URI, e.g. http://localhost:6631/printers/,
- ipp://localhost:6631/printers/printer-name,
- ipp://localhost:6631/ipp/printer-name, etc. Check your CUPS
- documentation and admin interfaces to find what the syntax is and what
- the "printer name" is.
-
- If you do not have root or print admin privileges, but are running a
- recent (version 1.2 or greater) of the Cups client software, then an
- easy way to temporarily switch Cups servers is to create the directory
- and file: $HOME/.cups/client.conf on the remote side with a line like:
- ServerName localhost:6631
-
- When not using x11vnc for remote access you can comment the above line
- out with a '#' (or rename the client.conf file), to have normal cups
- operation.
-
- Unfortunately, running applications may need to be restarted to notice
- the new printers (libcups does not track changes in client.conf.)
- Depending on circumstances, a running application may actually notice
- the new printers without restarting (e.g. no print dialog has taken
- place yet, or there are no CUPS printers configured on the remote
- side.)
-
- Cups client software that is older (1.1) does not support appending
- the port number, and for newer ones there is a bug preventing it from
- always working (fixed in 1.2.3.) Kludges like these at the command
- line will work:
- far-away> env CUPS_SERVER=localhost IPP_PORT=6631 lpstat -p -d
- far-away> env CUPS_SERVER=localhost IPP_PORT=6631 lpr -P myprinter file.ps
- far-away> env CUPS_SERVER=localhost IPP_PORT=6631 firefox
-
- but are somewhat awkward since you have to retroactively set the env.
- var IPP_PORT. Its value cannot be broadcast to already running apps
- (like the $HOME/.cups/client.conf trick sometimes does.) A common
- workaround for an already running app is to somehow get it to "Print
- To File", e.g. file.ps and then use something like the lpr example
- above. Also, the option "-h host:port" works with CUPS lp(1) and
- lpr(1).
-
- You can also print to Windows shares printers in principle. You may do
- this with the smbspool(8) command, or configure the remote CUPS via
- lpadmin(8), etc, to use a printer URI something like
- smb://machine:port/printer (this may have some name resolution
- problems WRT localhost.) Also, as with SMB mounting, the port redir
- (-R) to the Windows machine must use the actual IP address instead of
- "localhost".
-
- At some point we hope to fold some automation for CUPS ssh redir setup
- into the Enhanced TightVNC Viewer (SSVNC) package we provide (as of
- Sep 2006 it is there for testing.)
-
-
- Q-129: How can I hear the sound (audio) from the remote applications
- on the desktop I am viewing via x11vnc?
-
- You will have to use an external network audio mechanism for this.
- Audio is not part of the VNC protocol.
-
- We show a simple Unix to Unix esd example here (artsd should be
- possible too, we have also verified the esd Windows port works for the
- method described below.)
-
- First you will need a tunnel to redirect the audio from the remote
- machine to the one you sitting at. We use an ssh tunnel:
- sitting-here> ssh -C -R 16001:localhost:16001 far-away.east
-
- Or one could combine this with the VNC tunnel at the same time, e.g.:
- sitting-here> ssh -C -R 16001:localhost:16001 -t -L 5900:localhost:5900 far-a
-way.east 'x11vnc -localhost -display :0'
-
- Port 16001 is the default ESD uses. So when an application on the
- remote desktop makes a sound it will connect to this tunnel and be
- redirected to port 16001 on the local machine (sitting-here in this
- example.) The -C option is an attempt to compress the audio a little
- bit.
-
- So we next need a local (sitting-here) esd daemon running that will
- receive those requests and play them on the local sound device:
- sitting-here> esd -promiscuous -port 16001 -tcp -bind 127.0.0.1
-
- See the esd(1) man page for the meaning of the options (the above are
- not very secure.) (This method also works with the EsounD windows port
- esd.exe)
-
- To test this sound tunnel, we use the esdplay program to play a simple
- .wav file:
- far-away> esdplay -s localhost:16001 im_so_happy.wav
-
- If you hear the sound (Captain Kirk in this example), that means you
- are in great shape.
-
- To run individual audio applications you can use the esddsp(1)
- command:
- far-away> esddsp -s localhost:16001 xmms
-
- Then you could try playing some sounds inside xmms. You could also set
- the environment variable ESPEAKER=localhost:16001 to not need to
- supply the -s option all the time. (for reasons not clear, sometimes
- esddsp can figure it out on its own.) All the script esddsp does is to
- set ESPEAKER and LD_PRELOAD for you so that when the application opens
- the sound device (usually /dev/dsp) its interactions with the device
- will be intercepted and sent to the esd daemon running on sitting-here
- (that in turn writes them to the real, local /dev/dsp.)
-
- Redirecting All sound:
-
- It does not seem to be possible to switch all of the sound of the
- remote machine from its sound device to the above esd+ssh tunnel
- without some preparation. But it can be done reasonably well if you
- prepare (i.e. restart) the desktop with this in mind.
-
- Here is one way to redirect all sound. The idea is we run the entire
- desktop with sound directed to localhost:16001. When we are sitting at
- far-away.east we run "esd -promiscuous -port 16001 -tcp -bind
- 127.0.0.1" on far-away.east (to be able to hear the sound.) However,
- when we are sitting at sitting-here.west we kill that esd process and
- run that same esd command on sitting-here.west and start up the above
- ssh tunnel. This is a little awkward, but with some scripts one would
- probably kill and restart the esd processes automatically when x11vnc
- is used.
-
- So next we have to run the whole desktop pointing toward our esd. Here
- is a simple way to test. Log in to the machine via the "FailSafe"
- desktop. Then in the lone terminal type something like:
- esddsp -s localhost:16001 gnome-session
-or:
- esddsp -s localhost:16001 startkde
-
- where the last part is whatever command starts your desktop (even
- fvwm2.) This causes the environment variables ESPEAKER and LD_PRELOAD
- to be set appropriately and every application (processes with the
- desktop as an ancestor) will use them. If this scheme works well you
- can make it less klunky by adding the command to your ~/.xsession,
- etc. file that starts your default desktop. Or you may be able to
- configure your desktop to use localhost:16001, or whatever is needed,
- via a gui configuration panel. Some Notes:
- * Not all audio applications are compatible with the esd and artsd
- mechanisms, but many are.
- * The audio is not compressed so you probably need a broadband or
- faster connection. Listening to music may not be very pleasant...
- (Although we found streaming music from across the US over cable
- modem worked OK, but took 200 KB/sec, to use less bandwidth
- consider something like "ssh far-away.east 'cat favorite.mp3' |
- mpg123 -b 4000 -")
- * Linux does not seem to have the concept of LD_PRELOAD_64 so if you
- run on a mixed 64- and 32-bit ABI system (e.g. AMD x86_64) some of
- the applications will fail to run because LD_PRELOAD will point to
- libraries of the wrong wordsize.
- * At some point we hope to fold some automation for esd or artsd ssh
- redir setup into the Enhanced TightVNC Viewer (SSVNC) package we
- provide (as of Sep/2006 it is there for testing.)
-
-
- Q-130: Why don't I hear the "Beeps" in my X session (e.g. when typing
- tput bel in an xterm)?
-
- As of Dec/2003 "Beep" XBell events are tracked by default. The X
- server must support the XKEYBOARD extension (this is not on by default
- in Solaris, see Xserver(1) for how to turn it on via +kb), and so you
- won't hear them if the extension is not present.
-
- If you don't want to hear the beeps use the -nobell option. If you
- want to hear the audio from the remote applications, consider trying a
- redirector such as esd.
-
-
- Q-131: Does x11vnc work with IPv6?
-
- Update: as of Apr/2010 in the 0.9.10 x11vnc development tarball, there
- is now built-in support for IPv6 (128 bit internet addresses.) See the
- -6 and -connect options for details.
-
- The remainder of this FAQ entry shows how to do with this with pre
- 0.9.10 x11vnc using IPv6 helper tools.
- _________________________________________________________________
-
- Using an external IPv6 helper:
- A way to do this is via a separate helper program such as inetd (or
- for encrypted connections: ssh or stunnel.) For example, you configure
- x11vnc to be run from inetd or xinetd and instruct it to listen on an
- IPv6 address. For xinetd the setting "flags = IPv6" will be needed.
- For inetd.conf, an example is:
- 5900 stream tcp6 nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc_wrapper.sh
-
- We also provide a transitional tool in "x11vnc/misc/inet6to4" that
- acts as a relay for any IPv4 application to allow connections over
- IPv6. For example:
- inet6to4 5900 localhost:5900
-
- where x11vnc is listening on IPv4 port 5900.
-
- Also note that not all VNC Viewers are IPv6 enabled, so a redirector
- may also be needed for them. The tool "inet6to4 -r ..." can do this as
- well. SSVNC (see below) supports IPv6 without need for the helper.
-
- # ./inet6to4 -help
-
- inet6to4: Act as an ipv6-to-ipv4 relay for tcp applications that
- do not support ipv6.
-
- Usage: inet6to4
- inet6to4 -r
-
- Examples: inet6to4 5900 localhost:5900
- inet6to4 8080 web1:80
- inet6to4 -r 5900 fe80::217:f2ff:fee6:6f5a%eth0:5900
-
- The -r option reverses the direction of translation (e.g. for ipv4
- clients that need to connect to ipv6 servers.) Reversing is the default
- if this script is named 'inet4to6' (e.g. by a symlink.)
-
- Use Ctrl-C to stop this program.
-
- You can also set env. vars INET6TO4_LOOP=1 or INET6TO4_LOOP=BG
- to have an outer loop restarting this program (BG means do that
- in the background), and INET6TO4_LOGFILE for a log file.
- Also set INET6TO4_VERBOSE to verbosity level and INET6TO4_WAITTIME
- and INET6TO4_PIDFILE (see below.)
-
- The "INET6TO4_LOOP=BG" and "INET6TO4_LOGFILE=..." env. variables make
- the tool run reliably as a daemon for very long periods. Read the top
- part of the script for more information.
- _________________________________________________________________
-
- Encrypted Tunnels with IPv6 Support:
- For SSH tunnelled encrypted VNC connections, one can of course use the
- IPv6 support in ssh(1).
-
- For SSL encrypted VNC connections, one possibility is to use the IPv6
- support in stunnel(1). This includes the built-in support via the
- -stunnel option. For example:
- x11vnc -stunnel SAVE -env STUNNEL_LISTEN=:: -env STUNNEL_DEBUG=1 ...
- _________________________________________________________________
-
- SSH IPv6 Tricks:
- It is interesting to note that ssh(1) can do basically the same thing
- as inet6to4 above by:
- ssh -g -L 5900:localhost:5901 localhost "printf 'Press Enter to Exit: '; read
- x"
-
- (where we have x11vnc running via "-rfbport 5901" in this case.)
-
- Note that one can also make a home-brew SOCKS5 ipv4-to-ipv6 gateway
- proxy using ssh like this:
- ssh -D '*:1080' localhost "printf 'Press Enter to Exit: '; read x"
-
- then specify a proxy like socks://hostname:1080 where hostname is the
- machine running the above ssh command (add -v to ssh for connection
- logging info.)
- _________________________________________________________________
-
- IPv6 SSVNC Viewer:
- Our SSVNC VNC Viewer is basically a wrapper for ssh(1) and stunnel(1),
- and so it already has good IPv6 support because these two commands do.
- On Unix, MacOSX, and Windows nearly all of the the remaining parts of
- SSVNC (e.g. the built-in proxying and un-encrypted connections) have
- been modified to support IPv6 in SSVNC 1.0.26.
-
-
-
-
-
-
- Contributions:
-
- Q-132: Thanks for your program or for your help! Can I make a
- donation?
-
- Please do (any amount is appreciated; very few have donated) and thank
- you for your support! Click on the PayPal button below for more info.
-
- [x-click-but04.gif]-Submit
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/chainingssh.html:
-
-
- _________________________________________________________________
-
- Chaining ssh's: Note that for use of a ssh gateway and -L redirection
- to an internal host (e.g. "-L 5900:otherhost:5900") the VNC traffic
- inside the firewall is not encrypted and you have to manually log into
- otherhost to start x11vnc. Kyle Amon shows a method where you chain
- two ssh's together that encrypts all network traffic and also
- automatically starts up x11vnc on the internal workstation:
-#!/bin/sh
-#
-gateway="example.com" # or "user@example.com"
-host="labyrinth" # or "user@hostname"
-user="kyle"
-
-# Need to sleep long enough for all of the passwords and x11vnc to start up.
-# The </dev/null below makes the vncviewer prompt for passwd via popup window.
-#
-(sleep 10; vncviewer -encodings "copyrect tight zrle zlib hextile" \
- localhost:0 </dev/null >/dev/null) &
-
-# Chain the vnc connection thru 2 ssh's, and connect x11vnc to user's display:
-#
-exec /usr/bin/ssh -t -L 5900:localhost:5900 $gateway \
- /usr/bin/ssh -t -L 5900:localhost:5900 $host \
- sudo /usr/bin/x11vnc -localhost -auth /home/$user/.Xauthority \
- -rfbauth .vnc/passwd -display :0
-
- Also note the use of sudo(1) to switch to root so that the different
- user's .Xauthority file can be accessed. See the visudo(8) manpage for
- details on how to set this up (remove the sudo if you do not want to
- do this). One can also chain together ssh's for reverse connections
- with vncviewers using the -listen option. For this case -R would
- replace the -L (and 5500 the 5900, see the #2 example script above).
- If the gateway machine's sshd is configured with GatewayPorts=no (the
- default) then the double chaining of "ssh -R ..." will be required for
- reverse connections to work.
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/miscbuild.html:
-
-
- _________________________________________________________________
-
- Misc. Build problems: We collect here rare build problems some users
- have reported and the corresponding workarounds. See also the FAQ's on
- building.
- _________________________________________________________________
-
- ENV parameter: One user had a problem where the build script below was
- failing because his work environment had the ENV variable set to a
- script that was resetting his PATH so that gcc could no longer be
- found. Make sure you do not have any ENV or BASH_ENV in your
- environment doing things like that. Typing "unset ENV", etc. before
- configuring and building should clear it.
- _________________________________________________________________
-
- Bash xpg: One user had his bash shell compiled with
- --enable-xpg-echo-default that causes some strange behavior with
- things like echo "\\1 ..." the configure script executes. In
- particular instead of getting "\1" the non-printable character "^A" is
- produced, and causes failures at compile time like:
- ../rfb/rfbconfig.h:9:22: warning: extra tokens at end of #ifndef directive
-
- The workaround is to configure like this:
- env CONFIG_SHELL=/bin/sh /bin/sh ./configure
-
- i.e. avoid using the bash with the misbehavior. A bug has been filed
- against autoconf to guard against this.
- _________________________________________________________________
-
- AIX: one user had to add the "X11.adt" package to AIX to get build
- header files like XShm.h, etc.
- _________________________________________________________________
-
- Ubuntu Feisty Fawn 7.04: In May/2007 one user said he needed to add
- these packages to compile x11vnc on that Linux distro and version:
- apt-get install build-essential make bin86 libjpeg62-dev libssl-dev libxtst-d
-ev
-
- Note that Ubuntu is based on Debian, so perhaps this is the list
- needed on Debian (testing?) as well. To build in Avahi (mDNS service
- advertising) support it would appear that libavahi-client-dev is
- needed as well.
- _________________________________________________________________
-
- Exceedingly slow compilation: x11vnc has a couple of files which
- contain very large "case statements" (over 100 cases) that on some
- platforms can take a very long time to compile (in extreme cases over
- an hour). However on 32bit Linux with intel/amd processor and gcc
- these files usually take less than 10 seconds to compile. For 64bit
- systems using gcc the problem appears to be much worse.
-
- The two files with the large number of cases, remote.c and x11vnc.c,
- have no real need to be optimized (the code is used only very
- infrequently). So it is fine to supply "-O0" (disables optimization)
- to CFLAGS when compiling them. However, it is tricky with
- autoconf/automake to do this (especially since both the compiler and
- make versions have a big effect).
-
- So if the compile times are getting too long for you for these two
- files you will need to manually change some things. First, run
- configure and when it has finished, edit the generated file
- x11vnc/Makefile and put these lines at the very top:
-x11vnc-x11vnc.o : CFLAGS += -O0
-x11vnc-remote.o : CFLAGS += -O0
-
- Those lines assume gnu make (gmake) is being used. If you are using
- another make, say Solaris make, insert these instead:
-x11vnc-x11vnc.o := CFLAGS += -O0
-x11vnc-remote.o := CFLAGS += -O0
-
- You could write a build shell script that modified the Makefile this
- way before running make.
-
- The "-O0" (note it is "capital Oh" followed by "zero") assumes the gcc
- compiler. If you are using a different compiler you will need to find
- the command line option to disable optimization, or otherwise have the
- lines set CFLAGS to the empty string.
- _________________________________________________________________
-
- Broken Thread Local Storage on SuSE 9.2: Starting with x11vnc 0.9.8
- the bundled libvncserver uses the __thread keyword to make some of the
- encodings (i.e. tight) thread safe (multiple VNC clients can be using
- tight at the same time in x11vnc -threads mode.) Evidently on the old
- SuSE 9.2 system the compiler does not support the thread local storage
- properly. Here is an example build failure:
-tight.c:1126: error: unrecognizable insn:
-(insn:HI 11 10 13 0 (nil) (set (reg/f:SI 59)
- (const:SI (plus:SI (symbol_ref:SI ("%lpalette"))
- (const_int 2048 [0x800])))) -1 (nil)
- (expr_list:REG_EQUAL (const:SI (plus:SI (symbol_ref:SI ("%lpalette"))
- (const_int 2048 [0x800])))
- (nil)))
-tight.c:1126: internal compiler error: in extract_insn, at recog.c:2175
-Please submit a full bug report,
-with preprocessed source if appropriate.
-See URL:http://www.suse.de/feedback for instructions.
-
- The workaround is to disable thread local storage at configure time
- like this:
-env CPPFLAGS="-DTLS=''" ./configure
-
- and then build it.
- _________________________________________________________________
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/sunray.html:
-
-
- Sun Ray Notes:
-
- You can run x11vnc on your (connected or disconnected) SunRay session
- (Please remember to use settings like -wait 200, -sb 15, and not
- running a screensaver animation (blank instead) to avoid being a
- resource hog! x11vnc does induce a lot of memory I/O from polling the
- X server. It also helps to have a solid background color, e.g.
- -solid).
-
- News: Sun Ray Remote Control Toolkit: See the nice set of tools in the
- Sun Ray Remote Control Toolkit that launch x11vnc automatically for
- you for certain usage modes.
-
- You have to know the name of the machine your SunRay session X server
- is running on (so you can ssh into it and start x11vnc). You also need
- to know the X11 DISPLAY number for the session: on a SunRay it could
- be a large number, e.g. :137, since there are many people with X
- sessions (Xsun processes) on the same machine. If you don't know it,
- you can get it by running who(1) in a shell on the SunRay server and
- looking for the dtlocal entry with your username (and if you don't
- even know which server machine has your session, you could login to
- all possible ones looking at the who output for your username...).
-
- I put some code in my ~/.dtprofile script that stores $DISPLAY
- (including the hostname) in a ~/.sunray_current file at session
- startup (and deletes it when the X session ends) to make it easy to
- get at the hostname and X11 display number info for my current X
- sessions when I ssh in and am about to start x11vnc.
-
- SunRay Gotcha #1: Note that even though your SunRay X11 DISPLAY is
- something like :137, x11vnc still tries for port 5900 as its listening
- port if it can get it, in which case the VNC display (i.e. the
- information you supply to the VNC viewer) is something like
- sunray-server:0 (note the :0 corresponding to port 5900, it is not
- :137). If it cannot get 5900, it tries for 5901, and so on. You can
- also try to force the port (and thereby the VNC display) using the
- -rfbport NNNN option.
-
- Especially on a busy Sun Ray server it is often difficult to find free
- ports for both VNC and the HTTP Java applet server to listen on. This
- script, vnc_findports may be of use for doing this automatically. It
- suggests x11vnc command line options based on netstat output that
- lists the occupied ports. It is even more difficult to start
- vncserver/Xvnc on a busy Sun Ray because then 3 ports (HTTP, VNC, and
- X11), all separated by 100 are needed! This script, findvncports may
- be helpful as well. Both scripts start at VNC display :10 and work
- their way up.
-
- SunRay Gotcha #2: If you get an error like:
- shmget(tile) failed.
- shmget: No space left on device
-
- when starting up x11vnc that most likely means all the shared memory
- (shm) slots are filled up on your machine. The Solaris default is only
- 100, and that can get filled up in a week or so on a SunRay server
- with lots of users. If the shm slot is orphaned (e.g. creator process
- dies) the slot is not reclaimed. You can view the shm slots with the
- "ipcs -mA" command. If there are about 100 then you've probably hit
- this problem. They can be cleaned out (by the owner or by root) using
- the ipcrm command. I wrote a script shm_clear that finds the orphans
- and lists or removes them. Longer term, have your SunRay sysadmin add
- something like this to /etc/system:
- set shmsys:shminfo_shmmax = 0x2000000
- set shmsys:shminfo_shmmni = 0x1000
-
- SunRay Gotcha #3: Some SunRay installations have implemented
- suspending certain applications when a SunRay session is in a
- disconnected state (e.g. Java Badge pulled out, utdetach, etc). This
- is a good thing because it limits hoggy or runaway apps from wasting
- the shared CPU resource. Think how much CPU and memory I/O is wasted
- by a bunch of Firefox windows running worthless Flash animations while
- your session is disconnected!
-
- So some sites have implemented scripts to suspend (e.g. kill -STOP)
- certain apps when your badge is removed from the SunRay terminal. When
- you reattach, it kill -CONT them. This causes problems for viewing the
- detached SunRay session via x11vnc: those suspended apps will not
- respond (their windows will be blank or otherwise inactive).
-
- What to do? Well, since you are going to be using the application you
- might as well unfreeze it rather than starting up a 2nd instance. Here
- is one way to do it using the kill -CONT mechanism:
- kill -CONT `ps -ealf | grep ' T ' | grep $LOGNAME | awk '{print $4}'`
-
- If you want to be a good citizen and re-freeze them before you exit
- x11vnc this script could be of use:
-#!/bin/sh
-#
-# kill -STOP/-CONT script for x11vnc (or other) SunRay usage ("freezes"
-# certain apps from hogging resources when disconnected).
-#
-# Put here a pattern that matches the apps that are frozen:
-#
-appmatch="java_vm|jre|netscape-bin|firefox-bin|realplay|acroread|mozilla-bin"
-
-if [ "X$1" = "Xfreeze" ]; then
- pkill -STOP -U $LOGNAME "$appmatch"
-elif [ "X$1" = "Xthaw" ]; then
- pkill -CONT -U $LOGNAME "$appmatch"
-
-elif [ "$RFB_MODE" = "afteraccept" -a "$RFB_STATE" = "NORMAL" ]; then
- # a valid x11vnc login.
- if [ "$RFB_CLIENT_COUNT" = "1" ]; then
- # only one client present.
- pkill -CONT -U $LOGNAME "$appmatch"
- fi
-elif [ "$RFB_MODE" = "gone" -a "$RFB_STATE" = "NORMAL" ]; then
- # a valid x11vnc login.
- if [ "$RFB_CLIENT_COUNT" = "0" ]; then
- # last client present has just left.
- pkill -STOP -U $LOGNAME "$appmatch"
- fi
-fi
-exit 0
-
- If you called the script "goodcitizen" you could type "goodcitizen
- thaw" to unfreeze them, and then "goodcitizen freeze" to refreeze
- them. One could also use these x11vnc options "-afteraccept
- goodcitizen -gone goodcitizen" to do it automatically.
-
- SunRay Gotcha #4: Recent versions of the Sun Ray Server Software
- SRSS (seems to be version 3.0 or 3.1) have a "misfeature" that when
- the session is disconnected (i.e. badge/smartcard out) the screen
- locker (xscreensaver) will freeze the X server just when the "Enter
- Password" dialog box appears. So you cannot unlock the screen remotely
- via x11vnc!
-
- Update: please see Bob Doolittle's detailed description of the this
- issue at the bottom of this section.
-
- Here "freeze" means "stop other X clients from inserting keyboard and
- mouse input and from viewing the current contents of the screen". Or
- something like that; the upshot is x11vnc can't do its normal thing.
-
- There are several workarounds for this.
-
- 1) The easiest one by far is to put these lines in your
- $HOME/.dtprofile file:
-SUN_SUNRAY_UTXLOCK_PREF="/usr/openwin/bin/xlock -mode blank"
-export SUN_SUNRAY_UTXLOCK_PREF
-
- One might argue that xlock isn't particularly "pretty". (Just IMHO,
- but if something like this not being pretty actually gets in the way
- of your work I think some introspection may be in order. :-)
-
- 2) The problem has been traced to the pam_sunray.so PAM module.
- Evidently xscreensaver invokes this pam module and it communicates
- with utsessiond who in turn instructs the Xsun server to not process
- any synthetic mouse/keyboard input or to update the screen
- framebuffer. It is not clear if this is by design (security?) or
- something else.
-
- In any event, the problem can be avoided, somewhat drastically, by
- commenting out the corresponding line in /etc/pam.conf:
-#xscreensaver auth sufficient /opt/SUNWut/lib/pam_sunray.so syncondisplay
-
- Leave the other xscreensaver pam authentication lines unchanged. The
- dtsession-SunRay line may also need to be commented out to avoid the
- problem for CDE sessions. N.B. it is possible the application of a
- SSRS patch, etc, may re-enable that /etc/pam.conf line. It may be
- difficult to convince a sysadmin to make this change.
-
- 3) A more forceful way is to kill the xscreensaver process from a
- shell prompt whenever you connect via x11vnc and the screen is in a
- locked state:
-pkill -U $LOGNAME '^xscreensaver$'
-
- And then after you are in be sure to restart it by typing something
- like:
-xscreensaver &
-
- You may want to avoid restarting it until you are about to disconnect
- your VNC viewer (since if it locks the screen while you are working
- you'll be stuck again).
-
- 3') The above idea can be done a bit more cleanly by having x11vnc do
- it. Suppose we called the following script xss_killer:
-#!/bin/sh
-#
-# xss_killer: kill xscreensaver after a valid x11vnc client logs in.
-# Restart xscreensaver and lock it when the last client
-# disconnects.
-
-PATH=/usr/openwin/bin:/usr/bin:$PATH
-export PATH
-
-if [ "$RFB_MODE" = "afteraccept" -a "$RFB_STATE" = "NORMAL" ]; then
- # a valid x11vnc login.
- if [ "$RFB_CLIENT_COUNT" = "1" ]; then
- # only one client present.
- pkill -U $LOGNAME '^xscreensaver$'
- pkill -KILL -U $LOGNAME -f xscreensaver/hacks
- fi
-elif [ "$RFB_MODE" = "gone" -a "$RFB_STATE" = "NORMAL" ]; then
- # a valid x11vnc login.
- if [ "$RFB_CLIENT_COUNT" = "0" ]; then
- # last client present has just left.
- xscreensaver -nosplash &
- sleep 1
- xscreensaver-command -lock &
- fi
-fi
-
- Then we would run x11vnc with these options: "-afteraccept xss_killer
- -gone xss_killer". The -afteraccept option (introduced in version 0.8)
- is used to run a command after a vncviewer has successfully logged in
- (note that this is a VNC login, not a Unix login, so you may not want
- to do this if you are really paranoid...)
-
- Note if you use the above script and also plan to Ctrl-C (SIGINT)
- x11vnc you have to run the xscreensaver in a new process group to
- avoid killing it as well. One way to do this is via this kludge:
-perl -e 'setpgrp(0,0); exec "xscreensaver -nosplash &"'
-
- in the above script.
-
- 4) There appears to be a bug in pam_sunray.so in that it doesn't seem
- to honor the convention that, say, DISPLAY=unix:3 means to use Unix
- sockets to connect to display 3 on the local machine (this is a bit
- faster than TCP sockets). Rather, it thinks the display is a non-local
- one to a machine named "unix" (that usually does not resolve to an IP
- address).
-
- Amusingly, this can be used to bypass the pam_sunray.so blocking of
- Xsun that prevents one from unlocking the screen remotely via x11vnc.
- One could put something like this in $HOME/.dtprofile to kill any
- existing xscreensavers and then start up a fresh xscreensaver using
- DISPLAY=unix:N
-# stop/kill any running xscreensavers (probably not running yet, but to be sure
-)
-xscreensaver-command -exit
-pkill -U $LOGNAME '^xscreensaver$'
-env DISPLAY=`echo $DISPLAY | sed -e 's/^.*:/unix:/'` xscreensaver &
-
-
- Important: Note that all of the above workarounds side-step the
- pam_sunray.so PAM module in one way or another. You'll need to see if
- that is appropriate for your site's SunRay / smartcard usage. Also,
- these hacks may break other things and so you may want to test various
- scenarios carefully. E.g. check corner cases like XDMCP/dtremote,
- NSCM, etc.
-
-
- Update May 2008: Here is a useful description of this issue from Bob
- Doolittle who is a developer for Sun Ray at Sun. I don't have the time
- to digest and distill it and then adjust the above methods to provide
- a clearer description, so I just include below the description he sent
- me with the hope that it will help some users:
-
- In SRSS 4.0 and earlier, the purpose of pam_sunray.so in the "auth"
- PAM stack of screensavers is to enable NSCM (and, although this is
- much less commonly used, "SC", which is configured when 3rd-party
- software is installed to allow smartcards to be used as part of the
- authentication process) to work. It should have no effect with
- smartcards. Currently, however, it does block the PAM stack for all
- sessions, which causes xscreensaver, when it locks a disconnected
- session, to not process any mouse or keyboard events as you
- describe (unless xscreensaver does an X server grab, however, other
- applications should still be able to draw in the session although
- xscreensaver may be playing tricks like putting a black window on
- top of everything). In both of the NSCM and SC models,
- authentication occurs in a separate session before SRSS will
- reconnect to the user session, in which case pam_sunray.so causes
- xscreensaver to just unlock the screen without prompting the user
- to enter their password again. To do this, pam_sunray.so has to
- block until the session becomes reconnected, so it can query SRSS
- at that time to determine whether the user has already
- authenticated or not. In SRSS 4.0 and earlier releases,
- pam_sunray.so could have been optimized to not block smartcard
- sessions, although since the session is disconnected this typically
- isn't important (except in the x11vnc case, as you've observed).
-
- In SRSS 4.1, however, for increased security the out-of-session
- authentication model has been extended to *all* session types, so
- pam_sunray.so will be required in all cases unless users are
- willing to authenticate twice upon hotdesking (e.g. when their card
- is inserted). In future, we may do away with pam_sunray.so, and in
- fact with any traditional screen locker in the user session, since
- SRSS itself will be providing better security than a screen locker
- running entirely within the user's X session is capable of
- providing.
-
- Your trick of setting DISPLAY to unix:DPY will effectively disable
- pam_sunray.so (I'm not sure I'd call that a bug - you're going out
- of your way to do something that wouldn't occur in the normal
- course of events, and really provides no useful value other than to
- tickle this behavior in pam_sunray.so). This will mean that, in
- SRSS 4.0 and earlier releases, users will be prompted for their
- passwords twice when reconnecting to their sessions for NSCM and SC
- session types. In 4.1, disabling pam_sunray.so in this way will
- cause this double-authentication to occur for *all* sessions,
- including simple smartcard sessions. Users may be willing to pay
- that price in order to be able to use x11vnc in disconnected
- sessions. I like this hack, personally. It's a little less
- convenient than some of the other approaches you describe, but it's
- lighter-weight and more secure than most of the other approaches,
- and provides the value of being able to use x11vnc in locked
- sessions.
-
- Here are some other minor notes: - I wouldn't recommend storing
- your display in your .dtprofile, unless you're willing to live with
- a single session at a time. Personally, I often find myself using
- several sessions, in several FoGs, for short periods of time so
- this would certainly break. IMO it's pretty easy to use $DISPLAY to
- do what you want on the fly, as needed, so I don't think the price
- of breaking multiple-session functionality would be worth the
- convenience, to me at least. Here's some ksh/bash syntax to extract
- the hostname and display number on the fly which you may find
- useful:
-HOSTNAME=${DISPLAY%:*}
-FULLDPY=${DISPLAY#*:}
-DPYNUM=${FULLDPY%.*}
-
- A final note may give you some insight into other clever hacks in
- this area: - Check out utaction. It's a very handy little utility
- that can be run as a daemon in the user session which will invoke a
- specified command upon session connects and/or disconnects.
- Personally, I start one up in my .dtprofile as follows:
-utaction -c $HOME/.srconnectrc -d $HOME/.srdisconnectrc &
-
- This then allows me to construct a .srconnectrc script containing
- useful commands I'd like to have run every time I insert my
- smartcard, and a .srdisconnectrc script of commands to be run every
- time I remove my smartcard (or, connect/disconnect to my session
- via NSCM or SC). This can be used for things like notifying a chat
- client of away status, as well as some of the hacks you've
- described on your page such as freeze/unfreeze, or perhaps to
- terminate an xscreensaver and start up a new one with the unix:DPY
- $DISPLAY specification as you describe (although it probably makes
- most sense to do this at login time, as opposed to every connect or
- disconnect event).
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/ssl.html:
-
-
- _________________________________________________________________
-
- Notes on x11vnc SSL Certificates and Key Management:
-
- The simplest scheme ("x11vnc -ssl TMP") is where x11vnc generates a
- temporary, self-signed certificate each time (automatically using
- openssl(1)) and the VNC viewer client accepts the certificate without
- question (e.g. user clicks "Yes" in a dialog box. Perhaps the dialog
- allows them to view the certificate too). Also note stunnel's default
- is to quietly accept all certificates.
-
- The encryption this provides protects against all passive sniffing of
- the VNC traffic and passwords on the network and so it is quite good,
- but it does not prevent a Man-In-The-Middle active attack: e.g. an
- attacker intercepts the VNC client stream and sends it his own Public
- key for SSL negotiation (pretending to be the server). Then it makes a
- connection to SSL x11vnc itself and forwards the data back and forth.
- He can see all the traffic and modify it as well.
-
- Most people don't seem to worry about Man-In-The-Middle attacks these
- days; they are more concerned about passive sniffing of passwords,
- etc. Perhaps someday that will change if attack tools are used more
- widely to perform the attack. NOTE: There are hacker tools like
- dsniff/webmitm and cain that implement SSL Man-In-The-Middle attacks.
- They all rely on the client not bothering to check that the cert is
- valid.
-
- If you are not worried about Man-In-The-Middle attacks you do not have
- to read the techniques described in the rest of this document.
-
- To prevent Man-In-The-Middle attacks, certificates must somehow be
- verified. This requires the VNC client side have some piece of
- information that can be used to verify the SSL x11vnc server.
- Alternatively, although rarely done, x11vnc can verify VNC Clients'
- certificates, see the -sslverify option that is discussed below.
-
- There are a number of ways to have the client authenticate the SSL
- x11vnc server. The quickest way perhaps would be to copy (safely) the
- certificate x11vnc prints out:
-26/03/2006 21:12:00 Creating a temporary, self-signed PEM certificate...
-...
------BEGIN CERTIFICATE-----
-MIIC4TCCAkqgAwIBAgIJAMnwCaOjvEKaMA0GCSqGSIb3DQEBBAUAMIGmMQswCQYD
-VQQGEwJBVTEOMAwGA1UEBxMFTGludXgxITAfBgNVBAsTGGFuZ2VsYS0xMTQzNDI1
-NTIwLjQxMTE2OTEPMA0GA1UEChMGeDExdm5jMS4wLAYDVQQDEyV4MTF2bmMtU0VM
-(more lines) ...
------END CERTIFICATE-----
-
- to the client machine(s) and have the client's SSL machinery (e.g.
- stunnel, Web Browser, or Java plugin) import the certificate. That way
- when the connection to x11vnc is made the client can verify that is it
- the desired server on the other side of the SSL connection.
-
- So, for example suppose the user is using the SSL enabled Java VNC
- Viewer and has incorporated the x11vnc certificate into his Web
- browser on the viewing side. If he gets a dialog that the certificate
- is not verified he knows something is wrong. It may be a
- Man-In-The-Middle attack, but more likely x11vnc certificate has
- changed or expired or his browser was reinstalled and/or lost the
- certificate, etc, etc.
-
- As another example, if the user was using stunnel with his VNC viewer
- (this is mentioned in this FAQ), e.g. STUNNEL.EXE on Windows, then he
- would have to set the "CAfile = path-to-the-cert" and "verify = 2"
- options in the stunnel.conf file before starting up the tunnel. If a
- x11vnc certificate cannot be verified, stunnel will drop the
- connection (and print a failure message in its log file).
-
- A third example, using the VNC viewer on Unix with stunnel the wrapper
- script can be used this way: "ss_vncviewer -verify ./x11vnc.crt
- far-away.east:0" where ./x11vnc.crt is the copied certificate x11vnc
- printed out.
-
- As fourth example, our SSVNC enhanced tightvnc viewer can also use
- these certificate files for server authentication. You can load them
- via the SSVNC 'Certs...' dialog and set 'ServerCert' to the
- certificate file you safely copied there.
-
- Note that in principle the copying of the certificate to the client
- machine(s) itself could be altered by a Man-In-The-Middle attack! You
- can't win; it is very difficult to be completely secure. It is
- unlikely the attacker could predict how you were going to send it
- unless you had, say, done it many times before the same way. SSH is a
- very good way to send it (but of course it too depends on public keys
- being sent unaltered between the two machines!).
-
- If you are really paranoid, I'm sure you'll figure out a really good
- way to transport the certificates. See the Certificate Authority
- scheme below for a way to make this easier (you just have to do it
- once).
-
- _________________________________________________________________
-
- Saving SSL certificates and keys:
-
- Now, it would be very inconvenient to copy the new temporary
- certificate every time x11vnc is run in SSL mode. So for convenience
- there is the "SAVE" keyword to instruct x11vnc to save the certificate
- it creates:
- x11vnc -ssl SAVE -display :0 ...
-
- This behavior is now the default, you must use "TMP" for a temporary
- one. It will save the certificate and private key in these files:
- ~/.vnc/certs/server.crt
- ~/.vnc/certs/server.pem
-
- The ".crt" file contains only the certificate and should be safely
- copied to the VNC Viewer machine(s) that will be authenticating the
- x11vnc server. The ".pem" file contains both the certificate and the
- private key and should be kept secret. (If you don't like the default
- location ~/.vnc/certs, e.g. it is on an NFS share and you are worried
- about local network sniffing, use the -ssldir dir option to point to a
- different directory.)
-
- So the next time you run "x11vnc -ssl SAVE ..." it will read the
- server.pem file directly instead of creating a new one.
-
- You can manage multiple SSL x11vnc server keys in this simple way by
- using:
- x11vnc -ssl SAVE-key2 -display :0 ...
-
- etc, where you put whatever name you choose for the key after "SAVE-".
- E.g. "-ssl SAVE-fred".
-
- Also, if you want to be prompted to possibly change the made up names,
- etc. that x11vnc creates (e.g. "x11vnc-SELF-SIGNED-CERT-7762" for the
- CommonName) for the certificates distinguished name (DN), then use
- "x11vnc -ssl SAVE_PROMPT ...", "x11vnc -ssl SAVE_PROMPT-fred ..." etc.
- when you create the key the first time.
-
- Tip: when prompting, if you choose the CommonName entry to be the full
- internet hostname of the machine the clients will be connecting to
- then that will avoid an annoying dialog box in their Web browsers that
- warn that the CommonName doesn't match the hostname.
-
- _________________________________________________________________
-
- Passphrases for server keys:
-
- Well, since now with the "SAVE" keyword the certificate and key will
- be longer lived, one can next worry about somebody stealing the
- private key and pretending to be the x11vnc server! How to guard
- against this?
-
- The first is that the file is created with perms 600 (i.e. -rw-------)
- to make it harder for an untrusted user to copy the file. A better way
- is to also encrypt the private key with a passphrase. You are prompted
- whether you want to do this or not when the key is first created under
- "-ssl SAVE" mode ("Protect key with a passphrase? y/n"). It is
- suggested that you use a passphrase. The inconvenience is every time
- you run "x11vnc -ssl SAVE ..." you will need to supply the passphrase
- to access the private key:
- 06/04/2006 11:39:11 using PEM /home/runge/.vnc/certs/server.pem 0.000s
-
- A passphrase is needed to unlock an OpenSSL private key (PEM file).
- Enter passphrase>
-
- before x11vnc can continue.
-
- _________________________________________________________________
-
- Being your own Certificate Authority:
-
- A very sophisticated way that scales well if the number of users is
- large is to use a Certificate Authority (CA) whose public certificate
- is available to all of the VNC clients and whose private key has been
- used to digitally sign the x11vnc server certificate(s).
-
- The idea is as follows:
- * A special CA cert and key is generated.
- * Its private key is always protected by a good passphrase since it
- is only used for signing.
- * The CA cert is (safely) distributed to all machines where VNC
- clients will run.
- * One or more x11vnc server certs and keys are generated.
- * The x11vnc server cert is signed with the CA private key.
- * x11vnc is run using the server key. (e.g. "-ssl SAVE")
- * VNC clients (viewers) can now authenticate the x11vnc server
- because they have the CA certificate.
-
- The advantage is the CA cert only needs to be distributed once to the
- various machines, that can be done even before x11vnc server certs are
- generated.
-
- As above, it is important the CA private key and the x11vnc server key
- are kept secret, otherwise someone could steal them and pretend to be
- the CA or the x11vnc server if they copied the key. It is recommended
- that the x11vnc server keys are also protected via a passphrase (see
- the previous section).
-
- Optionally, VNC viewer certs and keys could also be generated to
- enable the x11vnc server to authenticate each client. This is not
- normally done (usually a simple viewer password scheme is used), but
- this can be useful in some situations. These optional steps go like
- this:
- * One or more VNC client certs and keys are generated.
- * These VNC client certs are signed with the CA private key.
- * The VNC client certs+keys are safely distributed to the
- corresponding client machines.
- * x11vnc is told to verify clients by using the CA cert. (e.g.
- "-sslverify CA")
- * When VNC clients (viewers) connect, they must authenticate
- themselves to x11vnc by using their client key.
-
- Again, it is a good idea if the client private keys are protected with
- a passphrase, otherwise if stolen they could be used to gain access to
- the x11vnc server. Once distributed to the client machines, there is
- no need to keep the client key on the CA machine that generated and
- signed it. You can keep the client certs if you like because they are
- public.
-
- _________________________________________________________________
-
- How to do the above CA steps with x11vnc:
-
- Some utility commands are provided to ease the cert+key creation,
- signing, and management: -sslGenCA, -sslGenCert, -sslDelCert,
- -sslEncKey, -sslCertInfo. They basically run the openssl(1) command
- for you to manage the certs/keys. It is required that openssl(1) is
- installed on the machine and available in PATH. All commands can be
- pointed to an alternate toplevel certificate directory via the -ssldir
- option if you don't want to use the default ~/.vnc/certs.
-
- 1) To generate your Certificate Authority (CA) cert and key run this:
- x11vnc -sslGenCA
-
- Follow the prompts, you can modify any informational strings you care
- to. You will also be required to encrypt the CA private key with a
- passphrase. This generates these files:
- ~/.vnc/certs/CA/cacert.pem (the CA public certificate)
- ~/.vnc/certs/CA/private/cakey.pem (the encrypted CA private key)
-
- If you want to use a different directory use -ssldir It must supplied
- with all subsequent SSL utility options to point them to the correct
- directory.
-
- 2) To generate a signed x11vnc server cert and key run this:
- x11vnc -sslGenCert server
-
- As with the CA generation, follow the prompts and you can modify any
- informational strings that you care to. This will create the files:
- ~/.vnc/certs/server.crt (the server public certificate)
- ~/.vnc/certs/server.pem (the server private key + public cert)
-
- It is recommended to protect the server private key with a passphrase
- (you will be prompted whether you want to). You will need to provide
- it whenever you start x11vnc using this key.
-
- 3) Start up x11vnc using this server key:
- x11vnc -ssl SAVE -display :0 ...
-
- (SAVE corresponds to server.pem, see -sslGenCert server somename info
- on creating additional server keys, server-somename.crt ...)
-
- 4) Next, safely copy the CA certificate to the VNC viewer (client)
- machine(s). Perhaps:
- scp ~/.vnc/CA/cacert.pem clientmachine:.
-
- 5) Then the tricky part, make it so the SSL VNC Viewer uses this
- certificate! There are a number of ways this might be done, it depends
- on what your client and/or SSL tunnel is. Some examples:
-
- For the SSL Java VNC viewer supplied with x11vnc in
- classes/ssl/VncViewer.jar or classes/ssl/SignedVncViewer.jar:
- * Import the cacert.pem cert into your Web Browser (e.g. Edit ->
- Preferences -> Privacy & Security -> Manage Certificates ->
- WebSites -> Import)
- * Or Import the cacert.pem cert into your Java Plugin (e.g. run
- ControlPanel, then Security -> Certificates -> Secure Site ->
- Import)
-
- When importing, one would give the browser/java-plugin the path to the
- copied cacert.pem file in some dialog. Note that the Web browser or
- Java plugin is used for the server authentication. If the user gets a
- "Site not verified" message while connecting he should investigate
- further.
-
- For the use of stunnel (e.g. on Windows) one would add this to the
- stunnel.conf:
- # stunnel.conf:
- client = yes
- options = ALL
- CAfile = /path/to/cacert.pem # or maybe C:\path\to\cacert.pem
- [myvncssl]
- accept = 5901
- connect = far-away.east:5900
-
- (then point the VNC viewer to localhost:1).
-
- Here is an example for the Unix stunnel wrapper script ss_vncviewer in
- our SSVNC package:
- ss_vncviewer -verify ./cacert.pem far-away.east:0
-
- Our SSVNC enhanced tightvnc viewer GUI can also use the certificate
- file for server authentication. You can load it via the SSVNC
- 'Certs...' dialog and set 'ServerCert' to the cacert.pem file you
- safely copied there.
-
- _________________________________________________________________
-
- Tricks for server keys:
-
- To create additional x11vnc server keys do something like this:
- x11vnc -sslGenCert server myotherkey
-
- and use it this way:
- x11vnc -ssl SAVE-myotherkey ...
-
- The files will be ~/.vnc/certs/server-myotherkey.{crt,pem}
-
- You can also create a self-signed server key:
- x11vnc -sslGenCert server self:third_key
-
- and use it this way:
- x11vnc -ssl SAVE-self:third_key ...
-
- This key is not signed by your CA. This can be handy to have a key set
- separate from your CA when you do not want to create a 2nd CA
- cert+key.
-
- _________________________________________________________________
-
- Using external CA's:
-
- You don't have to use your own CA cert+key, you can use a third
- party's instead. Perhaps you have a company-wide CA or you can even
- have your x11vnc certificate signed by a professional CA (e.g.
- www.thawte.com or www.verisign.com or perhaps the free certificate
- service www.startcom.org or www.cacert.org).
-
- The advantage to doing this is that the VNC client machines will
- already have the CA certificates installed and you don't have to
- install it on each machine.
-
- To generate an x11vnc server cert+key this way you should generate a
- "request" for a certicate signing something like this (we use the name
- "external" in this example, it could be anything you want):
- x11vnc -sslGenCert server req:external
-
- This will create the request file:
- ~/.vnc/certs/server-req:external.req
-
- Which you should send to the external CA. When you get the signed
- certificate back from them, save it in the file:
- ~/.vnc/certs/server-req:external.crt
-
- and create the .pem this way:
- mv ~/.vnc/certs/server-req:external.key ~/.vnc/certs/server-req:external.
-pem
- chmod 600 ~/.vnc/certs/server-req:external.pem
- cat ~/.vnc/certs/server-req:external.crt >> ~/.vnc/certs/server-req:external.
-pem
-
- You also rename the two files (.crt and .pem) to have a shorter
- basename if you like. E.g.:
- mv ~/.vnc/certs/server-req:external.pem ~/.vnc/certs/server-ext.pem
- mv ~/.vnc/certs/server-req:external.crt ~/.vnc/certs/server-ext.crt
-
- and the use via "x11vnc -ssl SAVE-ext ...", etc.
-
- On the viewer side make sure the external CA's certificate is
- installed an available for the VNC viewer software you plan to use.
-
- _________________________________________________________________
-
- Using Client Keys for Authentication:
-
- You can optionally create certs+keys for your VNC client machines as
- well. After distributing them to the client machines you can have
- x11vnc verify the clients using SSL. Here is how to do this:
-
- x11vnc -sslGenCert client dilbert
- x11vnc -sslGenCert client wally
- x11vnc -sslGenCert client alice
- ...
-
- As usual, follow the prompts if you want to change any of the info
- field values. As always, it is a good idea (although inconvenient) to
- protect the private keys with a passphrase. These files are created:
- ~/.vnc/certs/clients/dilbert.crt
- ~/.vnc/certs/clients/dilbert.pem
- ...
-
- Note that these are kept in a clients subdirectory.
-
- Next, safely copy the .pem files to each corresponding client machine
- and incorporate them into the VNC viewer / SSL software (see the ideas
- mentioned above for the CA and server keys). The only difference is
- these certificates might be referred to as "My Certificates" or
- "Client Certificates". They are used for client authentication (which
- is relatively rare for SSL).
-
- After copying them you can delete the clients/*.pem files for extra
- safety because the private keys are not needed by the x11vnc server.
- You don't really need the clients/*.crt files either (because they
- have been signed by the CA). But they could come in handy for tracking
- or troubleshooting, etc.
-
- Now start up x11vnc and instruct it to verify connecting clients via
- SSL and the CA cert:
- x11vnc -ssl SAVE -sslverify CA
-
- The "CA" special token instructs x11vnc to use its CA signed certs for
- verification.
-
- For arbitrary self-signed client certificates (no CA) it might be
- something like this:
- x11vnc -ssl SAVE -sslverify path/to/client.crt
- x11vnc -ssl SAVE -sslverify path/to/client-hash-dir
- x11vnc -ssl SAVE -sslverify path/to/certs.txt
-
- Where client.crt would be an individual client certificate;
- client-hash-dir a directory of file names based on md5 hashes of the
- certs (see -sslverify); and certs.txt signifies a single file full of
- client certificates.
-
- Finally, connect with your VNC viewer using the key. Here is an
- example for the Unix stunnel wrapper script ss_vncviewer: using client
- authentication (and the standard server authentication with the CA
- cert):
- ss_vncviewer -mycert ./dilbert.pem -verify ./cacert.pem far-away.east:0
-
- Our SSVNC enhanced tightvnc viewer can also use these openssl .pem
- files (you can load them via Certs... -> MyCert dialog).
-
- It is also possible to use -sslverify on a per-client key basis, and
- also using self-signed client keys (x11vnc -sslGenCert client
- self:dilbert)
-
- Now a tricky part is to get Web browsers or Java Runtime to import and
- use the openssl .pem cert+key files. See the next paragraph on how to
- convert them to pkcs12 format. If you find a robust way to import them
- and and get them to use the cert please let us know!
-
- Here is how to convert our openssl crt/pem files to pkcs12 format
- (contains both the client certificate and key) that can be read by Web
- browsers and Java for use in client authentication:
- openssl pkcs12 -export -in mycert.crt -inkey mycert.pem -out mycert.p12
-
- it will ask for a passphrase to protect mycert.p12. Some software
- (e.g. Java ControlPanel) may require a non-empty passphrase. Actually,
- since our .pem contains both the certificate and private key, you
- could just supply it for the -in and remove the -inkey option. It
- appears that for certificates only importing, our .crt file is
- sufficient and can be read by Mozilla/Firefox and Java...
-
- If you have trouble getting your Java Runtime to import and use the
- cert+key, there is a workaround for the SSL-enabled Java applet. On
- the Web browser URL that retrieves the VNC applet, simply add a
- "/?oneTimeKey=..." applet parameter (see ssl-portal for more details
- on applet parameters; you don't need to do the full portal setup
- though). The value of the oneTimeKey will be the very long string that
- is output of the onetimekey program found in the classes/ssl x11vnc
- directory. Or you can set oneTimeKey=PROMPT in which case the applet
- will ask you to paste in the long string. These scheme is pretty ugly,
- but it works. A nice application of it is to make one time keys for
- users that have already logged into a secure HTTPS site via password.
- A cgi program then makes a one time key for the logged in user to use:
- it is passed back over HTTPS as the applet parameter in the URL and so
- cannot be sniffed. x11vnc is run to use that key via -sslverify.
-
- Update: as of Apr 2007 in the 0.9.1 x11vnc tarball there is a new
- option setting "-users sslpeer=" that will do a switch user much like
- -unixpw does, but this time using the emailAddress field of the
- Certificate subject of the verified Client. This mode requires
- -sslverify turned on to verify the clients via SSL. This mode can be
- useful in situations using -create or -svc where a new X server needs
- to be started up as the authenticated user (but unlike in -unixpw
- mode, the unix username is not obviously known).
-
- _________________________________________________________________
-
- Revoking Certificates:
-
- A large, scaled-up installation may benefit from being able to revoke
- certificates (e.g. suppose a user's laptop with a vnc client or server
- key is compromised.) You can use this option with x11vnc: -sslCRL. See
- the info at that link for a guide on what openssl(1) commands you will
- need to run to revoke a certificate.
-
- _________________________________________________________________
-
- Additional utlities:
-
- You can get information about your keys via -sslCertInfo. These lists
- all your keys:
- x11vnc -sslCertInfo list
- x11vnc -sslCertInfo ll
-
- (the latter is long format).
-
- These print long output, including the public certificate, for
- individual keys:
- x11vnc -sslCertInfo server
- x11vnc -sslCertInfo dilbert
- x11vnc -sslCertInfo all (every key, very long)
-
- If you want to add a protecting passphrase to a key originally created
- without one:
- x11vnc -sslEncKey SAVE
- x11vnc -sslEncKey SAVE-fred
-
- To delete a cert+key:
- x11vnc -sslDelCert SAVE
- x11vnc -sslDelCert SAVE-fred
- x11vnc -sslDelCert wally
-
- (but rm(1) will be just as effective).
-
- _________________________________________________________________
-
- Chained Certificates:
-
- There is increasing interest in using chained CA's instead of a single
- CA. The merits of using chained CA's are not described here besides to
- say its use may make some things easier when a certificate needs to be
- revoked.
-
- x11vnc supports chained CA certificates. We describe a basic use case
- here.
-
- Background: Of course the most straight forward way to use SSL with
- x11vnc is to use no CA at all (see above): a self-signed certificate
- and key is used and its certificate needs to be safely copied to the
- client side. This is basically the same as the SSH style of managing
- keys. Next level up, one can use a single CA to sign server keys: then
- only the CA's certificate needs to be safely copied to the client
- side, this can happen even before any server certs are created (again,
- see all of the discussion above.)
-
- With a certificate chain there are two or more CA's involved. Perhaps
- it looks like this:
- root_CA ---> intermediate_CA ---> server_cert
-
- Where the arrow basically means "signs".
-
- In this usage mode the client (viewer-side) will have root_CA's
- certificate available for verifying (and nothing else.) If the viewer
- only received server_cert's certificate, it would not have enough info
- to verify the server. The client needs to have intermediate_CA's cert
- as well. The way to do this with x11vnc (i.e. an OpenSSL using app) is
- to concatenate the server_cert's pem and the intermediate_CA's
- certificate together.
-
- For example, suppose the file intermediate_CA.crt had
- intermediate_CA's certificate. And suppose the file server_cert.pem
- had the server's certificate and private key pair as described above
- on this page. We need to do this:
- cat intermediate_CA.crt >> server_cert.pem
-
- (Note: the order of the items inside the file matters; intermediate_CA
- must be after the server key and cert) and then we run x11vnc like
- this:
- x11vnc -ssl ./server_cert.pem ...
-
- Then, on the VNC viewer client side, the viewer authenticates the
- x11vnc server by using root_CA's certificate. Suppose that is in a
- file named root_CA.crt, then using the SSVNC wrapper script
- ss_vncviewer (which is also included in the SSVNC package) as our
- example, we have:
- ss_vncviewer -verify ./root_CA.crt hostname:0
-
- (where "hostname" is the machine where x11vnc is running.) One could
- also use the SSVNC GUI setting Certs -> ServerCert to the root_CA.crt
- file. Any other SSL enabled VNC viewer would use root_CA.crt in a
- similar way.
- _________________________________________________________________
-
- Creating Chained Certificates:
-
- Here is a fun example using VeriSign's "Trial Certificate" program.
- Note that VeriSign has a Root CA and also an Intermediate CA and uses
- the latter to sign customers certificates. So this provides an easy
- way to test out the chained certificates mechanism with x11vnc.
-
- First we created a test x11vnc server key:
- openssl genrsa -out V1.key 1024
-
- then we created a certificate signing request (CSR) for it:
- openssl req -new -key V1.key -out V1.csr
-
- (we followed the prompts and supplied information for the various
- fields.)
-
- Then we went to VeriSign's page http://www.verisign.com/ssl/index.html
- and clicked on "FREE TRIAL" (the certificate is good for 14 days.) We
- filled in the forms and got to the point where it asked for the CSR
- and so we pasted in the contents of the above V1.csr file. Then, after
- a few more steps, VeriSign signed and emailed us our certificate.
-
- The VeriSign Trial certificates were found here:
- http://www.verisign.com/support/verisign-intermediate-ca/Trial_Secure_Server_
-Root/index.html
- http://www.verisign.com/support/verisign-intermediate-ca/trial-secure-server-
-intermediate/index.html
-
- The former was pasted into a file V-Root.crt and the latter was pasted
- into V-Intermediate.crt
-
- We pasted our Trial certificate that VeriSign signed and emailed to us
- into a file named V1.crt and then we typed:
- cat V1.key V1.crt > V1.pem
- cat V1.pem V-Intermediate.crt > V1-combined.pem
- chmod 600 V1.pem V1-combined.pem
-
- So now the file V1-combined.pem has our private key and (VeriSign
- signed) certificate and VeriSign's Trial Intermediate certificate.
-
- Next, we start x11vnc:
- x11vnc -ssl ./V1-combined.pem ...
-
- and finally, on the viewer side (SSVNC wrapper script example):
- ss_vncviewer -verify ./V-Root.crt hostname:0
-
- One will find that only that combination of certs and keys will work,
- i.e. allow the SSL connection to be established. Every other
- combination we tried failed (note that ss_vncviewer uses the external
- stunnel command to handle the SSL so we are really testing stunnel's
- SSL implementation on the viewer side); and so the system works as
- expected.
- _________________________________________________________________
-
- VNC Client Authentication using Certificate Chains:
-
- Now, going the other way around with the client authenticating himself
- via this chain of SSL certificates, x11vnc is run this way:
- x11vnc -ssl SAVE -sslverify ./V-Root.crt ...
-
- (note since the server must always supply a cert, we use its normal
- self-signed, etc., one via "-ssl SAVE" and use the VeriSign root cert
- for client authentication via -sslverify. The viewer must now supply
- the combined certificates, e.g.:
- ss_vncviewer -mycert ./V1-combined.pem hostname:0
- _________________________________________________________________
-
- Using OpenSSL and x11vnc to create Certificate Chains:
-
- Although the x11vnc CA mechanism (-sslGenCA and -sslGenCert; see
- above) was designed to only handle a single root CA (to sign server
- and/or client certs) it can be coerced into creating a certificate
- chain by way of an extra openssl(1) command.
-
- We will first create two CA's via -sslGenCA; then use one of these CA
- to sign the other; create a new (non-CA) server cert; and append the
- intermediate CA's cert to the server cert to have everything needed in
- the one file.
-
- Here are the commands we ran to do what the previous paragraph
- outlines.
-
- First we create the two CA's, called CA_root and CA_Intermediate here,
- in separate directories via x11vnc:
- x11vnc -ssldir ~/CA_Root -sslGenCA
- (follow the prompts, we included "CA_Root", e.g. Common Name, to aid ident
-ifying it)
-
- x11vnc -ssldir ~/CA_Intermediate -sslGenCA
- (follow the prompts, we included "CA_Intermediate", e.g. Common Name, to a
-id identifying it)
-
- Next backup CA_Intermediate's cert and then sign it with CA_Root:
- mv ~/CA_Intermediate/CA/cacert.pem ~/CA_Intermediate/CA/cacert.pem.ORIG
- cd ~/CA_Root
- openssl ca -config ./CA/ssl.cnf -policy policy_anything -extensions v3_ca -no
-text -ss_cert ~/CA_Intermediate/CA/cacert.pem.ORIG -out ~/CA_Intermediate/CA/ca
-cert.pem
-
- Note that it is required to cd to the ~/CA_Root directory and run the
- openssl command from there.
-
- You can print out info about the cert you just modified by:
- openssl x509 -noout -text -in ~/CA_Intermediate/CA/cacert.pem
-
- Now we create an x11vnc server cert named "test_chain" that is signed
- by CA_Intermediate:
- x11vnc -ssldir ~/CA_Intermediate -sslGenCert server test_chain
- (follow the prompts)
-
- You can print out information about this server cert just created via
- this command:
- x11vnc -ssldir ~/CA_Intermediate -sslCertInfo SAVE-test_chain
-
- This will tell you the full path to the server certificate, which is
- needed because we need to manually append the CA_Intermediate cert for
- the chain to work:
- cat ~/CA_Intermediate/CA/cacert.pem >> ~/CA_Intermediate/server-test_chain.pe
-m
-
- Now we are finally ready to use it. We can run x11vnc using this
- server cert+key by either this command:
- x11vnc -ssldir ~/CA_Intermediate -ssl SAVE-test_chain ...
-
- or this command:
- x11vnc -ssl ~/CA_Intermediate/server-test_chain.pem ...
-
- since they are equivalent (both load the same pem file.)
-
- Finally we connect via VNC viewer that uses CA_Root to verify the
- server. As before we use ss_vncviewer:
- ss_vncviewer -verify ~/CA_Root/CA/cacert.pem hostname:0
-
- Client Certificates (see above) work in a similar manner.
-
- So although it is a little awkward with the extra steps (e.g.
- appending the CA_Intermediate cert) it is possible. If you want to do
- this entirely with openssl(1) you will have to learn the openssl
- commands corresponding to -genCA and -genCert. You may be able to find
- guides on the Internet to do this. Starting with x11vnc 0.9.10, you
- can have it print out the wrapper scripts it uses via: -sslScripts
- (you will still need to fill in a few pieces of information; ask if it
- is not clear from the source code.)
-
- _________________________________________________________________
-
- More info:
-
- See also this article for some some general info and examples using
- stunnel and openssl on Windows with VNC. Also
- http://www.stunnel.org/faq/certs.html is a very good source of
- information on SSL certificate creation and management.
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/ssl-portal.html:
-
-
- _________________________________________________________________
-
- Using Apache as an SSL Gateway to multiple x11vnc servers inside a
- firewall:
-
- Background:
-
- The typical way to allow access to x11vnc (or any other VNC server)
- running on multiple workstations inside a firewall is via SSH. The
- user somewhere out on the Internet logs in to the SSH gateway machine
- and uses port forwarding (e.g. ssh -t -L 5900:myworkstation:5900
- user@gateway) to set up the encrypted channel that VNC is then
- tunneled through. Next he starts up the VNC viewer on the machine
- where he is sitting directed to the local tunnel port (e.g.
- localhost:0).
-
- The SSH scheme is nice because it is a widely used and well tested
- login technique for users connecting to machines inside their company
- or home firewall. For VNC access it is a bit awkward, however, because
- SSH needs to be installed on the Viewer machine and the user usually
- has to rig up his own port redirection plumbing (however, see our
- other tool).
-
- Also, some users have restrictive work environments where SSH and
- similar applications are prohibited (i.e. only outgoing connections to
- standard WWW ports from a browser are allowed, perhaps mediated by a
- proxy server). These users have successfully used the method described
- here for remote access.
-
- With the SSL support in x11vnc and the SSL enabled Java VNC viewer
- applet, a convenient and secure alternative exists that uses the
- Apache webserver as a gateway. The idea is that the company or home
- internet connection is already running apache as a web server (either
- SSL or non-SSL) and we add to it the ability to act as a gateway for
- SSL VNC connections. The only thing needed on the Viewer side is a
- Java enabled Web Browser: the user simply enters a URL that starts the
- entire VNC connection process. No VNC or SSH specific software needs
- to be installed on the viewer side machine.
-
- The stunnel VNC viewer stunnel wrapper script provided (ss_vncviewer)
- can also take advantage of the method described here with its -proxy
- option.
-
- _________________________________________________________________
-
- Simpler Solutions: This apache SSL VNC portal solution may be too much
- for you. It is mainly intended for automatically redirecting to
- MULTIPLE workstations inside the firewall. If you only have one or two
- inside machines that you want to access, the method described here is
- overly complicated! See below for some simpler (and still non-SSH)
- encrypted setups.
-
- Also see the recent (Mar/2010) desktop.cgi x11vnc desktop web login
- CGI script that achieves much of what the method describes here
- (especially if its 'port redirection' feature is enabled.)
- _________________________________________________________________
-
-
-
- There are numerous ways to achieve this with Apache. We present one of
- the simplest ones here.
-
- Important: these sorts of schemes allow incoming connections from
- anywhere on the Internet to fixed ports on machines inside the
- firewall. Care must be taken to implement and test thoroughly. If one
- is paranoid one can (and should) add extra layers of protection. (e.g.
- extra passwords, packet filtering, SSL certificate verification, etc).
-
- Also, it is easy to miss the point that unless precautions are taken
- to verify SSL Certificates, then the VNC Viewer is vulnerable to
- man-in-the-middle attacks (but not to the more common passive sniffing
- attacks). Note that there are hacker tools like dsniff/webmitm and
- cain that implement SSL Man-In-The-Middle attacks. They rely on the
- client not bothering to check the cert.
- _________________________________________________________________
-
- The Holy Grail: a single https port (443)
-
- Before we discuss the self-contained apache examples here, we want to
- mention that many x11vnc users who read this page and implement the
- apache SSL VNC portal ask for something that (so far) seems difficult
- or impossible to do entirely inside apache:
- * A single port, 443 (the default https:// port), is open to the
- Internet
- * It is HTTPS/SSL encrypted
- * It handles both VNC traffic and Java VNC Applet downloads.
- * And the server can also serve normal HTTPS webpages, CGI, etc.
-
- It is the last item that makes it tricky (otherwise the method
- described on this page will work). If you are interested in such a
- solution and are willing to run a separate helper program
- (connect_switch) look here. Also, see this apache patch.
- _________________________________________________________________
-
- Example:
-
- The scheme described here sets up apache on the firewall/gateway as a
- regular Web proxy into the intranet and allows connections to a single
- fixed port on a limited set of machines.
-
- The configuration described in this section does not use the mod_ssl
- apache module (the optional configuration described in the section
- "Downloading the Java applet to the browser via HTTPS" does take
- advantage of mod_ssl)
-
- In this example suppose the gateway machine running apache is named
- "www.gateway.east" (e.g. it may also provide normal web service). We
- also choose the Internet-facing port for this VNC service to be port
- 563. One could choose any port, including the default HTTP port 80.
-
- Detail: We choose 563 because it is the rarely used SNEWS port that is
- often allowed by Web proxies for the CONNECT method. The idea is the
- user may be coming out of another firewall using a proxy (not the one
- we describe here, that is, the case when two proxies are involved,
- e.g. one at work and another Apache (described here) at home
- redirecting into our firewall; the "double proxy" or "double firewall"
- problem). Using port 563 simplifies things because CONNECT's to it are
- usually allowed by default.
-
- We also assume all of the x11vnc servers on the internal machines are
- all listening on port 5915 ("-rfbport 5915") instead of the default
- 5900. This is to limit any unintended proxy redirections to a lesser
- used port, and also to stay out of the way of normal VNC servers on
- the same machines. One could obviously implement a scheme that handles
- different ports, but we just discuss this simple setup here.
-
- So we basically assume x11vnc has been started this way on all of the
- workstations to be granted VNC access:
- x11vnc -ssl SAVE -http -display :0 -forever -rfbauth ~/.vnc/passwd -rfbport 5
-915
-
- i.e. we force SSL VNC connections, port 5915, serve the Java VNC
- viewer applet, and require a VNC password (another option would be
- -unixpw). The above command could also be run out of inetd(8). It can
- also be used to autodetect the user's display and Xauthority data.
-
-
- These sections are added to the httpd.conf apache configuration file
- on www.gateway.east:
-
-# In the global section you need to enable these modules.
-# Note that the ORDER MATTERS! mod_rewrite must be before mod_proxy
-# (so that we can check the allowed host list via rewrite)
-#
-LoadModule rewrite_module modules/mod_rewrite.so
-LoadModule proxy_module modules/mod_proxy.so
-LoadModule proxy_connect_module modules/mod_proxy_connect.so
-LoadModule proxy_ftp_module modules/mod_proxy_ftp.so
-LoadModule proxy_http_module modules/mod_proxy_http.so
-<IfDefine SSL>
-LoadModule ssl_module modules/mod_ssl.so
-</IfDefine>
-
-
-# Near the bottom of httpd.conf you put the port 563 virtual host:
-
-Listen 563
-
-<VirtualHost *:563>
-
- # Allow proxy CONNECT requests *only* to port 5915.
- # If the machines use different ports, e.g. 5916 list them here as well:
- #
- ProxyRequests On
- AllowCONNECT 5915
-
- RewriteEngine On
-
- # Convenience rules to expand applet parameters. These do not have a traili
-ng "/"
- #
- # /vnc for http jar file downloading:
- #
- RewriteRule /vnc/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1 [R,NE,L]
- RewriteRule /vnc/trust/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&trustAllVncCerts=yes [R,NE,L]
- RewriteRule /vnc/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes [R,NE,L]
- RewriteRule /vnc/trust/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes&trustAllVncCerts=yes [R,NE,L]
-
- # Read in the allowed host to vnc display mapping file. It looks like:
- #
- # host1 15
- # host2 15
- # ...
- #
- # the display "15" means 5815 for http applet download, 5915 for SSL vnc.
- #
- RewriteMap vnchosts txt:/dist/apache/conf/vnc.hosts
-
- # Proxy: check for the CONNECT hostname and port being in the vnc.hosts list
-.
- #
- RewriteCond %{THE_REQUEST} ^CONNECT [NC]
- RewriteCond %{REQUEST_URI} ^(.*):(.*)$
- RewriteCond ${vnchosts:%1|NOTFOUND} NOTFOUND
- RewriteRule ^.*$ /VNCFAIL [F,L]
-
- RewriteCond %{THE_REQUEST} ^CONNECT [NC]
- RewriteCond %{REQUEST_URI} ^(.*):(.*)$
- RewriteCond 59${vnchosts:%1}=%2 !^(.*)=(\1)$
- RewriteRule ^.*$ /VNCFAIL [F,L]
-
-
- # Remap /vnc to the proxy http download (e.g. http://host:5815)
- #
- # First, fail if it starts with the string /vnc0:
- #
- RewriteRule ^/vnc0.* /VNCFAIL [F,L]
- #
- # Next, map the prefix to /vnc0/host:protocol:port
- #
- RewriteRule ^/vnc/([^/]+)/(.*) /vnc0/$1:http:58${vnchosts:$1|NOTFOUND}/$2
-[NE]
- #
- # Drop any not found:
- #
- RewriteRule ^/vnc0.*NOTFOUND.* /VNCFAIL [F,L]
-
- # Construct the proxy URL and retrieve it:
- #
- RewriteRule ^/vnc0/([^/]+):([^/]+):([^/]+)/(.*) $2://$1:$3/$4 [P,NE,L]
-
-</VirtualHost>
-
- Then restart apache (perhaps: "apachectl stop; apachectl start").
-
- Note that the listing of allowed internal workstations is done in an
- external file (/dist/apache/conf/vnc.hosts in the example above), the
- format is like this:
-# allowed vnc hosts file:
-hostname1 15
-hostname2 15
-...
-
- You list the hostname and the VNC display (always 15 in our example).
- Only to these hosts will the external VNC viewers be able to connect
- to (via the HTTP CONNECT method).
-
- The above setup requires mod_rewrite and mod_proxy be enabled in the
- apache web server. In this example they are loaded as modules (and
- note that mod_rewrite must be listed before mod_proxy);
-
- The user at the Java enabled Web browser would simply enter this URL
- into the browser:
- http://www.gateway.east:563/vnc/host2
-
- to connect to internal workstation host2, etc.
-
- Important: do not put a trailing "/" on the URL, since that will
- defeat the RewriteRules that look for the hostname at the very end.
-
- There will be a number of SSL certificate, etc, dialogs he will have
- to respond to in addition to any passwords he is required to provide
- (this depends on how you set up user authentication for x11vnc).
-
- If a second Web proxy is involved (i.e. the user's browser is inside
- another firewall and policy requires using a Web proxy server) then
- use this URL:
- http://www.gateway.east:563/vnc/proxy/host2
-
- This will involve downloading a signed java viewer applet jar file
- that is able to interact with the internal proxy for the VNC
- connection. See this FAQ for more info on how this works. Note:
- sometimes with the Proxy case if you see 'Bad Gateway' error you will
- have to wait 10 or so seconds and then hit reload. This seems to be
- due to having to wait for a Connection Keepalive to terminate...
-
- For completeness, the "trust" cases that skip a VNC certificate dialog
- (discussed below) would be entered as:
- http://www.gateway.east:563/vnc/trust/host2
- http://www.gateway.east:563/vnc/trust/proxy/host2
-
- You can of course choose shorter or more easy to remember URL formats.
- Just change the Convenience RewriteRules in httpd.conf.
-
- _________________________________________________________________
-
- Port Variations:
-
- Note that you can run this on the default HTTP port 80 instead of port
- 563. If you do not expect to have a browser connecting from inside a
- proxying firewall (where sometimes only connections to ports 443 and
- 563 are allowed) this should be fine. Use "80" instead of "563" in the
- httpd.conf config file (you may need to merge it with other default
- port 80 things you have there).
-
- Then the URL's will be a bit simpler:
- http://www.gateway.east/vnc/host2
- http://www.gateway.east/vnc/trust/host2
-
- etc.
-
- Besides 80 one could use any other random port number (since there are
- so many port scans on 80, a little obscurity might be useful).
-
- One option is to use port "443" (the default https:// port) instead of
- "563". In this case Apache is not configured for mod_ssl; we just
- happen to use port "443" in the way any random port would be used.
- This could be handy if the Viewer side environment is restrictive in
- that it only allows outgoing connections to ports 80 and 443 (and,
- say, you didn't want to use port 80, or you wanted to use 80 for
- something else). Another reason for using 443 would be some web proxy
- environments only allow the CONNECT method to go to port 443 (and not
- even the case 563 we use above).
-
- _________________________________________________________________
-
- Details:
-
- Let's go through the httpd.conf additions in detail from the top.
-
- The LoadModules directives load the necessary apache modules. Note
- that mod_rewrite must be listed first. If you are compiling from
- scratch something like this worked for us:
- ./configure --enable-proxy=shared --enable-proxy-connect=shared --enable-ssl=
-shared --enable-rewrite=shared --prefix=/dist/apache
-
- Then the VirtualHost *:563 virtual host section starts.
-
- The "ProxyRequests On" and "AllowCONNECT 5915" enable the web server
- to forward proxy requests to port 5915 (and only this port) INSIDE the
- firewall. Think about the implications of this thoroughly and test it
- carefully.
-
- The RewriteRule's are for convenience only so that the URL entered
- into the Web browser does not need the various extra parameters, e.g.:
- http://www.gateway.east:563/vnc/host2/index.vnc?CONNECT=host2+5915&PORT=563,
-blah,blah...
-
- (or otherwise make direct edits to index.vnc to set these parameters).
- The forceProxy=yes parameter is passed to the applet to force the use
- of a outgoing proxy socket connection. Use it only if the Web browser
- is inside a separate Web proxying environment (i.e. large corporation)
-
- The rewrites with parameter urlPrefix are described under Tricks for
- Better Response. The "trust" ones (also described under Tricks) with
- trustAllVncCerts tell the Java VNC applet to skip a dialog asking
- about the VNC Certificate. They are a bit faster and more reliable
- than the original method. In the best situation they lead to being
- logged in 20 seconds or less (without them the time to login can be
- much longer since a number of connections must timeout).
-
- All of the x11vnc Java Viewer applet parameters are described in the
- file classes/ssl/README
-
- The external file /dist/apache/conf/vnc.hosts containing the allowed
- VNC server hostnames is read in. Its 2nd column contains the VNC
- display of the host (always 15 in our example; if you make it vary you
- will need to adjust some lines in the httpd.conf accordingly, e.g.
- AllowCONNECT). This list is used to constrain both the Jar file
- download URL and the proxy CONNECT the VNC viewer makes to only the
- intended VNC servers.
-
- Limiting the proxy CONNECT is done with the two sets of RewriteCond
- conditions.
-
- Limiting the Jar file download URL is done in the remaining 4
- RewriteRule's.
-
- Note that these index.vnc and VncViewer.jar downloads to the browser
- are not encrypted via SSL, and so in principle could be tampered with
- by a really bad guy. The subsequent VNC connection, however, is
- encrypted through a single SSL connection (it makes a CONNECT straight
- to x11vnc). See below for how to have these initial downloads
- encrypted as well (if the apache web server has SSL/mod_ssl, i.e.
- https, enabled and configured).
-
- Unfortunately the Java VNC viewer applet currently is not able to save
- its own list of Certificates (e.g. the user says trust this VNC
- certificate 'always'). This is because an applet it cannot open local
- files, etc. Sadly, the applet cannot even remember certificates in the
- same browser session because it is completely reinitialized for each
- connection (see below).
-
- _________________________________________________________________
-
- Too Much?
-
- If these apache rules are a little too much for you, there is a little
- bit simpler scheme where you have to list each of the individual
- machines in the httpd.conf and ssl.conf files. It may be a little more
- typing to maintain, but perhaps being more straight forward (less
- RewriteRule's) is desirable.
-
- _________________________________________________________________
-
- Problems?
-
- To see example x11vnc output for a successful https://host:5900/
- connection with the Java Applet see This Page.
-
- _________________________________________________________________
-
- Some Ideas for adding extra authentication, etc. for the paranoid:
- * VNC passwords: -rfbauth, -passwdfile, or -usepw. Even adding a
- simple company-wide VNC password helps block unwanted access.
- * Unix passwords: -unixpw
- * SSL Client certificates: -sslverify
- * Apache AuthUserFile directive: .htaccess, etc.
- * Filter connections based on IP address or hostname.
- * Use Port-knocking on your firewall as described in: Enhanced
- TightVNC Viewer (ssvnc).
- * Add proxy password authentication (requires Viewer changes?)
- * Run a separate instance of Apache that provides this VNC service
- so it can be brought up and down independently of the normal web
- server.
- * How secure is the Client side? Public machines in internet cafes,
- etc, are often hacked, with backdoors and VNC servers of their
- own. Prefer using your own firewalled laptop to a public machine.
-
-
- _________________________________________________________________
-
- Using non-Java viewers with this scheme:
-
- The ss_vncviewer stunnel wrapper script for VNC viewers has the -proxy
- option that can take advantage of this method.
- ss_vncviewer -proxy www.gateway.east:563 host1:15
-
- For the case of the "double proxy" situation (see below) supply both
- separated by a comma.
- ss_vncviewer -proxy proxy1.foobar.com:8080,www.gateway.east:563 host1:15
-
- For the Enhanced TightVNC Viewer (ssvnc) GUI (it uses ss_vncviewer on
- Unix) put 'host1:15' into the 'VNC Server' entry box, and here are
- possible Proxy/Gateway entries
- Proxy/Gateway: www.gateway.east:563
- Proxy/Gateway: proxy1.foobar.com:8080,www.gateway.east:563
-
- then click on the 'Connect' button.
-
- _________________________________________________________________
-
- Downloading the Java applet to the browser via HTTPS:
-
- To have the Java applet downloaded to the user's Web Browser via an
- encrypted (and evidently safer) SSL connection the Apache webserver
- should be configured for SSL via mod_ssl.
-
- It is actually possible to use the x11vnc Key Management utility
- "-sslGenCert" to generate your Apache/SSL .crt and .key files. (In
- brief, run something like "x11vnc -sslGenCert server self:apache" then
- copy the resulting self:apache.crt file to conf/ssl.crt/server.crt and
- extract the private key part from self:apache.pem and paste it into
- conf/ssl.key/server.key). Setting the env var REQ_ARGS='-days 1095'
- before running x11vnc will bump up the expiration date (3 years in
- this case).
-
- Or you can use the standard methods described in the Apache mod_ssl
- documentation to create your keys. Then restart Apache, usually
- something like "apachectl stop" followed by "apachectl startssl"
-
- In addition to the above sections in httpd.conf one should add the
- following to ssl.conf:
- SSLProxyEngine On
-
- RewriteEngine On
-
- # Convenience rules to expand applet parameters. These do not have a traili
-ng "/"
- #
- # /vnc http jar file downloading:
- #
- RewriteRule /vnc/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vnc_2F_$1 [R,NE,L]
- RewriteRule /vnc/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes [R,N
-E,L]
- #
- # (we skipped the "trust" ones above, put them in if you like)
- #
- # /vncs https jar file downloading:
- #
- RewriteRule /vncs/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1 [R,NE,L]
- RewriteRule /vncs/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes [R,
-NE,l]
- RewriteRule /vncs/trust/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&trustAllVncCerts=y
-es [R,NE,L]
- RewriteRule /vncs/trust/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$
-1+5915&PORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes&tru
-stAllVncCerts=yes [R,NE,L]
-
- # Convenience rules used for the connect_switch helper (requires Listen 127.
-0.0.1:443 above):
- #
- RewriteRule /vnc443/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$
-1+5915&PORT=443&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1 [R,NE,L]
- RewriteRule /vnc443/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$
-1+5915&PORT=443&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes [R,
-NE,L]
- RewriteRule /vnc443/trust/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$
-1+5915&PORT=443&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&trustAllVncCerts=y
-es [R,NE,L]
- RewriteRule /vnc443/trust/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$
-1+5915&PORT=443&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes&tru
-stAllVncCerts=yes [R,NE,L]
-
- # Read in the allowed host to vnc display mapping file. It looks like:
- #
- # host1 15
- # host2 15
- # ...
- #
- # the display "15" means 5915 for SSL VNC and 5815 for http applet download.
- #
- RewriteMap vnchosts txt:/dist/apache/conf/vnc.hosts
-
-
- # Remap /vnc and /vncs to the proxy http download (e.g. https://host:5915)
- #
- # First, fail if it starts with the string /vnc0:
- #
- RewriteRule ^/vnc0.* /VNCFAIL [F,L]
- #
- # Next, map the prefix to /vnc0:host:protocol:port
- #
- RewriteRule ^/vnc/([^/]+)/(.*) /vnc0/$1:http:58${vnchosts:$1|NOTFOUND}/$2
-[NE]
- RewriteRule ^/vncs/([^/]+)/(.*) /vnc0/$1:https:59${vnchosts:$1|NOTFOUND}/$2
-[NE]
- #
- # Drop any not found:
- #
- RewriteRule ^/vnc0.*NOTFOUND.* /VNCFAIL [F,L]
-
- # Construct the proxy URL and retrieve it:
- #
- RewriteRule ^/vnc0/([^/]+):([^/]+):([^/]+)/(.*) $2://$1:$3/$4 [P,NE,L]
-
- This is all in the "<VirtualHost _default_:443>" section of ssl.conf.
-
- The user could then point the Web Browser to:
- https://www.gateway.east/vnc/host2
-
- or
- https://www.gateway.east/vnc/proxy/host2
-
- for the "double proxy" case. (Important: do not put a trailing "/" on
- the URL, since that will defeat the RewriteRules.)
-
- As with the httpd.conf case, the external file
- (/dist/apache/conf/vnc.hosts in the above example) contains the
- hostnames of the allowed VNC servers.
-
- Note that inside the firewall the Java applet download traffic is not
- encrypted (only over the Internet is SSL used) for these cases:
- https://www.gateway.east/vnc/host2
- https://www.gateway.east/vnc/proxy/host2
-
- However for the special "vncs" rules above:
- https://www.gateway.east/vncs/host2
-
- the Java applet download is encrypted via SSL for both legs. Note that
- the two legs are two separate SSL sessions. So the data is decrypted
- inside an apache process and reencrypted by the apache process for the
- 2nd SSL session inside the same apache process (a very small gap one
- might overlook).
-
- The "vncs/trust" ones are like the "trust" ones described earlier
- https://www.gateway.east/vncs/trust/mach2
-
- and similarly for the httpsPort ones. See Tricks for Better Response.
-
- In all of the above cases the VNC traffic from Viewer to x11vnc is
- encrypted end-to-end in a single SSL session, even for the "double
- proxy" case because the CONNECT method is used (there are actually two
- CONNECT's for the "double proxy" case). This part (the VNC traffic) is
- the most important part to have encrypted.
-
- Note that the Certificate dialogs the user has in his web browser will
- be for the Apache Certificate, while for the Java applet it will be
- the x11vnc certificate.
-
- Note also that you can have Apache serve up the Jar file VncViewer.jar
- and/or index.vnc/proxy.vnc instead of each x11vnc if you want to.
-
- The rules in ssl.conf are similar to the ones in httpd.conf and so are
- not discussed in detail. The only really new thing is the /vncs
- handling to download the applet jar via HTTPS on port 5915.
-
- The special entries "/vnc443" are only used for the special helper
- program (connect_switch) for the https port 443 only mode discussed
- here.
-
- _________________________________________________________________
-
- INETD automation:
-
- The "single-port" (i.e. 5915) HTTPS applet download and VNC connection
- aspect shown here is convenient and also enables having x11vnc run out
- of inetd. That way x11vnc is run on demand instead of being run all
- the time (the user does not have to remember to start it). The first
- connections to inetd download index.vnc and the Jar file (via https)
- and the the last connection to inetd establishes the SSL VNC
- connection. Since x11vnc is restarted for each connection, this will
- be a bit slower than the normal process.
-
- For example, the /etc/inetd.conf line could be:
- 5915 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc_ssl.sh
-
- where the script x11vnc_ssl.sh looks something like this:
-#!/bin/sh
-
-/usr/local/bin/x11vnc -inetd -oa /var/log/x11vnc-15.log \
- -ssl SAVE -http -unixpw -localhost \
- -display :0 -auth /home/THE_USER/.Xauthority
-
- where, as usual, the inetd launching needs to know which user is
- typically using the display on that machine. One could imagine giving
- different users different ports, 5915, 5916, etc. to distinguish (then
- the script would need to be passed the username). mod_rewrite could be
- used to automatically map username in the URL to his port number.
-
- A better way is to use the "-display WAIT:cmd=FINDDISPLAY" feature to
- autodetect the user and Xauthority data:
-#!/bin/sh
-
-/usr/local/bin/x11vnc -inetd -oa /var/log/x11vnc-15.log \
- -ssl SAVE -http -unixpw -localhost -users unixpw= \
- -find
-
- (we have used the alias -find for "-display WAIT:cmd=FINDDISPLAY".)
- This way the user must supply his Unix username and password and then
- his display and Xauthority data on that machine will be located and
- returned to x11vnc to allow it to attach. If he doesn't have a display
- running on that machine or he fails to log in correctly, the
- connection will be dropped.
-
- The variant "-display WAIT:cmd=FINDCREATEDISPLAY" (aliased by
- "-create") will actually create a (virtual or real) X server session
- for the user if one doesn't already exist. See here for details.
-
- To enable inetd operation for the non-HTTPS Java viewer download (port
- 5815 in the above httpd.conf example) you will need to run x11vnc in
- HTTPONCE mode on port 5815: For example, the /etc/inetd.conf line
- could be:
- 5815 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc \
- -inetd -prog /usr/local/bin/x11vnc -oa /var/log/x11vnc-15.log \
- -http_ssl -display WAIT:cmd=HTTPONCE
-
- where the long inetd.conf line has been split. Note how the -http_ssl
- tries to automatically find the .../classes/ssl subdirectory. This
- requires the -prog option available in x11vnc 0.8.4 (a shell script
- wrapper, e.g. /usr/local/bin/x11vnc_http.sh can be used to work around
- this).
-
- Also note the use of "-ssl SAVE" above. This way a saved server.pem is
- used for each inetd invocation (rather generating a new one each time
- as happens for "-ssl TMP"). Note that it cannot have a protecting
- passphrase because inetd will not be able to supply it.
-
- Another option is:
- 5815 stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/x11vnc \
- -inetd -httpdir /usr/local/share/x11vnc/classes/ssl \
- -oa /var/log/x11vnc-15.log -display WAIT:cmd=HTTPONCE
-
- (this also requires a feature found in x11vnc 0.8.4).
- _________________________________________________________________
-
- Other Ideas:
-
- - The above schemes work, but they are a bit complicated with all of
- the rigging. There should be more elegant ways to configure Apache to
- do these, but we have not found them (please let us know if you
- discover something nice). However, once this scheme has been set up
- and is working it is easy to maintain and add/delete workstations,
- etc.
-
- - In general Apache is not required, but it makes things convenient.
- The firewall itself could do the port redirection via its firewall
- rules. Evidently different Internet-facing ports would be required for
- each workstation. This could be set up using iptables rules for
- example. If there were just one or two machines this would be the
- easiest method. For example:
- iptables -t nat -A PREROUTING -p tcp -d 24.35.46.57 --dport 5901 -j DNAT --to
--destination 192.168.1.2:5915
- iptables -t nat -A PREROUTING -p tcp -d 24.35.46.57 --dport 5902 -j DNAT --to
--destination 192.168.1.3:5915
-
- Where 24.35.46.57 is the internet IP address of the gateway. In this
- example 24.35.46.57:5901 is redirected to the internal machine
- 192.168.1.2:5915 and 24.35.46.57:5902 is redirected to another
- internal machine 192.168.1.3:5915, both running x11vnc -ssl ... in SSL
- mode. For this example, the user would point the web browser to, e.g.:
- https://24.35.46.57:5901/?PORT=5901
-
- or using the stunnel wrapper script:
- ss_vncviewer 24.35.46.57:1
-
- One can achieve similar things with dedicated firewall/routers (e.g.
- Linksys) using the device's web or other interface to configure the
- firewall.
-
- If the user may be coming out of a firewall using a proxy it may be
- better to redirect ports 443 and 563 (instead of 5901 and 5902) to the
- internal machines so that the user's proxy will allow CONNECTing to
- them.
-
- - The redirection could also be done at the application level using a
- TCP redirect program (e.g. ip_relay or fancier ones). Evidently more
- careful internal hostname checking, etc., could be performed by the
- special purpose application to add security. See connect_switch which
- is somewhat related.
-
- - One might imagine the ProxyPass could be done for the VNC traffic as
- well (for the ssl.conf case) to avoid the CONNECT proxying completely
- (which would be nice to avoid). Unfortunately we were not able to get
- this to work. Since HTTP is a request-response protocol (as opposed to
- a full bidirectional link required by VNC that CONNECT provides) this
- makes it difficult to do. It may be possible, but we haven't found out
- how yet.
-
- All of the x11vnc Java Viewer applet parameters are described in the
- file classes/ssl/README
-
- _________________________________________________________________
-
- Tricks for Better Response and reliability:
-
- The "original scheme" using httpd.conf and ssl.conf rewrites without
- urlPrefix and trustAllVncCerts above should work OK, but may lead to
- slow and/or unreliable loading of the applet and final connection to
- x11vnc. The following are what I do now to get better response and
- reliability. YMMV.
-
- The problem with the "original scheme" is that there is a point where
- the VNC Viewer applet can try up to 3 times to retrieve the x11vnc
- certificate, since it needs to get it to show it to you and ask you if
- you accept it. This can add about 45 seconds to the whole process
- (which takes 1 to 1.5 minutes with all the dialogs) since a couple of
- those connections must time out. The "trust" items in the config add a
- parameter trustAllVncCerts=yes similar to the forceProxy=yes
- parameter. This can cut the total time to the VNC password prompt down
- to 15 seconds which is pretty good. (Note by ignoring the certificate
- this does not protect against man-in-the-middle attacks which are
- rare, but maybe the won't be so rare in the future... see
- dsniff/webmitm and cain)
-
- First make sure the x11vnc SSL certificate+key is the same as
- Apache's. (otherwise you may get one extra dialog and/or one extra
- connection that has to time out).
-
- The following RewriteRule's are the same now advocated in the
- instructions above.
-
- The httpsPort and urlPrefix= parameters give hints to the applet to
- improve connecting: This is what goes in httpd.conf:
- RewriteEngine On
- RewriteRule /vnc/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1 [R,NE]
- RewriteRule /vnc/trust/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&trustAllVncCerts=yes [R,NE]
- RewriteRule /vnc/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes [R,NE]
- RewriteRule /vnc/trust/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$1+5915&PO
-RT=563&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes&trustAllVncCerts=yes [R,NE]
-
- The httpsPort and urlPrefix provide useful hints to the VNC Viewer
- applet when it connects to x11vnc to glean information about Proxies,
- certificates, etc.
-
- This is what goes into ssl.conf:
- RewriteEngine On
- RewriteRule /vnc/([^/]+)$ /vnc/$1/index.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vnc_2F_$1 [R,NE]
- RewriteRule /vnc/proxy/([^/]+)$ /vnc/$1/proxy.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vnc_2F_$1&forceProxy=yes [R,NE]
- RewriteRule /vncs/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1 [R,NE]
- RewriteRule /vncs/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes [R,NE]
- RewriteRule /vncs/trust/([^/]+)$ /vncs/$1/index.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&trustAllVncCerts=yes [R,NE
-]
- RewriteRule /vncs/trust/proxy/([^/]+)$ /vncs/$1/proxy.vnc?CONNECT=$1+5915&P
-ORT=563&httpsPort=443&GET=1&urlPrefix=_2F_vncs_2F_$1&forceProxy=yes&trustAllVnc
-Certs=yes [R,NE]
-
- The rest is the same.
-
- The httpsPort and urlPrefix and GET provide useful hints to the VNC
- Viewer applet when it connects to x11vnc to glean information about
- Proxies, certificates, etc, and also for the ultimate VNC connection
- (GET speeds this up by sending a special HTTP GET to cause x11vnc to
- immediately switch to the VNC protocol).
-
- To turn these into URLs, as was done above, take the string in the
- RewriteRule, e.g. /vncs and turn it into
- https://gateway/vncs/machinename Similarly for non-https:
- http://gateway:563/vnc/machinename
-
- If you use the 'trust' ones, you are performing NO checks, visual or
- otherwise, on the VNC SSL certificate. It is trusted without question.
- This speeds things up because it avoids a dialog about certificates,
- but of course has some risk WRT Man in the Middle attacks. I don't
- recommend them. It is better to use /vnc or /vncs and the first time
- you connect carefully check the Certificate and then tell your Browser
- and Java Virtual Machine to trust the certificate 'Always'. Then if
- you later get an unexpected dialog, you know something is wrong.
- Nearly always it is just a changed or expired certificate, but better
- safe than sorry...
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/enhanced_tightvnc_viewer.html:
-
-
- _________________________________________________________________
-
-Enhanced TightVNC Viewer (SSVNC: SSL/SSH VNC viewer)
-
- (To Downloads) (To Quick Start)
-
- [ssvnc.gif] [ssvnc_windows.gif] [ssvnc_macosx.gif] . .
-
-
- The Enhanced TightVNC Viewer, SSVNC, adds encryption security to VNC
- connections.
-
- The package provides a GUI for Windows, Mac OS X, and Unix that
- automatically starts up an STUNNEL SSL tunnel for SSL or ssh/plink for
- SSH connections to any VNC server, such as x11vnc, and then launches
- the VNC Viewer to use the encrypted tunnel.
-
- The x11vnc server has built-in SSL support, however SSVNC can make SSL
- encrypted VNC connections to any VNC Server if they are running an SSL
- tunnel, such as STUNNEL or socat, at their end. SSVNC's SSH tunnel
- will work to any VNC Server host running sshd that you can log into.
-
- The Enhanced TightVNC Viewer package started as a project to add some
- patches to the long neglected Unix TightVNC Viewer. However, now the
- front-end GUI, encryption, and wrapper scripts features possibly
- outweigh the Unix TightVNC Viewer improvements (see the lists below to
- compare).
-
- The SSVNC Unix vncviewer can also be run without the SSVNC encryption
- GUI as an enhanced replacement for the xvncviewer, xtightvncviewer,
- etc., viewers.
-
- In addition to normal SSL, SSVNC also supports the VeNCrypt SSL/TLS
- and Vino/ANONTLS encryption extensions to VNC on Unix, Mac OS X, and
- Windows. Via the provided SSVNC VeNCrypt bridge, VeNCrypt and ANONTLS
- encryption also works with any third party VNC Viewer (e.g. RealVNC,
- TightVNC, UltraVNC, etc...) you select via 'Change VNC Viewer'.
-
- The short name for this project is "ssvnc" for SSL/SSH VNC Viewer.
- This is the name of the command to start it.
-
- There is a simplified SSH-Only mode (sshvnc). And an even more
- simplified Terminal-Services mode (tsvnc) for use with x11vnc on the
- remote side.
-
- The tool has many additional features; see the descriptions below.
-
- It is a self-contained bundle, you could carry it around on, say, a
- USB memory stick / flash drive for secure VNC viewing from almost any
- machine, Unix, Mac OS X, and Windows (and if you create a directory
- named "Home" in the toplevel ssvnc directory on the drive your VNC
- profiles and certs will be kept there as well). For Unix, there is
- also a conventional source tarball to build and install in the normal
- way and not use a pre-built bundle.
-
- _________________________________________________________________
-
- Announcements:
-
- Important: If you created any SSL certificates with SSVNC (or anything
- else) on a Debian or Ubuntu system from Sept. 2006 through May 2008,
- then those keys are likely extremely weak and can be easily cracked.
- The certificate files should be deleted and recreated on a non-Debian
- system or an updated one. See
- http://www.debian.org/security/2008/dsa-1571 for details. The same
- applies to SSH keys.
-
- Please read this information on using SSVNC on workstations with
- Untrusted Local Users.
-
- _________________________________________________________________
-
- Feature List:
-
- Wrapper scripts and a tcl/tk GUI were written to create these features
- for Unix, Mac OS X, and Windows:
- * SSL support for connections using the bundled stunnel program.
- * Automatic SSH connections from the GUI (system ssh is used on Unix
- and MacOS X; bundled plink is used on Windows)
- * Ability to Save and Load VNC profiles for different hosts.
- * You can also use your own VNC Viewer, e.g. UltraVNC or RealVNC,
- with the SSVNC encryption GUI front-end if you prefer.
- * Create or Import SSL Certificates and Private Keys.
- * Reverse (viewer listening) VNC connections via SSL and SSH.
- * VeNCrypt SSL/TLS VNC encryption support (used by VeNCrypt, QEMU,
- ggi, libvirt/virt-manager/xen, vinagre/gvncviewer/gtk-vnc)
- * ANONTLS SSL/TLS VNC encryption support (used by Vino)
- * VeNCrypt and ANONTLS are also enabled for any 3rd party VNC Viewer
- (e.g. RealVNC, TightVNC, UltraVNC ...) on Unix, MacOSX, and
- Windows via the provided SSVNC VeNCrypt Viewer Bridge tool (use
- 'Change VNC Viewer' to select the one you want.)
- * Support for Web Proxies, SOCKS Proxies, and the UltraVNC repeater
- proxy (e.g. repeater://host:port+ID:1234). Multiple proxies may be
- chained together (3 max).
- * Support for SSH Gateway connections and non-standard SSH ports.
- * Automatic Service tunnelling via SSH for CUPS and SMB Printing,
- ESD/ARTSD Audio, and SMB (Windows/Samba) filesystem mounting.
- * Sets up any additional SSH port redirections that you want.
- * Zeroconf (aka Bonjour) is used on Unix and Mac OS X to find VNC
- servers on your local network if the avahi-browse or dns-sd
- program is available and in your PATH.
- * Port Knocking for "closed port" SSH/SSL connections. In addition
- to a simple fixed port sequence and one-time-pad implementation, a
- hook is also provided to run any port knocking client before
- connecting.
- * Support for native MacOS X usage with bundled Chicken of the VNC
- viewer (the Unix X11 viewer is also provided for MacOS X, and is
- better IMHO. It is now the default on MacOS X.)
- * Dynamic VNC Server Port determination and redirection (using ssh's
- builtin SOCKS proxy, ssh -D) for servers like x11vnc that print
- out PORT= at startup.
- * Unix Username and Password entry for use with "x11vnc -unixpw"
- type login dialogs.
- * Simplified mode launched by command "sshvnc" that is SSH Only.
- * Simplified mode launched by command "tsvnc" that provides a VNC
- "Terminal Services" mode (uses x11vnc on the remote side).
- * IPv6 support for all connection modes on Unix, MacOSX, and
- Windows.
-
- Patches to TightVNC 1.3.9 vnc_unixsrc tree were created for Unix
- TightVNC Viewer improvements (these only apply to the Unix VNC viewer,
- including MacOSX XQuartz):
- * rfbNewFBSize VNC support (dynamic screen resizing)
- * Client-side Scaling of the Desktop in the viewer.
- * ZRLE VNC encoding support (RealVNC's encoding)
- * Support for the ZYWRLE encoding, a wavelet based extension to ZRLE
- to improve compression of motion video and photo regions.
- * TurboVNC support (VirtualGL's modified TightVNC encoding; requires
- TurboJPEG library)
- * Pipelined Updates of the framebuffer as in TurboVNC (asks for the
- next update before the current one has finished downloading; this
- gives some speedup on high latency connections.)
- * Cursor alphablending with x11vnc at 32bpp (-alpha option)
- * Option "-unixpw ..." for use with "x11vnc -unixpw" type login
- dialogs.
- * Support for UltraVNC extensions: 1/n Server side scaling, Text
- Chat, Single Window, Disable Server-side Input. Both UltraVNC and
- x11vnc servers support these extensions.
- * UltraVNC File Transfer via an auxiliary Java helper program (java
- must be in $PATH). Note that the x11vnc server also supports
- UltraVNC file transfer.
- * Connection support for the UltraVNC repeater proxy (-repeater
- option).
- * Support for UltraVNC Single Click operation. (both unencrypted: SC
- I, and SSL encrypted: SC III)
- * Support for UltraVNC DSM Encryption Plugin symmetric encryption
- mode. (ARC4, AESV2, MSRC4, and SecureVNC)
- * Support for UltraVNC MS-Logon authentication (NOTE: the UltraVNC
- MS-Logon key exchange implementation is very weak; an eavesdropper
- on the network can recover your Windows password easily in a few
- seconds; you need to use an additional encrypted tunnel with
- MS-Logon.)
- * Support for symmetric encryption (including blowfish and 3des
- ciphers) to Non-UltraVNC Servers. Any server using the same
- encryption method will work, e.g.: x11vnc -enc blowfish:./my.key
- * Instead of hostname:display one can also supply "exec=command
- args..." to connect the viewer to the stdio of an external command
- (e.g. stunnel or socat) rather than using a TCP/IP socket. Unix
- domain sockets, e.g. /path/to/unix/socket, and a previously opened
- file descriptor fd=0, work too.
- * Local Port Protections for STUNNEL and SSH: avoid having for long
- periods of time a listening port on the the local (VNC viewer)
- side that redirects to the remote side.
- * Reverse (viewer listening) VNC connections can show a Popup dialog
- asking whether to accept the connection or not (-acceptpopup.) The
- extra info provided by UltraVNC Single Click reverse connections
- is also supported (-acceptpopupsc)
- * Extremely low color modes: 64 and 8 colors in 8bpp
- (-use64/-bgr222, -use8/-bgr111)
- * Medium color mode: 16bpp mode on a 32bpp Viewer display
- (-16bpp/-bgr565)
- * For use with x11vnc's client-side caching -ncache method use the
- cropping option -ycrop n. This will "hide" the large pixel buffer
- cache below the actual display. Set to the actual height or use -1
- for autodetection (also, tall screens, H > 2*W, are autodetected
- by default).
- * Escape Keys: specify a set of modifier keys so that when they are
- all pressed down you can invoke Popup menu actions via keystrokes.
- I.e., a set of 'Hot Keys'. One can also pan (move) the desktop
- inside the viewport via Arrow keys or a mouse drag.
- * Scrollbar width setting: -sbwidth n, the default is very thin, 2
- pixels, for less distracting -ycrop usage.
- * Selection text sending and receiving can be fine-tuned with the
- -sendclipboard, -sendalways, and -recvtext options.
- * TightVNC compression and quality levels are automatically set
- based on observed network latency (n.b. not bandwidth.)
- * Improvements to the Popup menu, all of these can now be changed
- dynamically via the menu: ViewOnly, Toggle Bell, CursorShape
- updates, X11 Cursor, Cursor Alphablending, Toggle Tight/ZRLE,
- Toggle JPEG, FullColor/16bpp/8bpp (256/64/8 colors), Greyscale for
- low color modes, Scaling the Viewer resolution, Escape Keys,
- Pipeline Updates, and others, including UltraVNC extensions.
- * Maintains its own BackingStore if the X server does not.
- * The default for localhost:0 connections is not raw encoding since
- same-machine connections are pretty rare. Default assumes you are
- using a SSL or SSH tunnel. Use -rawlocal to revert.
- * XGrabServer support for fullscreen mode, for old window managers
- (-grab/-graball option).
- * Fix for Popup menu positioning for old window managers (-popupfix
- option).
- * The VNC Viewer ssvncviewer supports IPv6 natively (no helpers
- needed.)
-
- The list of 3rd party software bundled in the archive files:
- * TightVNC Viewer (windows, unix, macosx)
- * Chicken of the VNC Viewer (macosx)
- * Stunnel (windows, unix, macosx)
- * Putty/Plink/Pageant (windows)
- * OpenSSL (windows)
- * esound (windows)
-
- These are all self-contained in the bundle directory: they will not be
- installed on your system. Just un-zip or un-tar the file you
- downloaded and run the frontend ssvnc straight from its directory.
- Alternatively, on Unix you can use the conventional source tarball.
-
- _________________________________________________________________
-
- Here is the Quick Start info from the README for how to setup and use
- SSVNC:
-Quick Start:
------------
-
-Unix and Mac OS X:
-
- Inside a Terminal do something like the following.
-
- Unpack the archive:
-
- % gzip -dc ssvnc-1.0.29.tar.gz | tar xvf -
-
- Run the GUI:
-
- % ./ssvnc/Unix/ssvnc (for Unix)
-
- % ./ssvnc/MacOSX/ssvnc (for Mac OS X)
-
- The smaller file "ssvnc_no_windows-1.0.29.tar.gz"
- could have been used as well.
-
- On MacOSX you could also click on the SSVNC app icon in the Finder.
-
- On MacOSX if you don't like the Chicken of the VNC (e.g. no local
- cursors, no screen size rescaling, and no password prompting), and you
- have the XDarwin X server installed, you can set DISPLAY before starting
- ssvnc (or type DISPLAY=... in Host:Disp and hit Return). Then our
- enhanced TightVNC viewer will be used instead of COTVNC.
- Update: there is now a 'Use X11 vncviewer on MacOSX' under Options ...
-
-
- If you want a SSH-only tool (without the distractions of SSL) run
- the command:
-
- sshvnc
-
- instead of "ssvnc". Or click "SSH-Only Mode" under Options.
- Control-h will toggle between the two modes.
-
-
- If you want a simple VNC Terminal Services only mode (requires x11vnc
- on the remote server) run the command:
-
- tsvnc
-
- instead of "ssvnc". Or click "Terminal Services" under Options.
- Control-t will toggle between the two modes.
-
- "tsvnc profile-name" and "tsvnc user@hostname" work too.
-
-
-Unix/MacOSX Install:
-
- There is no standard install for the bundles, but you can make
- symlinks like so:
-
- cd /a/directory/in/PATH
- ln -s /path/to/ssvnc/bin/{s,t}* .
-
- Or put /path/to/ssvnc/bin, /path/to/ssvnc/Unix, or /path/to/ssvnc/MacOSX
- in your PATH.
-
- For the conventional source tarball it will compile and install, e.g.:
-
- gzip -dc ssvnc-1.0.29.src.tar.gz | tar xvf -
- cd ssvnc-1.0.29
- make config
- make all
- make PREFIX=/my/install/dir install
-
- then have /my/install/dir/bin in your PATH.
-
-
-
-Windows:
-
- Unzip, using WinZip or a similar utility, the zip file:
-
- ssvnc-1.0.29.zip
-
- Run the GUI, e.g.:
-
- Start -> Run -> Browse
-
- and then navigate to
-
- .../ssvnc/Windows/ssvnc.exe
-
- select Open, and then OK to launch it.
-
- The smaller file "ssvnc_windows_only-1.0.29.zip"
- could have been used as well.
-
- You can make a Windows shortcut to this program if you want to.
-
- See the Windows/README.txt for more info.
-
-
- If you want a SSH-only tool (without the distractions of SSL) run
- the command:
-
- sshvnc.bat
-
- Or click "SSH-Only Mode" under Options.
-
-
- If you want a simple VNC Terminal Services only mode (requires x11vnc
- on the remote server) run the command:
-
- tsvnc.bat
-
- Or click "Terminal Services" under Options. Control-t will toggle
- between the two modes. "tsvnc profile-name" and "tsvnc user@hostname"
- work too.
-
- _________________________________________________________________
-
- You can read all of the SSVNC GUI's Online Help Text here.
- _________________________________________________________________
-
- The bundle unpacks a directory/folder named: ssvnc. It contains these
- programs to launch the GUI:
- Windows/ssvnc.exe for Windows
- MacOSX/ssvnc for Mac OS X
- Unix/ssvnc for Unix
-
- (the Mac OS X and Unix launchers are simply links to the bin
- directory). See the README for more information.
-
- The SSH-Only mode launcher program has name sshvnc. The Terminal
- Services mode launcher program (assumes x11vnc 0.8.4 or later and Xvfb
- installed on the server machine) has name tsvnc.
-
- The Viewer SSL support is done via a wrapper script (bin/ssvnc_cmd
- that calls bin/util/ss_vncviewer) that starts up the STUNNEL tunnel
- first and then starts the TightVNC viewer pointed at that tunnel. The
- bin/ssvnc program is a GUI front-end to that script. See this FAQ for
- more details on SSL tunnelling. In SSH connection mode, the wrappers
- start up SSH appropriately.
-
-
- Memory Stick Usage: If you create a directory named "Home" in that
- toplevel ssvnc directory then that will be used as the base for
- storing VNC profiles and certificates. Also, for convenience, if you
- first run the command with "." as an argument (e.g. "ssvnc .") it will
- automatically create the "Home" directory for you. This is handy if
- you want to place SSVNC on a USB flash drive that you carry around for
- mobile use and you want the profiles you create to stay with the drive
- (otherwise you'd have to browse to the drive directory each time you
- load or save).
-
- One user on Windows created a BAT file to launch SSVNC and needed to
- do this to get the Home directory correct:
-cd \ssvnc\Windows
-start \ssvnc\Windows\ssvnc.exe
-
- (an optional profile name can be supplied to the ssvnc.exe line)
-
- WARNING: if you use ssvnc from an "Internet Cafe", i.e. some untrusted
- computer, please be aware that someone may have set up that machine to
- be capturing your keystrokes, etc.
-
-
- SSH-Only version: The command "sshvnc" can be run instead of "ssvnc"
- to get an SSH-only version of the tool:
-
- [sshvnc.gif]
-
- These also work: "sshvnc myprofile" and "sshvnc user@hostname". To
- switch from the regular SSVNC mode, click "SSH-Only Mode" under
- Options. This mode is less distracting if you never plan to use SSL,
- manage certificates, etc.
-
-
- Terminal Services Only: The command "tsvnc" can be run instead of
- "ssvnc" to get a "Terminal Services" only version of the tool:
-
- [tsvnc.gif]
-
- These also work: "tsvnc myprofile" and "tsvnc user@hostname". To
- switch from the regular SSVNC mode, click "Terminal Services" under
- Options.
-
- This mode requires x11vnc (0.9.3 or later) installed on the remote
- machine to find, create, and manage the user sessions. SSH is used to
- create the encrypted and authenticated tunnel. The Xvfb (virtual
- framebuffer X server) program must also be installed on the remote
- system. However tsvnc will also connect to a real X session (i.e. on
- the physical hardware) if you are already logged into the X session;
- this is a useful access mode and does not require Xvfb on the remote
- system.
-
- This mode should be very easy for beginner users to understand and
- use. On the remote end you only need to have x11vnc and Xvfb available
- in $PATH, and on the local end you just run something like:
- tsvnc myname@myhost.com
-
- (or start up the tsvnc GUI first and then enter myname@myhost.com and
- press "Connect").
-
- Normally the Terminal Services sessions created are virtual (RAM-only)
- ones (e.g. Xvfb, Xdummy, or Xvnc), however a nice feature is if you
- have a regular X session (i.e displaying on the physical hardware) on
- the remote machine that you are ALREADY logged into, then the x11vnc
- run from tsvnc will find it for you as well.
-
- Also, there is setting "X Login" under Advanced Options that allows
- you to attach to a real X server with no one logged in yet (i.e.
- XDM/GDM/KDM Login Greeter screen) as long as you have sudo(1)
- permission on the remote machine.
-
- Nice features to soon to be added to the tsvnc mode are easy CUPS
- printing (working fairly well) and Sound redirection (needs much work)
- of the Terminal Services Desktop session. It is easier in tsvnc mode
- because the entire desktop session can be started with the correct
- environment. ssvnc tries to handle the general case of an already
- started desktop and that is more difficult.
-
-
- Proxies: Web proxies, SOCKS proxies, and the UltraVNC repeater proxy
- are supported to allow the SSVNC connection to go through the proxy to
- the otherwise unreachable VNC Server. SSH gateway machines can be used
- in the same way. Read more about SSVNC proxy support here.
-
-
- Dynamic VNC Server Port determination: If you are running SSVNC on
- Unix and are using SSH to start the remote VNC server and the VNC
- server prints out the line "PORT=NNNN" to indicate which dynamic port
- it is using (x11vnc does this), then if you prefix the SSH command
- with "PORT=" SSVNC will watch for the PORT=NNNN line and uses ssh's
- built in SOCKS proxy (ssh -D ...) to connect to the dynamic VNC server
- port through the SSH tunnel. For example:
- VNC Host:Display user@somehost.com
- Remote SSH Command: PORT= x11vnc -find
-
- or "PORT= x11vnc -display :0 -localhost", etc. Or use "P= x11vnc ..."
-
- There is also code to detect the display of the regular Unix
- vncserver(1). It extracts the display (and hence port) from the lines
- "New 'X' desktop is hostname:4" and also "VNC server is already
- running as :4". So you can use something like:
- PORT= vncserver; sleep 15
-or: PORT= vncserver :4; sleep 15
-
- the latter is preferred because when you reconnect with it will find
- the already running one. The former one will keep creating new X
- sessions if called repeatedly.
-
- If you use PORT= on Windows, a large random port is selected instead
- and the -rfbport option is passed to x11vnc (it does not work with
- vncserver).
-
-
-
- Patches for Unix Tightvnc viewer:
-
- The rfbNewFBSize support allows the enhanced TightVNC Unix viewer to
- resize when the server does (e.g. "x11vnc -R scale=3/4" remote control
- command).
-
- The cursor alphablending is described here.
-
- The RealVNC ZRLE encoding is supported, in addition to some low colors
- modes (16bpp and 8bpp at 256, 64, and even 8 colors, for use on very
- slow connections). Greyscales are also enabled for the low color
- modes.
-
- The Popup menu (F8) is enhanced with the ability to change many things
- on the fly. F9 is added as a shortcut to toggle FullScreen mode.
-
- Client Side Caching: The x11vnc client-side caching is handled nicely
- by this viewer. The very large pixel cache below the actual display in
- this caching method is distracting. Our Unix VNC viewer will
- automatically try to autodetect the actual display height if the
- framebuffer is very tall (more than twice as high as it is wide). One
- can also set the height to the known value via -ycrop n, or use -ycrop
- -1 to force autodection. In fullscreen mode one is not possible to
- scroll down to the pixel cache region. In non-fullscreen mode the
- window manager frame is "shrink-wrapped" around the actual screen
- display. You can still scroll down to the pixel cache region. The
- scrollbars are set to be very thin (2 pixels) to be less distracting.
- Use the -sbwidth n to make them wider.
-
- Probably nobody is interested in the grabserver patch for old window
- managers when the viewer is in fullscreen mode... This and some other
- unfixed bugs have been fixed in our patches (fullscreen toggle works
- with KDE, -x11cursor has been fixed, and the dot cursor has been made
- smaller).
-
- From the -help output:
-SSVNC Viewer (based on TightVNC viewer version 1.3.9)
-
-Usage: vncviewer [<OPTIONS>] [<HOST>][:<DISPLAY#>]
- vncviewer [<OPTIONS>] [<HOST>][::<PORT#>]
- vncviewer [<OPTIONS>] exec=[CMD ARGS...]
- vncviewer [<OPTIONS>] fd=n
- vncviewer [<OPTIONS>] /path/to/unix/socket
- vncviewer [<OPTIONS>] -listen [<DISPLAY#>]
- vncviewer -help
-
-<OPTIONS> are standard Xt options, or:
- -via <GATEWAY>
- -shared (set by default)
- -noshared
- -viewonly
- -fullscreen
- -noraiseonbeep
- -passwd <PASSWD-FILENAME> (standard VNC authentication)
- -user <USERNAME> (Unix login authentication)
- -encodings <ENCODING-LIST> (e.g. "tight,copyrect")
- -bgr233
- -owncmap
- -truecolour
- -depth <DEPTH>
- -compresslevel <COMPRESS-VALUE> (0..9: 0-fast, 9-best)
- -quality <JPEG-QUALITY-VALUE> (0..9: 0-low, 9-high)
- -nojpeg
- -nocursorshape
- -x11cursor
- -autopass
-
-Option names may be abbreviated, e.g. -bgr instead of -bgr233.
-See the manual page for more information.
-
-
-Enhanced TightVNC viewer (SSVNC) options:
-
- URL http://www.karlrunge.com/x11vnc/ssvnc.html
-
- Note: ZRLE and ZYWRLE encodings are now supported.
-
- Note: F9 is shortcut to Toggle FullScreen mode.
-
- Note: In -listen mode set the env var. SSVNC_MULTIPLE_LISTEN=1
- to allow more than one incoming VNC server at a time.
- This is the same as -multilisten described below. Set
- SSVNC_MULTIPLE_LISTEN=MAX:n to allow no more than "n"
- simultaneous reverse connections.
-
- Note: If the host:port is specified as "exec=command args..."
- then instead of making a TCP/IP socket connection to the
- remote VNC server, "command args..." is executed and the
- viewer is attached to its stdio. This enables tunnelling
- established via an external command, e.g. an stunnel(8)
- that does not involve a listening socket. This mode does
- not work for -listen reverse connections.
-
- If the host:port is specified as "fd=n" then it is assumed
- n is an already opened file descriptor to the socket. (i.e
- the parent did fork+exec)
-
- If the host:port contains a '/' it is interpreted as a
- unix-domain socket (AF_LOCAL insead of AF_INET)
-
- -multilisten As in -listen (reverse connection listening) except
- allow more than one incoming VNC server to be connected
- at a time. The default for -listen of only one at a
- time tries to play it safe by not allowing anyone on
- the network to put (many) desktops on your screen over
- a long window of time. Use -multilisten for no limit.
-
- -acceptpopup In -listen (reverse connection listening) mode when
- a reverse VNC connection comes in show a popup asking
- whether to Accept or Reject the connection. The IP
- address of the connecting host is shown. Same as
- setting the env. var. SSVNC_ACCEPT_POPUP=1.
-
- -acceptpopupsc As in -acceptpopup except assume UltraVNC Single
- Click (SC) server. Retrieve User and ComputerName
- info from UltraVNC Server and display in the Popup.
-
- -use64 In -bgr233 mode, use 64 colors instead of 256.
- -bgr222 Same as -use64.
-
- -use8 In -bgr233 mode, use 8 colors instead of 256.
- -bgr111 Same as -use8.
-
- -16bpp If the vnc viewer X display is depth 24 at 32bpp
- request a 16bpp format from the VNC server to cut
- network traffic by up to 2X, then tranlate the
- pixels to 32bpp locally.
- -bgr565 Same as -16bpp.
-
- -grey Use a grey scale for the 16- and 8-bpp modes.
-
- -alpha Use alphablending transparency for local cursors
- requires: x11vnc server, both client and server
- must be 32bpp and same endianness.
-
- -scale str Scale the desktop locally. The string "str" can
- a floating point ratio, e.g. "0.9", or a fraction,
- e.g. "3/4", or WxH, e.g. 1280x1024. Use "fit"
- to fit in the current screen size. Use "auto" to
- fit in the window size. "str" can also be set by
- the env. var. SSVNC_SCALE.
-
- If you observe mouse trail painting errors, enable
- X11 Cursor mode (either via Popup or -x11cursor.)
-
- Note that scaling is done in software and so can be
- slow and requires more memory. Some speedup Tips:
-
- ZRLE is faster than Tight in this mode. When
- scaling is first detected, the encoding will
- be automatically switched to ZRLE. Use the
- Popup menu if you want to go back to Tight.
- Set SSVNC_PRESERVE_ENCODING=1 to disable this.
-
- Use a solid background on the remote side.
- (e.g. manually or via x11vnc -solid ...)
-
- If the remote server is x11vnc, try client
- side caching: x11vnc -ncache 10 ...
-
- -ycrop n Only show the top n rows of the framebuffer. For
- use with x11vnc -ncache client caching option
- to help "hide" the pixel cache region.
- Use a negative value (e.g. -1) for autodetection.
- Autodetection will always take place if the remote
- fb height is more than 2 times the width.
-
- -sbwidth n Scrollbar width for x11vnc -ncache mode (-ycrop),
- default is very narrow: 2 pixels, it is narrow to
- avoid distraction in -ycrop mode.
-
- -nobell Disable bell.
-
- -rawlocal Prefer raw encoding for localhost, default is
- no, i.e. assumes you have a SSH tunnel instead.
-
- -notty Try to avoid using the terminal for interactive
- responses: use windows for messages and prompting
- instead. Messages will also be printed to terminal.
-
- -sendclipboard Send the X CLIPBOARD selection (i.e. Ctrl+C,
- Ctrl+V) instead of the X PRIMARY selection (mouse
- select and middle button paste.)
-
- -sendalways Whenever the mouse enters the VNC viewer main
- window, send the selection to the VNC server even if
- it has not changed. This is like the Xt resource
- translation SelectionToVNC(always)
-
- -recvtext str When cut text is received from the VNC server,
- ssvncviewer will set both the X PRIMARY and the
- X CLIPBOARD local selections. To control which
- is set, specify 'str' as 'primary', 'clipboard',
- or 'both' (the default.)
-
- -graball Grab the entire X server when in fullscreen mode,
- needed by some old window managers like fvwm2.
-
- -popupfix Warp the popup back to the pointer position,
- needed by some old window managers like fvwm2.
- -sendclipboard Send the X CLIPBOARD selection (i.e. Ctrl+C,
- Ctrl+V) instead of the X PRIMARY selection (mouse
- select and middle button paste.)
-
- -sendalways Whenever the mouse enters the VNC viewer main
- window, send the selection to the VNC server even if
- it has not changed. This is like the Xt resource
- translation SelectionToVNC(always)
-
- -recvtext str When cut text is received from the VNC server,
- ssvncviewer will set both the X PRIMARY and the
- X CLIPBOARD local selections. To control which
- is set, specify 'str' as 'primary', 'clipboard',
- or 'both' (the default.)
-
- -graball Grab the entire X server when in fullscreen mode,
- needed by some old window managers like fvwm2.
-
- -popupfix Warp the popup back to the pointer position,
- needed by some old window managers like fvwm2.
-
- -grabkbd Grab the X keyboard when in fullscreen mode,
- needed by some window managers. Same as -grabkeyboard.
- -grabkbd is the default, use -nograbkbd to disable.
-
- -bs, -nobs Whether or not to use X server Backingstore for the
- main viewer window. The default is to not, mainly
- because most Linux, etc, systems X servers disable
- *all* Backingstore by default. To re-enable it put
-
- Option "Backingstore"
-
- in the Device section of /etc/X11/xorg.conf.
- In -bs mode with no X server backingstore, whenever an
- area of the screen is re-exposed it must go out to the
- VNC server to retrieve the pixels. This is too slow.
-
- In -nobs mode, memory is allocated by the viewer to
- provide its own backing of the main viewer window. This
- actually makes some activities faster (changes in large
- regions) but can appear to "flash" too much.
-
- -noshm Disable use of MIT shared memory extension (not recommended
-)
-
- -termchat Do the UltraVNC chat in the terminal vncviewer is in
- instead of in an independent window.
-
- -unixpw str Useful for logging into x11vnc in -unixpw mode. "str" is a
- string that allows many ways to enter the Unix Username
- and Unix Password. These characters: username, newline,
- password, newline are sent to the VNC server after any VNC
- authentication has taken place. Under x11vnc they are
- used for the -unixpw login. Other VNC servers could do
- something similar.
-
- You can also indicate "str" via the environment
- variable SSVNC_UNIXPW.
-
- Note that the Escape key is actually sent first to tell
- x11vnc to not echo the Unix Username back to the VNC
- viewer. Set SSVNC_UNIXPW_NOESC=1 to override this.
-
- If str is ".", then you are prompted at the command line
- for the username and password in the normal way. If str is
- "-" the stdin is read via getpass(3) for username@password.
- Otherwise if str is a file, it is opened and the first line
- read is taken as the Unix username and the 2nd as the
- password. If str prefixed by "rm:" the file is removed
- after reading. Otherwise, if str has a "@" character,
- it is taken as username@password. Otherwise, the program
- exits with an error. Got all that?
-
- -repeater str This is for use with UltraVNC repeater proxy described
- here: http://www.uvnc.com/addons/repeater.html. The "str"
- is the ID string to be sent to the repeater. E.g. ID:1234
- It can also be the hostname and port or display of the VNC
- server, e.g. 12.34.56.78:0 or snoopy.com:1. Note that when
- using -repeater, the host:dpy on the cmdline is the repeate
-r
- server, NOT the VNC server. The repeater will connect you.
-
- Example: vncviewer ... -repeater ID:3333 repeat.host:5900
- Example: vncviewer ... -repeater vhost:0 repeat.host:5900
-
- Use, e.g., '-repeater SCIII=ID:3210' if the repeater is a
- Single Click III (SSL) repeater (repeater_SSL.exe) and you
- are passing the SSL part of the connection through stunnel,
- socat, etc. This way the magic UltraVNC string 'testB'
- needed to work with the repeater is sent to it.
-
- -rfbversion str Set the advertised RFB version. E.g.: -rfbversion 3.6
- For some servers, e.g. UltraVNC this needs to be done.
-
- -ultradsm UltraVNC has symmetric private key encryption DSM plugins:
- http://www.uvnc.com/features/encryption.html. It is assumed
- you are using a unix program (e.g. our ultravnc_dsm_helper)
- to encrypt and decrypt the UltraVNC DSM stream. IN ADDITION
- TO THAT supply -ultradsm to tell THIS viewer to modify the
- RFB data sent so as to work with the UltraVNC Server. For
- some reason, each RFB msg type must be sent twice under DSM
-.
-
- -mslogon user Use Windows MS Logon to an UltraVNC server. Supply the
- username or "1" to be prompted. The default is to
- autodetect the UltraVNC MS Logon server and prompt for
- the username and password.
-
- IMPORTANT NOTE: The UltraVNC MS-Logon Diffie-Hellman
- exchange is very weak and can be brute forced to recover
- your username and password in a few seconds of CPU time.
- To be safe, be sure to use an additional encrypted tunnel
- (e.g. SSL or SSH) for the entire VNC session.
-
- -chatonly Try to be a client that only does UltraVNC text chat. This
- mode is used by x11vnc to present a chat window on the
- physical X11 console (i.e. chat with the person at the
- display).
-
- -env VAR=VALUE To save writing a shell script to set environment variables
-,
- specify as many as you need on the command line. For
- example, -env SSVNC_MULTIPLE_LISTEN=MAX:5 -env EDITOR=vi
-
- -noipv6 Disable all IPv6 sockets. Same as VNCVIEWER_NO_IPV6=1.
-
- -noipv4 Disable all IPv4 sockets. Same as VNCVIEWER_NO_IPV4=1.
-
- -printres Print out the Ssvnc X resources (appdefaults) and then exit
- You can save them to a file and customize them (e.g. the
- keybindings and Popup menu) Then point to the file via
- XENVIRONMENT or XAPPLRESDIR.
-
- -pipeline Like TurboVNC, request the next framebuffer update as soon
- as possible instead of waiting until the end of the current
- framebuffer update coming in. Helps 'pipeline' the updates
-.
- This is currently the default, use -nopipeline to disable.
-
- -appshare Enable features for use with x11vnc's -appshare mode where
- instead of sharing the full desktop only the application's
- windows are shared. Viewer multilisten mode is used to
- create the multiple windows: -multilisten is implied.
- See 'x11vnc -appshare -help' more information on the mode.
-
- Features enabled in the viewer under -appshare are:
- Minimum extra text in the title, auto -ycrop is disabled,
- x11vnc -remote_prefix X11VNC_APPSHARE_CMD: message channel,
- x11vnc initial window position hints. See also Escape Keys
- below for additional key and mouse bindings.
-
- -escape str This sets the 'Escape Keys' modifier sequence and enables
- escape keys mode. When the modifier keys escape sequence
- is held down, the next keystroke is interpreted locally
- to perform a special action instead of being sent to the
- remote VNC server.
-
- Use '-escape default' for the default modifier sequence.
- (Unix: Alt_L,Super_L and MacOSX: Control_L,Meta_L)
-
- Here are the 'Escape Keys: Help+Set' instructions from the Popup Menu:
-
- Escape Keys: Enter a comma separated list of modifier keys to be the
- 'escape sequence'. When these keys are held down, the next keystroke is
- interpreted locally to invoke a special action instead of being sent to
- the remote VNC server. In other words, a set of 'Hot Keys'.
-
- To enable or disable this, click on 'Escape Keys: Toggle' in the Popup.
-
- Here is the list of hot-key mappings to special actions:
-
- r: refresh desktop b: toggle bell c: toggle full-color
- f: file transfer x: x11cursor z: toggle Tight/ZRLE
- l: full screen g: graball e: escape keys dialog
- s: scale dialog +: scale up (=) -: scale down (_)
- t: text chat a: alphablend cursor
- V: toggle viewonly Q: quit viewer 1 2 3 4 5 6: UltraVNC scale 1/n
-
- Arrow keys: pan the viewport about 10% for each keypress.
- PageUp / PageDown: pan the viewport by a screenful vertically.
- Home / End: pan the viewport by a screenful horizontally.
- KeyPad Arrow keys: pan the viewport by 1 pixel for each keypress.
- Dragging the Mouse with Button1 pressed also pans the viewport.
- Clicking Mouse Button3 brings up the Popup Menu.
-
- The above mappings are *always* active in ViewOnly mode, unless you set the
- Escape Keys value to 'never'.
-
- If the Escape Keys value below is set to 'default' then a default list of
- of modifier keys is used. For Unix it is: Alt_L,Super_L and for MacOSX it
- is Control_L,Meta_L. Note: the Super_L key usually has a Windows(TM) Flag
- on it. Also note the _L and _R mean the key is on the LEFT or RIGHT side
- of the keyboard.
-
- On Unix the default is Alt and Windows keys on Left side of keyboard.
- On MacOSX the default is Control and Command keys on Left side of keyboard.
-
- Example: Press and hold the Alt and Windows keys on the LEFT side of the
- keyboard and then press 'c' to toggle the full-color state. Or press 't'
- to toggle the ultravnc Text Chat window, etc.
-
- To use something besides the default, supply a comma separated list (or a
- single one) from: Shift_L Shift_R Control_L Control_R Alt_L Alt_R Meta_L
- Meta_R Super_L Super_R Hyper_L Hyper_R or Mode_switch.
-
-
- New Popup actions:
-
- ViewOnly: ~ -viewonly
- Disable Bell: ~ -nobell
- Cursor Shape: ~ -nocursorshape
- X11 Cursor: ~ -x11cursor
- Cursor Alphablend: ~ -alpha
- Toggle Tight/Hextile: ~ -encodings hextile...
- Toggle Tight/ZRLE: ~ -encodings zrle...
- Toggle ZRLE/ZYWRLE: ~ -encodings zywrle...
- Quality Level ~ -quality (both Tight and ZYWRLE)
- Compress Level ~ -compresslevel
- Disable JPEG: ~ -nojpeg (Tight)
- Pipeline Updates ~ -pipeline
-
- Full Color as many colors as local screen allows.
- Grey scale (16 & 8-bpp) ~ -grey, for low colors 16/8bpp modes only.
- 16 bit color (BGR565) ~ -16bpp / -bgr565
- 8 bit color (BGR233) ~ -bgr233
- 256 colors ~ -bgr233 default # of colors.
- 64 colors ~ -bgr222 / -use64
- 8 colors ~ -bgr111 / -use8
- Scale Viewer ~ -scale
- Escape Keys: Toggle ~ -escape
- Escape Keys: Help+Set ~ -escape
- Set Y Crop (y-max) ~ -ycrop
- Set Scrollbar Width ~ -sbwidth
- XGrabServer ~ -graball
-
- UltraVNC Extensions:
-
- Set 1/n Server Scale Ultravnc ext. Scale desktop by 1/n.
- Text Chat Ultravnc ext. Do Text Chat.
- File Transfer Ultravnc ext. File xfer via Java helper.
- Single Window Ultravnc ext. Grab and view a single window.
- (select then click on the window you want).
- Disable Remote Input Ultravnc ext. Try to prevent input and
- viewing of monitor at physical display.
-
- Note: the Ultravnc extensions only apply to servers that support
- them. x11vnc/libvncserver supports some of them.
-
- Send Clipboard not Primary ~ -sendclipboard
- Send Selection Every time ~ -sendalways
-
- Nearly all of these can be changed dynamically in the Popup menu
- (press F8 for it):
-
- [viewer_menu.gif] [unixviewer.jpg]
-
- _________________________________________________________________
-
- Windows:
-
- For Windows, SSL Viewer support is provided by a GUI Windows/ssvnc.exe
- that prompts for the VNC display and then starts up STUNNEL followed
- by the Stock TightVNC Windows Viewer. Both are bundled in the package
- for your convenience. The GUI has other useful features. When the
- connection is finished, you will be asked if you want to terminate the
- STUNNEL program. For SSH connections from Windows the GUI will use
- PLINK instead of STUNNEL.
-
- Unix and Mac OS X:
-
- Run the GUI (ssvnc, see above) and let me know how it goes.
- _________________________________________________________________
-
- Hopefully this tool will make it convenient for people to help test
- and use the built-in SSL support in x11vnc. Extra testing of this
- feature is much appreciated!! Thanks.
-
- Please Help Test the newly added features:
- * Automatic Service tunnelling via SSH for CUPS and SMB Printing
- * ESD/ARTSD Audio
- * SMB (Windows/Samba) filesystem mounting
-
- These allow you to print from the remote (VNC Server) machine to local
- printers, listen to sounds (with some limitations) from the remote VNC
- Server machine, and to mount your local Windows or Samba shares on the
- remote VNC Server machine. Basically these new features try to
- automate the tricks described here:
- http://www.karlrunge.com/x11vnc/faq.html#faq-smb-shares
- http://www.karlrunge.com/x11vnc/faq.html#faq-cups
- http://www.karlrunge.com/x11vnc/faq.html#faq-sound
- _________________________________________________________________
-
- Downloading: Downloads for this project are hosted at Sourceforge.net.
-
- Choose the archive file bundle that best suits you (e.g. no source
- code, windows only, unix only, zip, tar etc).
-
- A quick guide:
-
- On some flavor of Unix, e.g. Linux or Solaris? Use
- "ssvnc_unix_only" (or "ssvnc_no_windows" to recompile).
- On Mac OS X? Use "ssvnc_no_windows".
- On Windows? Use "ssvnc_windows_only".
- ssvnc_windows_only-1.0.28.zip Windows Binaries Only. No source included
- (6.2MB)
- ssvnc_no_windows-1.0.28.tar.gz Unix and Mac OS X Only. No Windows binarie
-s. Source included. (10.1MB)
- ssvnc_unix_only-1.0.28.tar.gz Unix Binaries Only. No source included
-. (7.2MB)
- ssvnc_unix_minimal-1.0.28.tar.gz Unix Minimal. You must supply your own vn
-cviewer and stunnel. (0.2MB)
-
- ssvnc-1.0.28.tar.gz All Unix, Mac OS X, and Windows binaries a
-nd source TGZ. (16.1MB)
- ssvnc-1.0.28.zip All Unix, Mac OS X, and Windows binaries a
-nd source ZIP. (16.4MB)
- ssvnc_all-1.0.28.zip All Unix, Mac OS X, and Windows binaries a
-nd source AND full archives in the zip dir. (19.2MB)
-
-
- Here is a conventional source tarball:
- ssvnc-1.0.28.src.tar.gz Conventional Source for SSVNC GUI and Unix
- VNCviewer (0.5MB)
-
- it will be of use to those who do not want the SSVNC
- "one-size-fits-all" bundles. For example, package/distro maintainers
- will find this more familiar and useful to them (i.e. they run: "make
- config; make all; make install"). Note that it does not include the
- stunnel source, and so has a dependency that the system stunnel is
- installed.
-
- Read the README.src file for more information on using the
- conventional source tarball.
-
-
- Note: even with the Unix bundles, e.g. "ssvnc_no_windows" or
- "ssvnc_all", you may need to run the "./build.unix" script in the top
- directory to recompile for your operating system.
-
- Here are the corresponding 1.0.29 development bundles (Please help
- test them):
-
- ssvnc_windows_only-1.0.29.zip
- ssvnc_no_windows-1.0.29.tar.gz
- ssvnc_unix_only-1.0.29.tar.gz
- ssvnc_unix_minimal-1.0.29.tar.gz
-
- ssvnc-1.0.29.tar.gz
- ssvnc-1.0.29.zip
- ssvnc_all-1.0.29.zip
-
- ssvnc-1.0.29.src.tar.gz Conventional Source for SSVNC GUI and Unix
- VNCviewer (0.5MB)
-
-
- For any Unix system, a self-extracting and running file for the
- "ssvnc_unix_minimal" package is here: ssvnc. Save it as filename
- "ssvnc", type "chmod 755 ./ssvnc", and then launch the GUI via typing
- "./ssvnc". Note that this "ssvnc_unix_minimal" mode requires you
- install the "stunnel" and "vncviewer" programs externally (for
- example, install your distros' versions, e.g. on debian: "apt-get
- install stunnel4 xtightvncviewer".) It will work, but many of the
- SSVNC features will be missing.
-
- Previous releases:
- Release 1.0.18 at Sourceforge.net
- Release 1.0.19 at Sourceforge.net
- Release 1.0.20 at Sourceforge.net
- Release 1.0.21 at Sourceforge.net
- Release 1.0.22 at Sourceforge.net
- Release 1.0.23 at Sourceforge.net
- Release 1.0.24 at Sourceforge.net
- Release 1.0.25 at Sourceforge.net
- Release 1.0.26 at Sourceforge.net
- Release 1.0.27 at Sourceforge.net
- Release 1.0.28 at Sourceforge.net
-
-
- Please help test the UltraVNC File Transfer support in the native Unix
- VNC viewer! Let us know how it went.
-
- Current Unix binaries in the archives:
- Linux.i686
- Linux.x86_64
- Linux.ppc64 X (removed)
- Linux.alpha X (removed)
- SunOS.sun4u
- SunOS.sun4m
- SunOS.i86pc
- Darwin.Power.Macintosh
- Darwin.i386
- HP-UX.9000 X (removed)
- FreeBSD.i386 X (removed)
- NetBSD.i386 X (removed)
- OpenBSD.i386 X (removed)
-
- (some of these are out of date, marked with 'X' above, because I no
- longer have access to machines running those OS's. Use the
- "build.unix" script to recompile on your system).
-
- Note: some of the above binaries depend on libssl.so.0.9.7, whereas
- some recent distros only provide libssl.so.0.9.8 by default (for
- compatibility reasons they should install both by default but not all
- do). So you may need to instruct your distro to install the 0.9.7
- library (it is fine to have both runtimes installed simultaneously
- since the libraries have different names). Update: I now try to
- statically link libssl.a for all of the binaries in the archive.
-
- You can also run the included build.unix script to try to
- automatically build the binaries if your OS is not in the above list
- or the included binary does not run properly on your system. Let me
- know how that goes.
- _________________________________________________________________
-
- IMPORTANT: there may be restrictions for you to download, use, or
- redistribute the above because of cryptographic software they contain
- or for other reasons. Please check out your situation and information
- at the following and related sites:
- http://stunnel.mirt.net
- http://www.stunnel.org
- http://www.openssl.org
- http://www.chiark.greenend.org.uk/~sgtatham/putty/
- http://www.tightvnc.com
- http://www.realvnc.com
- http://sourceforge.net/projects/cotvnc/
- _________________________________________________________________
-
- README: Here is the toplevel README from the bundle.
-
-=======================================================================
-http://www.karlrunge.com/x11vnc/x11vnc_opts.html:
-
-
- _________________________________________________________________
-
-x11vnc: a VNC server for real X displays
-
- Here are all of x11vnc command line options:
-% x11vnc -opts (see below for -help long descriptions)
-
-x11vnc: allow VNC connections to real X11 displays. 0.9.13 lastmod: 2010-12-27
-
-x11vnc options:
- -display disp -auth file -N
- -autoport n -rfbport str -6
- -no6 -noipv6 -noipv4
- -reopen -reflect host:N -id windowid
- -sid windowid -appshare -clip WxH+X+Y
- -flashcmap -shiftcmap n -notruecolor
- -advertise_truecolor -visual n -overlay
- -overlay_nocursor -8to24 [opts] -24to32
- -scale fraction -geometry WxH -scale_cursor frac
- -viewonly -shared -once
- -forever -loop -timeout n
- -sleepin n -inetd -tightfilexfer
- -ultrafilexfer -http -http_ssl
- -avahi -mdns -zeroconf
- -connect string -connect_or_exit str -proxy string
- -vncconnect -novncconnect -allow host1[,host2..]
- -localhost -unixsock str -listen6 str
- -nolookup -input string -grabkbd
- -grabptr -ungrabboth -grabalways
- -viewpasswd string -passwdfile filename -showrfbauth filename
- -unixpw [list] -unixpw_nis [list] -unixpw_cmd cmd
- -find -finddpy -listdpy
- -findauth [disp] -create -xdummy
- -xvnc -xvnc_redirect -xdummy_xvfb
- -create_xsrv str -svc -svc_xdummy
- -svc_xvnc -svc_xdummy_xvfb -xdmsvc
- -sshxdmsvc -unixpw_system_greeter -redirect port
- -display WAIT:... -vencrypt mode -anontls mode
- -sslonly -dhparams file -nossl
- -ssl [pem] -ssltimeout n -sslnofail
- -ssldir dir -sslverify path -sslCRL path
- -sslGenCA [dir] -sslGenCert type name -sslEncKey pem
- -sslCertInfo pem -sslDelCert pem -sslScripts
- -stunnel [pem] -stunnel3 [pem] -enc cipher:keyfile
- -https [port] -httpsredir [port] -http_oneport
- -ssh user@host:disp -usepw -storepasswd pass file
- -nopw -accept string -afteraccept string
- -gone string -users list -noshm
- -flipbyteorder -onetile -solid [color]
- -blackout string -xinerama -noxinerama
- -xtrap -xrandr [mode] -rotate string
- -padgeom WxH -o logfile -flag file
- -rmflag file -rc filename -norc
- -env VAR=VALUE -prog /path/to/x11vnc -h, -help
- -?, -opts -V, -version -license
- -dbg -q, -quiet -v, -verbose
- -bg -modtweak -nomodtweak
- -xkb -noxkb -capslock
- -skip_lockkeys -noskip_lockkeys -skip_keycodes string
- -sloppy_keys -skip_dups -noskip_dups
- -add_keysyms -noadd_keysyms -clear_mods
- -clear_keys -clear_all -remap string
- -norepeat -repeat -nofb
- -nobell -nosel -noprimary
- -nosetprimary -noclipboard -nosetclipboard
- -seldir string -cursor [mode] -nocursor
- -cursor_drag -arrow n -noxfixes
- -alphacut n -alphafrac fraction -alpharemove
- -noalphablend -nocursorshape -cursorpos
- -nocursorpos -xwarppointer -noxwarppointer
- -always_inject -buttonmap string -nodragging
- -ncache n -ncache_cr -ncache_no_moveraise
- -ncache_no_dtchange -ncache_no_rootpixmap -ncache_keep_anims
- -ncache_old_wm -ncache_pad n -debug_ncache
- -wireframe [str] -nowireframe -nowireframelocal
- -wirecopyrect mode -nowirecopyrect -debug_wireframe
- -scrollcopyrect mode -noscrollcopyrect -scr_area n
- -scr_skip list -scr_inc list -scr_keys list
- -scr_term list -scr_keyrepeat lo-hi -scr_parms string
- -fixscreen string -debug_scroll -noxrecord
- -grab_buster -nograb_buster -debug_grabs
- -debug_sel -pointer_mode n -input_skip n
- -allinput -input_eagerly -speeds rd,bw,lat
- -wmdt string -debug_pointer -debug_keyboard
- -defer time -wait time -extra_fbur n
- -wait_ui factor -setdefer n -nowait_bog
- -slow_fb time -xrefresh time -nap
- -nonap -sb time -readtimeout n
- -ping n -nofbpm -fbpm
- -nodpms -dpms -forcedpms
- -clientdpms -noserverdpms -noultraext
- -chatwindow -noxdamage -xd_area A
- -xd_mem f -sigpipe string -threads
- -nothreads -fs f -gaps n
- -grow n -fuzz n -debug_tiles
- -snapfb -rawfb string -freqtab file
- -pipeinput cmd -macnodim -macnosleep
- -macnosaver -macnowait -macwheel n
- -macnoswap -macnoresize -maciconanim n
- -macmenu -macuskbd -macnoopengl
- -macnorawfb -gui [gui-opts] -remote command
- -query variable -QD variable -sync
- -query_retries str -remote_prefix str -noremote
- -yesremote -unsafe -safer
- -privremote -nocmds -allowedcmds list
- -deny_all
-
-LibVNCServer options:
--rfbport port TCP port for RFB protocol
--rfbwait time max time in ms to wait for RFB client
--rfbauth passwd-file use authentication on RFB protocol
- (use 'storepasswd' to create a password file)
--rfbversion 3.x Set the version of the RFB we choose to advertise
--permitfiletransfer permit file transfer support
--passwd plain-password use authentication
- (use plain-password as password, USE AT YOUR RISK)
--deferupdate time time in ms to defer updates (default 40)
--deferptrupdate time time in ms to defer pointer updates (default none)
--desktop name VNC desktop name (default "LibVNCServer")
--alwaysshared always treat new clients as shared
--nevershared never treat new clients as shared
--dontdisconnect don't disconnect existing clients when a new non-shared
- connection comes in (refuse new connection instead)
--httpdir dir-path enable http server using dir-path home
--httpport portnum use portnum for http connection
--enablehttpproxy enable http proxy support
--progressive height enable progressive updating for slow links
--listen ipaddr listen for connections only on network interface with
- addr ipaddr. '-listen localhost' and hostname work too.
-
-libvncserver-tight-extension options:
--disablefiletransfer disable file transfer
--ftproot string set ftp root
-
-
-
-
-% x11vnc -help
-
-x11vnc: allow VNC connections to real X11 displays. 0.9.13 lastmod: 2010-12-27
-
-(type "x11vnc -opts" to just list the options.)
-
-Typical usage is:
-
- Run this command in a shell on the remote machine "far-host"
- with X session you wish to view:
-
- x11vnc -display :0
-
- Then run this in another window on the machine you are sitting at:
-
- vncviewer far-host:0
-
-Once x11vnc establishes connections with the X11 server and starts listening
-as a VNC server it will print out a string: PORT=XXXX where XXXX is typically
-5900 (the default VNC server port). One would next run something like
-this on the local machine: "vncviewer hostname:N" where "hostname" is
-the name of the machine running x11vnc and N is XXXX - 5900, i.e. usually
-"vncviewer hostname:0".
-
-By default x11vnc will not allow the screen to be shared and it will exit
-as soon as the client disconnects. See -shared and -forever below to override
-these protections. See the FAQ for details how to tunnel the VNC connection
-through an encrypted channel such as ssh(1). In brief:
-
- ssh -t -L 5900:localhost:5900 far-host 'x11vnc -localhost -display :0'
-
- vncviewer -encodings 'copyrect tight zrle hextile' localhost:0
-
-Also, use of a VNC password (-rfbauth or -passwdfile) is strongly recommended.
-
-For additional info see: http://www.karlrunge.com/x11vnc/
- and http://www.karlrunge.com/x11vnc/faq.html
-
-
-Config file support: if the file $HOME/.x11vncrc exists then each line in
-it is treated as a single command line option. Disable with -norc. For
-each option name, the leading character "-" is not required. E.g. a line
-that is either "forever" or "-forever" may be used and are equivalent.
-Likewise "wait 100" or "-wait 100" are acceptable and equivalent lines.
-The "#" character comments out to the end of the line in the usual way
-(backslash it for a literal). Leading and trailing whitespace is trimmed off.
-Lines may be continued with a "\" as the last character of a line (it
-becomes a space character).
-
-Options:
-
--display disp X11 server display to connect to, usually :0. The X
- server process must be running on same machine and
- support MIT-SHM. Equivalent to setting the DISPLAY
- environment variable to "disp".
-
- See the description below of the "-display WAIT:..."
- extensions, where alias "-find" will find the user's
- display automatically, and "-create" will create a
- Xvfb session if no session is found.
-
--auth file Set the X authority file to be "file", equivalent to
- setting the XAUTHORITY environment variable to "file"
- before startup. Same as -xauth file. See Xsecurity(7),
- xauth(1) man pages for more info.
-
- Use '-auth guess' to have x11vnc use its -findauth
- mechanism (described below) to try to guess the
- XAUTHORITY filename and use it.
-
- XDM/GDM/KDM: if you are running x11vnc as root and want
- to find the XAUTHORITY before anyone has logged into an
- X session yet, use: x11vnc -env FD_XDM=1 -auth guess ...
- (This will also find the XAUTHORITY if a user is already
- logged into the X session.) When running as root,
- FD_XDM=1 will be tried if the initial -auth guess fails.
-
--N If the X display is :N, try to set the VNC display to
- also be :N This just sets the -rfbport option to 5900+N
- The program will exit immediately if that port is not
- available. The -N option only works with normal -display
- usage, e.g. :0 or :8, -N is ignored in the -display
- WAIT:..., -create, -find, -svc, -redirect, etc modes.
-
--autoport n Automatically probe for a free VNC port starting at n.
- The default is to start probing at 5900. Use this to
- stay away from other VNC servers near 5900.
-
--rfbport str The VNC port to listen on (a LibVNCServer option), e.g.
- 5900, 5901, etc. If specified as "-rfbport PROMPT"
- then the x11vnc -gui is used to prompt the user to
- enter the port number.
-
--6 IPv6 listening support. In addition to IPv4, the
- IPv6 address is listened on for incoming connections.
- The same port number as IPv4 is used.
-
- NOTE: This x11vnc binary was compiled to have the
- "-6" IPv6 listening mode ENABLED by default (CPPFLAGS
- -DX11VNC_LISTEN6=1). So to disable IPv6 listening mode
- you MUST supply the "-no6" option (see below.)
-
- The "-6" mode works for both normal connections and
- -ssl encrypted ones. Nearly everything is supported
- for the IPv6 case, but there are a few exceptions.
- See -stunnel for its IPv6 support.
-
- Currently, for absolutely everything to work correctly
- the machine may need to have some IPv4 support, at the
- least for the loopback interface. However, for nearly
- all usage modes no IPv4 support is required. See -nopiv4
-.
-
- If you have trouble compiling or running in IPv6 mode,
- set -DX11VNC_IPV6=0 in CPPFLAGS when configuring to
- disable IPv6 support.
-
--no6 Disable IPv6 listening support (only useful if the
- "-6" mode is compiled in to be the default; see the
- X11VNC_LISTEN6 description above under "-6".)
-
--noipv6 Do not try to use IPv6 for any listening or connecting
- sockets. This includes both the listening service
- port(s) and outgoing connections from -connect,
- -connect_or_exit, or -proxy. Use this if you are having
- problems due to IPv6.
-
--noipv4 Do not try to use IPv4 for any listening or connecting
- sockets. This is mainly for exploring the behavior of
- x11vnc on an IPv6-only system, but may have other uses.
-
--reopen If the X server connection is disconnected, try to
- reopen the X display (up to one time.) This is of use
- for display managers like GDM (KillInitClients option)
- that kill x11vnc just after the user logs into the
- X session. Note: the reopened state may be unstable.
- Set X11VNC_REOPEN_DISPLAY=n to reopen n times and
- set X11VNC_REOPEN_SLEEP_MAX to the number of seconds,
- default 10, to keep trying to reopen the display (once
- per second.)
-
- Update: as of 0.9.9, x11vnc tries to automatically avoid
- being killed by the display manager by delaying creating
- windows or using XFIXES. So you shouldn't need to use
- KillInitClients=false as long as you log in quickly
- enough (within 45 seconds of connecting.) You can
- disable this by setting X11VNC_AVOID_WINDOWS=never.
- You can also set it to the number of seconds to delay.
-
--reflect host:N Instead of connecting to and polling an X display,
- connect to the remote VNC server host:N and be a
- reflector/repeater for it. This is useful for trying
- to manage the case of many simultaneous VNC viewers
- (e.g. classroom broadcasting) where, e.g. you put
- a repeater on each network switch, etc, to improve
- performance by distributing the load and network
- traffic. Implies -shared (use -noshared as a later
- option to disable). See the discussion below under
- -rawfb vnc:host:N for more details.
-
--id windowid Show the X window corresponding to "windowid" not
- the entire display. New windows like popup menus,
- transient toplevels, etc, may not be seen or may be
- clipped. Disabling SaveUnders or BackingStore in the
- X server may help show them. x11vnc may crash if the
- window is initially partially obscured, changes size,
- is iconified, etc. Some steps are taken to avoid this
- and the -xrandr mechanism is used to track resizes. Use
- xwininfo(1) to get the window id, or use "-id pick"
- to have x11vnc run xwininfo(1) for you and extract
- the id. The -id option is useful for exporting very
- simple applications (e.g. the current view on a webcam).
--sid windowid As -id, but instead of using the window directly it
- shifts a root view to it: this shows SaveUnders menus,
- etc, although they will be clipped if they extend beyond
- the window.
-
--appshare Simple application sharing based on the -id/-sid
- mechanism. Every new toplevel window that the
- application creates induces a new viewer window via
- a reverse connection. The -id/-sid and -connect
- options are required. Run 'x11vnc -appshare -help'
- for more info.
-
--clip WxH+X+Y Only show the sub-region of the full display that
- corresponds to the rectangle geometry with size WxH and
- offset +X+Y. The VNC display has size WxH (i.e. smaller
- than the full display). This also works for -id/-sid
- mode where the offset is relative to the upper left
- corner of the selected window. An example use of this
- option would be to split a large (e.g. Xinerama) display
- into two parts to be accessed via separate viewers by
- running a separate x11vnc on each part.
-
- Use '-clip xinerama0' to clip to the first xinerama
- sub-screen (if xinerama is active). xinerama1 for the
- 2nd sub-screen, etc. This way you don't need to figure
- out the WxH+X+Y of the desired xinerama sub-screen.
- screens are sorted in increasing distance from the
- (0,0) origin (I.e. not the Xserver's order).
-
--flashcmap In 8bpp indexed color, let the installed colormap flash
- as the pointer moves from window to window (slow).
- Also try the -8to24 option to avoid flash altogether.
--shiftcmap n Rare problem, but some 8bpp displays use less than 256
- colorcells (e.g. 16-color grayscale, perhaps the other
- bits are used for double buffering) *and* also need to
- shift the pixels values away from 0, .., ncells. "n"
- indicates the shift to be applied to the pixel values.
- To see the pixel values set DEBUG_CMAP=1 to print out
- a colormap histogram. Example: -shiftcmap 240
--notruecolor For 8bpp displays, force indexed color (i.e. a colormap)
- even if it looks like 8bpp TrueColor (rare problem).
--advertise_truecolor If the X11 display is indexed color, lie to clients
- when they first connect by telling them it is truecolor.
- To workaround RealVNC: inPF has colourMap but not 8bpp
- Use '-advertise_truecolor reset' to reset client fb too.
-
--visual n This option probably does not do what you think.
- It simply *forces* the visual used for the framebuffer;
- this may be a bad thing... (e.g. messes up colors or
- cause a crash). It is useful for testing and for some
- workarounds. n may be a decimal number, or 0x hex.
- Run xdpyinfo(1) for the values. One may also use
- "TrueColor", etc. see <X11/X.h> for a list. If the
- string ends in ":m" then for better or for worse
- the visual depth is forced to be m. You may want to
- use -noshm when using this option (so XGetImage may
- automatically translate the pixel data).
-
--overlay Handle multiple depth visuals on one screen, e.g. 8+24
- and 24+8 overlay visuals (the 32 bits per pixel are
- packed with 8 for PseudoColor and 24 for TrueColor).
-
- Currently -overlay only works on Solaris via
- XReadScreen(3X11) and IRIX using XReadDisplay(3).
- On Solaris there is a problem with image "bleeding"
- around transient popup menus (but not for the menu
- itself): a workaround is to disable SaveUnders
- by passing the "-su" argument to Xsun (in
- /etc/dt/config/Xservers).
-
- Use -overlay as a workaround for situations like these:
- Some legacy applications require the default visual to
- be 8bpp (8+24), or they will use 8bpp PseudoColor even
- when the default visual is depth 24 TrueColor (24+8).
- In these cases colors in some windows will be incorrect
- in x11vnc unless -overlay is used. Another use of
- -overlay is to enable showing the exact mouse cursor
- shape (details below).
-
- Under -overlay, performance will be somewhat slower
- due to the extra image transformations required.
- For optimal performance do not use -overlay, but rather
- configure the X server so that the default visual is
- depth 24 TrueColor and try to have all apps use that
- visual (e.g. some apps have -use24 or -visual options).
--overlay_nocursor Sets -overlay, but does not try to draw the exact mouse
- cursor shape using the overlay mechanism.
-
--8to24 [opts] Try this option if -overlay is not supported on your
- OS, and you have a legacy 8bpp app that you want to
- view on a multi-depth display with default depth 24
- (and is 32 bpp) OR have a default depth 8 display with
- depth 24 overlay windows for some apps. This option
- may not work on all X servers and hardware (tested
- on XFree86/Xorg mga driver and Xsun). The "opts"
- string is not required and is described below.
-
- This mode enables a hack where x11vnc monitors windows
- within 3 levels from the root window. If it finds
- any that are 8bpp it extracts the indexed color
- pixel values using XGetImage() and then applies a
- transformation using the colormap(s) to create TrueColor
- RGB values that it in turn inserts into bits 1-24 of
- the framebuffer. This creates a depth 24 "view"
- of the display that is then exported via VNC.
-
- Conversely, for default depth 8 displays, the depth
- 24 regions are read by XGetImage() and everything is
- transformed and inserted into a depth 24 TrueColor
- framebuffer.
-
- Note that even if there are *no* depth 24 visuals or
- windows (i.e. pure 8bpp), this mode is potentially
- an improvement over -flashcmap because it avoids the
- flashing and shows each window in the correct color.
-
- This method works OK, but may still have bugs and it
- does hog resources. If there are multiple 8bpp windows
- using different colormaps, one may have to iconify all
- but one for the colors to be correct.
-
- There may be painting errors for clipping and switching
- between windows of depths 8 and 24. Heuristics are
- applied to try to minimize the painting errors. One can
- also press 3 Alt_L's in a row to refresh the screen
- if the error does not repair itself. Also the option
- -fixscreen 8=3.0 or -fixscreen V=3.0 may be used to
- periodically refresh the screen at the cost of bandwidth
- (every 3 sec for this example).
-
- The [opts] string can contain the following settings.
- Multiple settings are separated by commas.
-
- For for some X servers with default depth 24 a
- speedup may be achieved via the option "nogetimage".
- This enables a scheme were XGetImage() is not used
- to retrieve the 8bpp data. Instead, it assumes that
- the 8bpp data is in bits 25-32 of the 32bit X pixels.
- There is no requirement that the X server should put
- the data there for our poll requests, but some do and
- so the extra steps to retrieve it can be skipped.
- Tested with mga driver with XFree86/Xorg. For the
- default depth 8 case this option is ignored.
-
- To adjust how often XGetImage() is used to poll the
- non-default visual regions for changes, use the option
- "poll=t" where "t" is a floating point time.
- (default: 0.05)
-
- Setting the option "level2" will limit the search
- for non-default visual windows to two levels from the
- root window. Do this on slow machines where you know
- the window manager only imposes one extra window between
- the app window and the root window.
-
- Also for very slow machines use "cachewin=t"
- where t is a floating point amount of time to cache
- XGetWindowAttributes results. E.g. cachewin=5.0.
- This may lead to the windows being unnoticed for this
- amount of time when deiconifying, painting errors, etc.
-
- While testing on a very old SS20 these options gave
- tolerable response: -8to24 poll=0.2,cachewin=5.0. For
- this machine -overlay is supported and gives better
- response.
-
- Debugging for this mode can be enabled by setting
- "dbg=1", "dbg=2", or "dbg=3".
-
--24to32 Very rare problem: if the framebuffer (X display
- or -rawfb) is 24bpp instead of the usual 32bpp, then
- dynamically transform the pixels to 32bpp. This will be
- slower, but can be used to work around problems where
- VNC viewers cannot handle 24bpp (e.g. "main: setPF:
- not 8, 16 or 32 bpp?"). See the FAQ for more info.
-
- In the case of -rawfb mode, the pixels are directly
- modified by inserting a 0 byte to pad them out to 32bpp.
- For X displays, a kludge is done that is equivalent to
- "-noshm -visual TrueColor:32". (If better performance
- is needed for the latter, feel free to ask).
-
--scale fraction Scale the framebuffer by factor "fraction". Values
- less than 1 shrink the fb, larger ones expand it. Note:
- the image may not be sharp and response may be slower.
- If "fraction" contains a decimal point "." it
- is taken as a floating point number, alternatively
- the notation "m/n" may be used to denote fractions
- exactly, e.g. -scale 2/3
-
- To scale asymmetrically in the horizontal and vertical
- directions, specify a WxH geometry to stretch to:
- e.g. '-scale 1024x768', or also '-scale 0.9x0.75'
-
- Scaling Options: can be added after "fraction" via
- ":", to supply multiple ":" options use commas.
- If you just want a quick, rough scaling without
- blending, append ":nb" to "fraction" (e.g. -scale
- 1/3:nb). No blending is the default for 8bpp indexed
- color, to force blending for this case use ":fb".
-
- To disable -scrollcopyrect and -wirecopyrect under
- -scale use ":nocr". If you need to to enable them use
- ":cr" or specify them explicitly on the command line.
- If a slow link is detected, ":nocr" may be applied
- automatically. Default: :cr
-
- More esoteric options: for compatibility with vncviewers
- the scaled width is adjusted to be a multiple of 4:
- to disable this use ":n4". ":in" use interpolation
- scheme even when shrinking, ":pad" pad scaled width
- and height to be multiples of scaling denominator
- (e.g. 3 for 2/3).
-
--geometry WxH Same as -scale WxH
-
--scale_cursor frac By default if -scale is supplied the cursor shape is
- scaled by the same factor. Depending on your usage,
- you may want to scale the cursor independently of the
- screen or not at all. If you specify -scale_cursor
- the cursor will be scaled by that factor. When using
- -scale mode to keep the cursor at its "natural" size
- use "-scale_cursor 1". Most of the ":" scaling
- options apply here as well.
-
--viewonly All VNC clients can only watch (default off).
--shared VNC display is shared, i.e. more than one viewer can
- connect at the same time (default off).
--once Exit after the first successfully connected viewer
- disconnects, opposite of -forever. This is the Default.
--forever Keep listening for more connections rather than exiting
- as soon as the first client(s) disconnect. Same as -many
-
- To get the standard non-shared VNC behavior where when
- a new VNC client connects the existing VNC client is
- dropped use: -nevershared -forever This method can
- also be used to guard against hung TCP connections that
- do not go away.
-
--loop Create an outer loop restarting the x11vnc process
- whenever it terminates. -bg and -inetd are ignored
- in this mode (however see -loopbg below).
-
- Useful for continuing even if the X server terminates
- and restarts (at that moment the process will need
- permission to reconnect to the new X server of course).
-
- Use, e.g., -loop100 to sleep 100 millisecs between
- restarts, etc. Default is 2000ms (i.e. 2 secs) Use,
- e.g. -loop300,5 to sleep 300 ms and only loop 5 times.
-
- If -loopbg (plus any numbers) is specified instead,
- the "-bg" option is implied and the mode approximates
- inetd(8) usage to some degree. In this case when
- it goes into the background any listening sockets
- (i.e. ports 5900, 5800) are closed, so the next one
- in the loop can use them. This mode will only be of
- use if a VNC client (the only client for that process)
- is already connected before the process goes into the
- background, for example, usage of -display WAIT:..,
- -svc, and -connect can make use of this "poor man's"
- inetd mode. The default wait time is 500ms in this
- mode. This usage could use useful: -svc -bg -loopbg
-
--timeout n Exit unless a client connects within the first n seconds
- after startup.
-
- If there have been no connection attempts after n
- seconds x11vnc exits immediately. If a client is
- trying to connect but has not progressed to the normal
- operating state, x11vnc gives it a few more seconds
- to finish and exits if it does not make it to the
- normal state.
-
- For reverse connections via -connect or -connect_or_exit
- a timeout of n seconds will be set for all reverse
- connects. If the connect timeout alarm goes off,
- x11vnc will exit immediately.
-
--sleepin n At startup sleep n seconds before proceeding (e.g. to
- allow redirs and listening clients to start up)
-
- If a range is given: '-sleepin min-max', a random value
- between min and max is slept. E.g. '-sleepin 0-20' and
- '-sleepin 10-30'. Floats are allowed too.
-
--inetd Launched by inetd(8): stdio instead of listening socket.
- Note: if you are not redirecting stderr to a log file
- (via shell 2> or -o option) you MUST also specify the -q
- option, otherwise the stderr goes to the viewer which
- will cause it to abort. Specifying both -inetd and -q
- and no -o will automatically close the stderr.
-
--tightfilexfer Enable the TightVNC file transfer extension. Note that
- that when the -viewonly option is supplied all file
- transfers are disabled. Also clients that log in
- viewonly cannot transfer files. However, if the remote
- control mechanism is used to change the global or
- per-client viewonly state the filetransfer permissions
- will NOT change.
-
- IMPORTANT: please understand if -tightfilexfer is
- specified and you run x11vnc as root for, say, inetd
- or display manager (gdm, kdm, ...) access and you do
- not have it switch users via the -users option, then
- VNC Viewers that connect are able to do filetransfer
- reads and writes as *root*.
-
- Also, tightfilexfer is disabled in -unixpw mode.
-
--ultrafilexfer Note: to enable UltraVNC filetransfer and to get it to
- work you probably need to supply these LibVNCServer
- options: "-rfbversion 3.6 -permitfiletransfer"
- "-ultrafilexfer" is an alias for this combination.
-
- IMPORTANT: please understand if -ultrafilexfer is
- specified and you run x11vnc as root for, say, inetd
- or display manager (gdm, kdm, ...) access and you do
- not have it switch users via the -users option, then
- VNC Viewers that connect are able to do filetransfer
- reads and writes as *root*.
-
- Note that sadly you cannot do both -tightfilexfer and
- -ultrafilexfer at the same time because the latter
- requires setting the version to 3.6 and tightvnc will
- not do filetransfer when it sees that version number.
-
--http Instead of using -httpdir (see below) to specify
- where the Java vncviewer applet is, have x11vnc try
- to *guess* where the directory is by looking relative
- to the program location and in standard locations
- (/usr/local/share/x11vnc/classes, etc). Under -ssl or
- -stunnel the ssl classes subdirectory is sought.
--http_ssl As -http, but force lookup for ssl classes subdir.
-
- Note that for HTTPS, single-port Java applet delivery
- you can set X11VNC_HTTPS_DOWNLOAD_WAIT_TIME to the
- max number of seconds to wait for the applet download
- to finish. The default is 15.
-
--avahi Use the Avahi/mDNS ZeroConf protocol to advertise
- this VNC server to the local network. (Related terms:
- Rendezvous, Bonjour). Depending on your setup, you
- may need to start avahi-daemon and open udp port 5353
- in your firewall.
-
- You can set X11VNC_AVAHI_NAME, X11VNC_AVAHI_HOST,
- and/or X11VNC_AVAHI_PORT environment variables
- to override the default values. For example:
- -env X11VNC_AVAHI_NAME=wally
-
- If the avahi API cannot be found at build time, a helper
- program like avahi-publish(1) or dns-sd(1) will be tried
-
--mdns Same as -avahi.
--zeroconf Same as -avahi.
-
--connect string For use with "vncviewer -listen" reverse connections.
- If "string" has the form "host" or "host:port"
- the connection is made once at startup.
-
- Use commas for a list of host's and host:port's.
- E.g. -connect host1,host2 or host1:0,host2:5678.
- Note that to reverse connect to multiple hosts at the
- same time you will likely need to also supply: -shared
-
- Note that unlike most vnc servers, x11vnc will require a
- password for reverse as well as for forward connections.
- (provided password auth has been enabled, -rfbauth, etc)
- If you do not want to require a password for reverse
- connections set X11VNC_REVERSE_CONNECTION_NO_AUTH=1 in
- your environment before starting x11vnc.
-
- If "string" contains "/" it is instead interpreted
- as a file to periodically check for new hosts.
- The first line is read and then the file is truncated.
- Be careful about the location of this file if x11vnc
- is running as root (e.g. via gdm(1), etc).
-
-
- Repeater mode: Some services provide an intermediate
- "vnc repeater": http://www.uvnc.com/addons/repeater.html
- (and also http://koti.mbnet.fi/jtko/ for linux port)
- that acts as a proxy/gateway. Modes like these require
- an initial string to be sent for the reverse connection
- before the VNC protocol is started. Here are the ways
- to do this:
-
- -connect pre=some_string+host:port
- -connect pre128=some_string+host:port
- -connect repeater=ID:1234+host:port
- -connect repeater=23.45.67.89::5501+host:port
-
- SSVNC notation is also supported:
-
- -connect repeater://host:port+ID:1234
-
- As with normal -connect usage, if the repeater port is
- not supplied 5500 is assumed.
-
- The basic idea is between the special tag, e.g. "pre="
- and "+" is the pre-string to be sent. Note that in
- this case host:port is the repeater server, NOT the
- vnc viewer. Somehow the pre-string tells the repeater
- server how to find the vnc viewer and connect you to it.
-
- In the case pre=some_string+host:port, "some_string"
- is simply sent. In the case preNNN=some_string+host:port
- "some_string" is sent in a null padded buffer of
- length NNN. repeater= is the same as pre250=, this is
- the ultravnc repeater buffer size.
-
- Strings like "\n" and "\r", etc. are expanded to
- newline and carriage return. "\c" is expanded to
- "," since the connect string is comma separated.
-
- See also the -proxy option below for additional ways
- to plumb reverse connections.
-
- Reverse SSL: using -connect in -ssl mode makes x11vnc
- act as an SSL client (initiates SSL connection) rather
- than an SSL server. The idea is x11vnc might be
- connecting to stunnel on the viewer side with the
- viewer in listening mode. If you do not want this
- behavior, use -env X11VNC_DISABLE_SSL_CLIENT_MODE=1.
- With this the viewer side can act as the SSL client
- as it normally does for forward connections.
-
- Reverse SSL Repeater mode: This will work, but note
- that if the VNC Client does any sort of a 'Fetch Cert'
- action before connecting, then the Repeater will
- likely drop the connection and both sides will need
- to restart. Consider the use of -connect_or_exit
- and -loop300,2 to have x11vnc reconnect once to the
- repeater after the fetch. You will probably also want
- to supply -sslonly to avoid x11vnc thinking the delay
- in response means the connection is VeNCrypt. The env
- var X11VNC_DISABLE_SSL_CLIENT_MODE=1 discussed above
- may also be useful (i.e. the viewer can do a forward
- connection as it normally does.)
-
- IPv6: as of x11vnc 0.9.10 the -connect option should
- connect to IPv6 hosts properly. If there are problems
- you can disable IPv6 by setting -DX11VNC_IPV6=0
- in CPPFLAGS when configuring. If there problems
- connecting to IPv6 hosts consider a relay like the
- included inet6to4 script or the -proxy option.
-
--connect_or_exit str As with -connect, except if none of the reverse
- connections succeed, then x11vnc shuts down immediately
-
- An easier to type alias for this option is '-coe'
-
- By the way, if you do not want x11vnc to listen on
- ANY interface use -rfbport 0 which is handy for the
- -connect_or_exit mode.
-
--proxy string Use proxy in string (e.g. host:port) as a proxy for
- making reverse connections (-connect or -connect_or_exit
- options).
-
- Web proxies are supported, but note by default most of
- them only support destination connections to ports 443
- or 563, so this might not be very useful (the viewer
- would need to listen on that port or the router would
- have to do a port redirection).
-
- A web proxy may be specified by either "host:port"
- or "http://host:port" (the port is required even if
- it is the common choices 80 or 8080)
-
- SOCKS4, SOCKS4a, and SOCKS5 are also supported.
- SOCKS proxies normally do not have restrictions on the
- destination port number.
-
- Use a format like this: socks://host:port or
- socks5://host:port. Note that ssh -D does not support
- SOCKS4a, so use socks5://. For socks:// SOCKS4 is used
- on a numerical IP and "localhost", otherwise SOCKS4a
- is used (and so the proxy tries to do the DNS lookup).
-
- An experimental mode is "-proxy http://host:port/..."
- Note the "/" after the port that distinguishes it from
- a normal web proxy. The port must be supplied even if
- it is the default 80. For this mode a GET is done to
- the supplied URL with the string host=H&port=P appended.
- H and P will be the -connect reverse connect host
- and port. Use the string "__END__" to disable the
- appending. The basic idea here is that maybe some cgi
- script provides the actual viewer hookup and tunnelling.
- How to actually achieve this within cgi, php, etc. is
- not clear... A custom web server or apache module
- would be straight-forward.
-
- Another experimental mode is "-proxy ssh://user@host"
- in which case a SSH tunnel is used for the proxying.
- "user@" is not needed unless your unix username is
- different on "host". For a non-standard SSH port
- use ssh://user@host:port. If proxies are chained (see
- next paragraph) then the ssh one must be the first one.
- If ssh-agent is not active, then the ssh password needs
- to be entered in the terminal where x11vnc is running.
- Examples:
-
- -connect localhost:0 -proxy ssh://me@friends-pc:2222
-
- -connect snoopy:0 -proxy ssh://ssh.company.com
-
- Multiple proxies may be chained together in case one
- needs to ricochet off of a number of hosts to finally
- reach the VNC viewer. Up to 3 may be chained, separate
- them by commas in the order they are to be connected to.
- E.g.: http://host1:port1,socks5://host2:port2 or three
- like: first,second,third
-
- IPv6: as of x11vnc 0.9.10 the -proxy option should
- connect to IPv6 hosts properly. If there are problems
- you can disable IPv6 by setting -DX11VNC_IPV6=0
- in CPPFLAGS when configuring. If there problems
- connecting to IPv6 hosts consider a relay like the
- included inet6to4 script.
-
--vncconnect Monitor the VNC_CONNECT X property set by the standard
--novncconnect VNC program vncconnect(1). When the property is
- set to "host" or "host:port" establish a reverse
- connection. Using xprop(1) instead of vncconnect may
- work (see the FAQ). The -remote control mechanism uses
- X11VNC_REMOTE channel, and this option disables/enables
- it as well. Default: -vncconnect
-
- To use different names for these X11 properties (e.g. to
- have separate communication channels for multiple
- x11vnc's on the same display) set the VNC_CONNECT or
- X11VNC_REMOTE env. vars. to the string you want, for
- example: -env X11VNC_REMOTE=X11VNC_REMOTE_12345
- Both sides of the channel must use the same unique name.
- The same can be done for the internal X11VNC_TICKER
- property (heartbeat and timestamp) if desired.
-
--allow host1[,host2..] Only allow client connections from hosts matching
- the comma separated list of hostnames or IP addresses.
- Can also be a numerical IP prefix, e.g. "192.168.100."
- to match a simple subnet, for more control build
- LibVNCServer with libwrap support (See the FAQ). If the
- list contains a "/" it instead is a interpreted
- as a file containing addresses or prefixes that is
- re-read each time a new client connects. Lines can be
- commented out with the "#" character in the usual way.
-
- -allow applies in -ssl mode, but not in -stunnel mode.
-
- IPv6: as of x11vnc 0.9.10 a host can be specified
- in IPv6 numerical format, e.g. 2001:4860:b009::93.
-
--localhost Basically the same as "-allow 127.0.0.1".
-
- Note: if you want to restrict which network interface
- x11vnc listens on, see the -listen option below.
- E.g. "-listen localhost" or "-listen 192.168.3.21".
- As a special case, the option "-localhost" implies
- "-listen localhost".
-
- A rare case, but for non-localhost -listen usage, if
- you use the remote control mechanism (-R) to change
- the -listen interface you may need to manually adjust
- the -allow list (and vice versa) to avoid situations
- where no connections (or too many) are allowed.
-
- If you do not want x11vnc to listen on ANY interface
- (evidently you are using -connect or -connect_or_exit,
- or plan to use remote control: -R connect:host), use
- -rfbport 0
-
- IPv6: if IPv6 is supported, this option automatically
- implies the IPv6 loopback address '::1' as well.
-
--unixsock str Listen on the unix socket (AF_UNIX) 'str'
- for connections. This mode is for either local
- connections or a tunnel endpoint where one wants the
- file permission of the unix socket file to determine
- what can connect to it. (This currently requires an
- edit to libvnserver/rfbserver.c: comment out lines 310
- and 311, 'close(sock)' and 'return NULL' in rfbserver.c
- after the setsockopt() call.) Note that to disable all
- tcp listening ports specify '-rfbport 0' and should be
- useful with this mode. Example:
- mkdir ~/s; chmod 700 ~/s;
- x11vnc -unixsock ~/s/mysock -rfbport 0 ...
- The SSVNC unix vncviewer can connect to unix sockets.
-
--listen6 str When in IPv6 listen mode "-6", listen only on the
- network interface with address "str". It also works
- for link scope addresses (fe80::219:dbff:fee5:3f92%eth0)
- and IPv6 hostname strings (e.g. ipv6.google.com.)
- Use LibVNCServer -listen option for the IPv4 interface.
-
--nolookup Do not use gethostbyname() or gethostbyaddr() to look up
- host names or IP numbers. Use this if name resolution
- is incorrectly set up and leads to long pauses as name
- lookups time out, etc.
-
--input string Fine tuning of allowed user input. If "string" does
- not contain a comma "," the tuning applies only to
- normal clients. Otherwise the part before "," is
- for normal clients and the part after for view-only
- clients. "K" is for Keystroke input, "M" for
- Mouse-motion input, "B" for Button-click input, "C"
- is for Clipboard input, and "F" is for File transfer
- (ultravnc only). Their presence in the string enables
- that type of input. E.g. "-input M" means normal
- users can only move the mouse and "-input KMBCF,M"
- lets normal users do anything and enables view-only
- users to move the mouse. This option is ignored when
- a global -viewonly is in effect (all input is discarded
- in that case).
-
--grabkbd When VNC viewers are connected, attempt to the grab
- the keyboard so a (non-malicious) user sitting at the
- physical display is not able to enter keystrokes.
- This method uses XGrabKeyboard(3X11) and so it is
- not secure and does not rule out the person at the
- physical display injecting keystrokes by flooding the
- server with them, grabbing the keyboard himself, etc.
- Some degree of cooperation from the person at the
- display is assumed. This is intended for remote
- help-desk or educational usage modes.
-
- Note: on some recent (12/2010) X servers and/or
- desktops, -grabkbd no longer works: it prevents the
- window manager from resizing windows and similar things.
- Try -ungrabboth below (might not work.)
-
--grabptr As -grabkbd, but for the mouse pointer using
- XGrabPointer(3X11). Unfortunately due to the way the X
- server works, the mouse can still be moved around by the
- user at the physical display, but he will not be able to
- change window focus with it. Also some window managers
- that call XGrabServer(3X11) for resizes, etc, will
- act on the local user's input. Again, some degree of
- cooperation from the person at the display is assumed.
-
--ungrabboth Whenever there is any input (either keyboard or
- pointer), ungrab *both* the keyboard and the pointer
- while injecting the synthetic input. This is to allow
- window managers, etc. a chance to grab.
-
--grabalways Apply both -grabkbd and -grabptr even when no VNC
- viewers are connected. If you only want one of them,
- use the -R remote control to turn the other back on,
- e.g. -R nograbptr.
-
--viewpasswd string Supply a 2nd password for view-only logins. The -passwd
- (full-access) password must also be supplied.
-
--passwdfile filename Specify the LibVNCServer password via the first line
- of the file "filename" (instead of via -passwd on
- the command line where others might see it via ps(1)).
-
- See the descriptions below for how to supply multiple
- passwords, view-only passwords, to specify external
- programs for the authentication, and other features.
-
- If the filename is prefixed with "rm:" it will be
- removed after being read. Perhaps this is useful in
- limiting the readability of the file. In general, the
- password file should not be readable by untrusted users
- (BTW: neither should the VNC -rfbauth file: it is NOT
- encrypted, only obscured with a fixed key).
-
- If the filename is prefixed with "read:" it will
- periodically be checked for changes and reread. It is
- guaranteed to be reread just when a new client connects
- so that the latest passwords will be used.
-
- If "filename" is prefixed with "cmd:" then the
- string after the ":" is run as an external command:
- the output of the command will be interpreted as if it
- were read from a password file (see below). If the
- command does not exit with 0, then x11vnc terminates
- immediately. To specify more than 1000 passwords this
- way set X11VNC_MAX_PASSWDS before starting x11vnc.
- The environment variables are set as in -accept.
-
- Note that due to the VNC protocol only the first 8
- characters of a password are used (DES key).
-
- If "filename" is prefixed with "custom:" then a
- custom password checker is supplied as an external
- command following the ":". The command will be run
- when a client authenticates. If the command exits with
- 0 the client is accepted, otherwise it is rejected.
- The environment variables are set as in -accept.
-
- The standard input to the custom command will be a
- decimal digit "len" followed by a newline. "len"
- specifies the challenge size and is usually 16 (the
- VNC spec). Then follows len bytes which is the random
- challenge string that was sent to the client. This is
- then followed by len more bytes holding the client's
- response (i.e. the challenge string encrypted via DES
- with the user password in the standard situation).
-
- The "custom:" scheme can be useful to implement
- dynamic passwords or to implement methods where longer
- passwords and/or different encryption algorithms
- are used. The latter will require customizing the VNC
- client as well. One could create an MD5SUM based scheme
- for example.
-
- File format for -passwdfile:
-
- If multiple non-blank lines exist in the file they are
- all taken as valid passwords. Blank lines are ignored.
- Password lines may be "commented out" (ignored) if
- they begin with the character "#" or the line contains
- the string "__SKIP__". Lines may be annotated by use
- of the "__COMM__" string: from it to the end of the
- line is ignored. An empty password may be specified
- via the "__EMPTY__" string on a line by itself (note
- your viewer might not accept empty passwords).
-
- If the string "__BEGIN_VIEWONLY__" appears on a
- line by itself, the remaining passwords are used for
- viewonly access. For compatibility, as a special case
- if the file contains only two password lines the 2nd
- one is automatically taken as the viewonly password.
- Otherwise the "__BEGIN_VIEWONLY__" token must be
- used to have viewonly passwords. (tip: make the 3rd
- and last line be "__BEGIN_VIEWONLY__" to have 2
- full-access passwords)
-
--showrfbauth filename Print to the screen the obscured VNC password kept in
- the rfbauth file "filename" and then exit.
-
--unixpw [list] Use Unix username and password authentication. x11vnc
- will use the su(1) program to verify the user's
- password. [list] is an optional comma separated list
- of allowed Unix usernames. If the [list] string begins
- with the character "!" then the entire list is taken
- as an exclude list. See below for per-user options
- that can be applied.
-
- A familiar "login:" and "Password:" dialog is
- presented to the user on a black screen inside the
- vncviewer. The connection is dropped if the user fails
- to supply the correct password in 3 tries or does not
- send one before a 45 second timeout. Existing clients
- are view-only during this period.
-
- If the first character received is "Escape" then the
- unix username will not be displayed after "login:"
- as it is typed. This could be of use for VNC viewers
- that automatically type the username and password.
-
- Since the detailed behavior of su(1) can vary from
- OS to OS and for local configurations, test the mode
- before deployment to make sure it is working properly.
- x11vnc will attempt to be conservative and reject a
- login if anything abnormal occurs.
-
- One case to note: FreeBSD and the other BSD's by
- default it is impossible for the user running x11vnc to
- validate his *own* password via su(1) (commenting out
- the pam_self.so entry in /etc/pam.d/su eliminates this
- behavior). So the x11vnc login will always *FAIL* for
- this case (even when the correct password is supplied).
-
- A possible workaround for this on *BSD would be to
- start x11vnc as root with the "-users +nobody" option
- to immediately switch to user nobody where the su'ing
- will proceed normally.
-
- Another source of potential problems are PAM modules
- that prompt for extra info, e.g. password aging modules.
- These logins will fail as well even when the correct
- password is supplied.
-
- **IMPORTANT**: to prevent the Unix password being sent
- in *clear text* over the network, one of two schemes
- will be enforced: 1) the -ssl builtin SSL mode, or 2)
- require both -localhost and -stunnel be enabled.
-
- Method 1) ensures the traffic is encrypted between
- viewer and server. A PEM file will be required, see the
- discussion under -ssl below (under some circumstances
- a temporary one can be automatically generated).
-
- Method 2) requires the viewer connection to appear
- to come from the same machine x11vnc is running on
- (e.g. from a ssh -L port redirection). And that the
- -stunnel SSL mode be used for encryption over the
- network. (see the description of -stunnel below).
-
- Note: as a convenience, if you ssh(1) in and start
- x11vnc it will check if the environment variable
- SSH_CONNECTION is set and appears reasonable. If it
- does, then the -ssl or -stunnel requirement will be
- dropped since it is assumed you are using ssh for the
- encrypted tunnelling. -localhost is still enforced.
- Use -ssl or -stunnel to force SSL usage even if
- SSH_CONNECTION is set.
-
- To override the above restrictions you can set
- environment variables before starting x11vnc:
-
- Set UNIXPW_DISABLE_SSL=1 to disable requiring either
- -ssl or -stunnel (as under SSH_CONNECTION.) Evidently
- you will be using a different method to encrypt the
- data between the vncviewer and x11vnc: perhaps ssh(1)
- or an IPSEC VPN. -localhost is still enforced (however,
- see the next paragraph.)
-
- Set UNIXPW_DISABLE_LOCALHOST=1 to disable the -localhost
- requirement in -unixpw modes. One should never do this
- (i.e. allow the Unix passwords to be sniffed on the
- network.) This also disables the localhost requirement
- for reverse connections (see below.)
-
- Note that use of -localhost with ssh(1) (and no -unixpw)
- is roughly the same as requiring a Unix user login
- (since a Unix password or the user's public key
- authentication is used by sshd on the machine where
- x11vnc runs and only local connections from that machine
- are accepted).
-
- Regarding reverse connections (e.g. -R connect:host
- and -connect host), when the -localhost constraint is
- in effect then reverse connections can only be used
- to connect to the same machine x11vnc is running on
- (default port 5500). Please use a ssh or stunnel port
- redirection to the viewer machine to tunnel the reverse
- connection over an encrypted channel.
-
- In -inetd mode the Method 1) will be enforced (not
- Method 2). With -ssl in effect reverse connections
- are disabled. If you override this via env. var, be
- sure to also use encryption from the viewer to inetd.
- Tip: you can also have your own stunnel spawn x11vnc
- in -inetd mode (thereby bypassing inetd). See the FAQ
- for details.
-
- The user names in the comma separated [list] may have
- per-user options after a ":", e.g. "fred:opts"
- where "opts" is a "+" separated list of
- "viewonly", "fullaccess", "input=XXXX", or
- "deny", e.g. "karl,wally:viewonly,boss:input=M".
- For "input=" it is the K,M,B,C described under -input.
-
- If an item in the list is "*" that means those
- options apply to all users. It ALSO implies all users
- are allowed to log in after supplying a valid password.
- Use "deny" to explicitly deny some users if you use
- "*" to set a global option. If [list] begins with the
- "!" character then "*" is ignored for checking if
- the user is allowed, but the option values associated
- with it do apply as normal.
-
- There are also some utilities for checking passwords
- if [list] starts with the "%" character. See the
- quick_pw() function for more details. Description:
- "%-" or "%stdin" means read one line from stdin.
- "%env" means it is in $UNIXPW env var. A leading
- "%/" or "%." means read the first line from the
- filename that follows after the % character. % by
- itself means prompt for the username and password.
- Otherwise: %user:pass E.g. -unixpw %fred:swordfish
- For the other cases user:pass is read from the indicated
- source. If the password is correct 'Y user' is printed
- and the program exit code is 0. If the password is
- incorrect it prints 'N user' and the exit code is 1.
- If there is some other error the exit code is 2.
- This feature enables x11vnc to be a general unix user
- password checking tool; it could be used from scripts
- or other programs. These % password checks also apply
- to the -unixpw_nis and -unixpw_cmd options.
-
- For the % password check, if the env. var. UNIXPW_CMD
- is set to a command then it is run as the user (assuming
- the password is correct.) The output of the command is
- not printed, the program or script must manage that by
- some other means. The exit code of x11vnc will depend
- on the exit code of the command that is run.
-
- Use -nounixpw to disable unixpw mode if it was enabled
- earlier in the cmd line (e.g. -svc mode)
-
--unixpw_nis [list] As -unixpw above, however do not use su(1) but rather
- use the traditional getpwnam(3) + crypt(3) method to
- verify passwords. All of the above -unixpw options and
- constraints apply.
-
- This mode requires that the encrypted passwords be
- readable. Encrypted passwords stored in /etc/shadow
- will be inaccessible unless x11vnc is run as root.
-
- This is called "NIS" mode simply because in most
- NIS setups user encrypted passwords are accessible
- (e.g. "ypcat passwd") by an ordinary user and so that
- user can authenticate ANY user.
-
- NIS is not required for this mode to work (only that
- getpwnam(3) return the encrypted password is required),
- but it is unlikely it will work (as an ordinary user)
- for most modern environments unless NIS is available.
- On the other hand, when x11vnc is run as root it will
- be able to to access /etc/shadow even if NIS is not
- available (note running as root is often done when
- running x11vnc from inetd and xdm/gdm/kdm).
-
- Looked at another way, if you do not want to use the
- su(1) method provided by -unixpw (i.e. su_verify()), you
- can run x11vnc as root and use -unixpw_nis. Any users
- with passwords in /etc/shadow can then be authenticated.
-
- In -unixpw_nis mode, under no circumstances is x11vnc's
- user password verifying function based on su called
- (i.e. the function su_verify() that runs /bin/su
- in a pseudoterminal to verify passwords.) However,
- if -unixpw_nis is used in conjunction with the -find
- and -create -display WAIT:... modes then, if x11vnc is
- running as root, /bin/su may be called externally to
- run the find or create commands.
-
--unixpw_cmd cmd As -unixpw above, however do not use su(1) but rather
- run the externally supplied command "cmd". The first
- line of its stdin will be the username and the second
- line the received password. If the command exits
- with status 0 (success) the VNC user will be accepted.
- It will be rejected for any other return status.
-
- Dynamic passwords and non-unix passwords, e.g. LDAP,
- can be implemented this way by providing your own custom
- helper program. Note that the remote viewer is given 3
- tries to enter the correct password, and so the program
- may be called in a row that many (or more) times.
-
- If a list of allowed users is needed to limit who can
- log in, use -unixpw [list] in addition to this option.
-
- In FINDDISPLAY and FINDCREATEDISPLAY modes the "cmd"
- will also be run with the RFB_UNIXPW_CMD_RUN env. var.
- non-empty and set to the corresponding display
- find/create command. The first two lines of input are
- the username and passwd as in the normal case described
- above. To support FINDDISPLAY and FINDCREATEDISPLAY,
- "cmd" should run the requested command as the user
- (and most likely refusing to run it if the password is
- not correct.) Here is an example script (note it has
- a hardwired bogus password "abc"!)
-
- #!/bin/sh
- # Example x11vnc -unixpw_cmd script.
- # Read the first two lines of stdin (user and passwd)
- read user
- read pass
-
- debug=0
- if [ $debug = 1 ]; then
- echo "user: $user" 1>&2
- echo "pass: $pass" 1>&2
- env | egrep -i 'rfb|vnc' 1>&2
- fi
-
- # Check if the password is valid.
- # (A real example would use ldap lookup, etc!)
- if [ "X$pass" != "Xabc" ]; then
- exit 1 # incorrect password
- fi
-
- if [ "X$RFB_UNIXPW_CMD_RUN" = "X" ]; then
- exit 0 # correct password
- else
- # Run the requested command (finddisplay)
- if [ $debug = 1 ]; then
- echo "run: $RFB_UNIXPW_CMD_RUN" 1>&2
- fi
- exec /bin/su - "$user" -c "$RFB_UNIXPW_CMD_RUN"
- fi
-
- In -unixpw_cmd mode, under no circumstances is x11vnc's
- user password verifying function based on su called
- (i.e. the function su_verify() that runs /bin/su in a
- pseudoterminal to verify passwords.) It is up to the
- supplied unixpw_cmd to do user switching if desired
- and if it has the permissions to do so.
-
--find Find the user's display using FINDDISPLAY. This
- is an alias for "-display WAIT:cmd=FINDDISPLAY".
-
- Note: if a -display occurs later on the command line
- it will override the -find setting.
-
- For this and the next few options see -display WAIT:...
- below for all of the details.
-
--finddpy Run the FINDDISPLAY program, print out the found
- display (if any) and exit. Output is like: DISPLAY=:0.0
- DISPLAY=:0.0,XPID=12345 or DISPLAY=:0.0,VT=7. XPID is
- the process ID of the found X server. VT is the Linux
- virtual terminal of the X server.
--listdpy Have the FINDDISPLAY program list all of your displays
- (i.e. all the X displays on the local machine that you
- have access rights to). x11vnc then exits.
-
--findauth [disp] Apply the -find/-finddpy heuristics to try to guess
- the XAUTHORITY file for DISPLAY 'disp'. If 'disp'
- is not supplied, then the value in the -display on
- the cmdline is used; failing that $DISPLAY is used;
- and failing that ":0" is used. x11vnc then exits.
-
- If nothing is printed out, that means no XAUTHORITY was
- found for 'disp'; i.e. failure. If "XAUTHORITY="
- is printed out, that means use the default (i.e. do
- not set XAUTHORITY). If "XAUTHORITY=/path/to/file"
- is printed out, then use that file.
-
- XDM/GDM/KDM: if you are running x11vnc as root and want
- to find the XAUTHORITY before anyone has logged into an
- X session yet, use: x11vnc -env FD_XDM=1 -findauth ...
- (This will also find the XAUTHORITY if a user is already
- logged into the X session.) When running as root,
- FD_XDM=1 will be tried if the initial -findauth fails.
-
--create First try to find the user's display using FINDDISPLAY,
- if that doesn't succeed create an X session via the
- FINDCREATEDISPLAY method. This is an alias for
- "-display WAIT:cmd=FINDCREATEDISPLAY-Xvfb".
-
- Note: if a -display occurs later on the command line
- it will override the -create setting.
-
- SSH NOTE: for both -find and -create you can (should!)
- add the "-localhost" option to force SSH tunnel access.
-
--xdummy As in -create, except Xdummy instead of Xvfb.
--xvnc As in -create, except Xvnc instead of Xvfb.
--xvnc_redirect As in -create, except Xvnc.redirect instead of Xvfb.
--xdummy_xvfb Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb
-
--create_xsrv str Sets WAIT:cmd=FINDCREATEDISPLAY-<str> Can be on cmdline
- after anything that sets WAIT:.. and other things
- (e.g. -svc, -xdmsvc) to adjust the X server list.
- Example: -svc ... -create_xsrv Xdummy,X
-
--svc Terminal services mode based on SSL access. Alias for
- -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users
- unixpw= -ssl SAVE Also "-service".
-
- Note: if a -display, -unixpw, -users, or -ssl occurs
- later on the command line it will override the -svc
- setting.
-
--svc_xdummy As -svc except Xdummy instead of Xvfb.
--svc_xvnc As -svc except Xvnc instead of Xvfb.
--svc_xdummy_xvfb As -svc with Xdummy,Xvfb.
-
--xdmsvc Display manager Terminal services mode based on SSL.
- Alias for -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp
- -unixpw -users unixpw= -ssl SAVE Also "-xdm_service".
-
- Note: if a -display, -unixpw, -users, or -ssl occurs
- later on the command line it will override the -xdmsvc
- setting.
-
- To create a session a user will have to first log in
- to the -unixpw dialog and then log in again to the
- XDM/GDM/KDM prompt. Subsequent re-connections will
- only require the -unixpw password. See the discussion
- under -display WAIT:... for more details about XDM,
- etc configuration.
-
- Remember to enable XDMCP in the xdm-config, gdm.conf,
- or kdmrc configuration file. See -display WAIT: for
- more info.
-
--sshxdmsvc Display manager Terminal services mode based on SSH.
- Alias for -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp
- -localhost.
-
- The -localhost option constrains connections to come
- in via a SSH tunnel (which will require a login).
- To create a session a user will also have to log into
- the XDM GDM KDM prompt. Subsequent re-connections will
- only only require the SSH login. See the discussion
- under -display WAIT:... for more details about XDM,
- etc configuration.
-
- Remember to enable XDMCP in the xdm-config, gdm.conf,
- or kdmrc configuration file. See -display WAIT: for
- more info.
-
--unixpw_system_greeter Present a "Press 'Escape' for System Greeter" option
- to the connecting VNC client in combined -unixpw
- and xdmcp FINDCREATEDISPLAY modes (e.g. -xdmsvc).
-
- Normally in a -unixpw mode the VNC client must
- supply a valid username and password to gain access.
- However, if -unixpw_system_greeter is supplied AND
- the FINDCREATEDISPLAY command matches 'xdmcp', then
- the user has the option to press Escape and then get a
- XDM/GDM/KDM login/greeter panel instead. They will then
- supply a username and password directly to the greeter.
-
- Otherwise, in xdmcp FINDCREATEDISPLAY mode the user
- must supply his username and password TWICE. First to
- the initial unixpw login dialog, and second to the
- subsequent XDM/GDM/KDM greeter. Note that if the user
- re-connects and supplies his username and password in
- the unixpw dialog the xdmcp greeter is skipped and
- he is connected directly to his existing X session.
- So the -unixpw_system_greeter option avoids the extra
- password at X session creation time.
-
- Example: x11vnc -xdmsvc -unixpw_system_greeter
- See -unixpw and -display WAIT:... for more info.
-
- The special options after a colon at the end of the
- username (e.g. user:solid) described under -display
- WAIT: are also applied in this mode if they are typed
- in before the user hits Escape. The username is ignored
- but the colon options are not.
-
- The default message is 2 lines in a small font, set
- the env. var. X11VNC_SYSTEM_GREETER1=true for a 1 line
- message in a larger font.
-
- If the user pressed Escape the FINDCREATEDISPLAY command
- will be run with the env. var. X11VNC_XDM_ONLY=1.
-
- Remember to enable XDMCP in the xdm-config, gdm.conf,
- or kdmrc configuration file. See -display WAIT: for
- more info.
-
--redirect port As in FINDCREATEDISPLAY-Xvnc.redirect mode except
- redirect immediately (i.e. without X session finding
- or creation) to a VNC server listening on port. You
- can also supply host:port to redirect to a different
- machine.
-
- If 0 <= port < 200 it is taken as a VNC display (5900 is
- added to get the actual port), if port < 0 then -port
- is used.
-
- Probably the only reason to use the -redirect option
- is in conjunction with SSL support, e.g. -ssl SAVE.
- This provides an easy way to add SSL encryption to a VNC
- server that does not support SSL (e.g. Xvnc or vnc.so)
- In fact, the protocol does not even need to be VNC,
- and so "-rfbport port1 -ssl SAVE -redirect host:port2"
- can act as a replacement for stunnel(1).
-
- This mode only allows one redirected connection.
- The -forever option does not apply. Use -inetd or
- -loop for persistent service.
-
--display_WAIT :... A special usage mode for the normal -display option.
- Useful with -unixpw, but can be used independently
- of it. If the display string begins with WAIT: then
- x11vnc waits until a VNC client connects before opening
- the X display (or -rawfb device).
-
- This could be useful for delaying opening the display
- for certain usage modes (say if x11vnc is started at
- boot time and no X server is running or users logged
- in yet).
-
- If the string is, e.g. WAIT:0.0 or WAIT:1, i.e. "WAIT"
- in front of a normal X display, then that indicated
- display is used.
-
- One can also insert a geometry between colons, e.g.
- WAIT:1280x1024:... to set the size of the display the
- VNC client first attaches to since some VNC viewers
- will not automatically adjust to a new framebuffer size.
-
- A more interesting case is like this:
-
- WAIT:cmd=/usr/local/bin/find_display
-
- in which case the command after "cmd=" is run to
- dynamically work out the DISPLAY and optionally the
- XAUTHORITY data. The first line of the command output
- must be of the form DISPLAY=<xdisplay>. On Linux
- if the virtual terminal is known append ",VT=n" to
- this string and the chvt(1) program will also be run.
- Any remaining output is taken as XAUTHORITY data.
- It can be either of the form XAUTHORITY=<file> or raw
- xauthority data for the display. For example;
-
- xauth extract - $DISPLAY"
-
- NOTE: As specified in the previous paragraph, you can
- supply your own WAIT:cmd=... program or script, BUT
- there are two very useful *BUILT-IN* ones: FINDDISPLAY
- (alias -find above) and FINDCREATEDISPLAY (alias -create
- above.) Most people use these instead of creating
- their own script. Read the following (especially the
- BUILT-IN modes sections) to see how to configure these
- two useful builtin -display WAIT: modes.
-
- In the case of -unixpw (and -unixpw_nis only if x11vnc
- is running as root), then the cmd= command is run
- as the user who just authenticated via the login and
- password prompt.
-
- In the case of -unixpw_cmd, the commands will also be
- run as the logged-in user, as long as the user-supplied
- helper program supports RFB_UNIXPW_CMD_RUN (see the
- -unixpw_cmd option.)
-
- Also in the case of -unixpw, the user logging in can
- place a colon at the end of her username and supply
- a few options: scale=, scale_cursor= (or sc=), solid
- (or so), id=, clear_mods (or cm), clear_keys (or
- ck), clear_all (or ca), repeat, speeds= (or sp=),
- readtimeout= (or rd=), viewonly (or vo), nodisplay=
- (or nd=), rotate= (or ro=), or noncache (or nc),
- all separated by commas if there is more than one.
- After the user logs in successfully, these options will
- be applied to the VNC screen. For example,
-
- login: fred:scale=3/4,sc=1,repeat
- Password: ...
-
- login: runge:sp=modem,rd=120,solid
-
- for convenience m/n implies scale= e.g. fred:3/4 If you
- type and enter your password incorrectly, to retrieve
- your long "login:" line press the Up arrow once
- (before typing anything else).
-
- Most of these colon options only apply to the builtin
- FINDDISPLAY and FINDCREATEDISPLAY modes, but note
- that they are passed to the extrenal command in the
- environment as well and so could be used.
-
- In the login panel, press F1 to get a list of the
- available options that you can add after the username.
-
- Another option is "geom=WxH" or "geom=WxHxD" (or
- ge=). This only has an effect in FINDCREATEDISPLAY
- mode when a virtual X server such as Xvfb is going
- to be created. It sets the width and height of
- the new display, and optionally the color depth as
- well.
-
- You can also supply "gnome", "kde", "twm",
- "fvwm", "mwm", "dtwm", "wmaker", "xfce",
- "lxde", "enlightenment", "Xsession", or
- "failsafe" (same as "xterm") to have the created
- display use that mode for the user session.
-
- Specify "tag=..." to set the unique FD_TAG desktop
- session tag described below. Note: this option will
- be ignored if the FD_TAG env. var. is already set or
- if the viewer-side supplied value is not completely
- composed of alphanumeric or '_' or '-' characters.
-
- User preferences file: Instead of having the user type
- in geom=WxH,... etc. every time he logs in to find
- or create his X session, if you set FD_USERPREFS to
- a string that does not contain the "/" character,
- then the user's home directory is prepended to that
- string and if the file exists its first line is read
- and appended to any options he supplied at the login:
- prompt. For example -env FD_USERPREFS=.x11vnc_create
- and the user put "geom=1600x1200" in his
- ~/.x11vnc_create file.
-
- To disable the option setting set the environment
- variable X11VNC_NO_UNIXPW_OPTS=1 before starting x11vnc.
- To set any other options, the user can use the gui
- (x11vnc -gui connect) or the remote control method
- (x11vnc -R opt:val) during his VNC session.
-
- So we see the combination of -display WAIT:cmd=... and
- -unixpw allows automatic pairing of an unix
- authenticated VNC user with his desktop. This could
- be very useful on SunRays and also any system where
- multiple users share a given machine. The user does
- not need to remember special ports or passwords set up
- for his desktop and VNC.
-
- A nice way to use WAIT:cmd=... is out of inetd(8)
- (it automatically forks a new x11vnc for each user).
- You can have the x11vnc inetd spawned process run as,
- say, root or nobody. When run as root (for either inetd
- or display manager), you can also supply the option
- "-users unixpw=" to have the x11vnc process switch to
- the user as well. Note: there will be a 2nd SSL helper
- process that will not switch, but it is only encoding
- and decoding the encrypted stream at that point.
-
- BUILT-IN modes:
-
- -- Automatic Finding of User X Sessions --
-
- As a special case, WAIT:cmd=FINDDISPLAY will run a
- script that works on most Unixes to determine a user's
- DISPLAY variable and xauthority data (see who(1)).
-
- NOTE: The option "-find" is an alias for this mode.
-
- To have this default script printed to stdout (e.g. for
- customization) run with WAIT:cmd=FINDDISPLAY-print To
- have the script run to print what display it would find
- use "-finddpy" or WAIT:cmd=FINDDISPLAY-run
-
- The standard script runs xdpyinfo(1) run on potential
- displays. If your X server(s) have a login greeter
- that exclusively grabs the Xserver, then xdpyinfo
- blocks forever and this mode will not work. See
- www.karlrunge.com/x11vnc/faq.html#faq-display-manager
- for how to disable this for dtgreet on Solaris and
- possibly for other greeters.
-
- In -find/cmd=FINDDISPLAY mode, if you set FD_XDM=1,
- e.g. 'x11vnc -env FD_XDM=1 -find ...' and x11vnc is
- running as root (e.g. inetd) then it will try to find
- the XAUTHORITY file of a running XDM/GDM/KDM login
- greeter (i.e. no user has logged into an X session yet.)
-
- As another special case, WAIT:cmd=HTTPONCE will allow
- x11vnc to service one http request and then exit.
- This is usually done in -inetd mode to run on, say,
- port 5800 and allow the Java vncviewer to be downloaded
- by client web browsers. For example:
-
- 5815 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc
-\
- -inetd -q -http_ssl -prog /.../x11vnc \
- -display WAIT:cmd=HTTPONCE
-
- Where /.../x11vnc is the full path to x11vnc.
- It is used in the Apache SSL-portal example (see FAQ).
-
- In this mode you can set X11VNC_SKIP_DISPLAY to a
- comma separated list of displays (e.g. ":0,:1") to
- ignore in the finding process. The ":" is optional.
- Ranges n-m e.g. 0-20 can also be supplied. This string
- can also be set by the connecting user via "nd="
- using "+" instead of "," If "nd=all" or you set
- X11VNC_SKIP_DISPLAY=all then all display finding fails
- as if you set X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (below.)
-
- On some systems lsof(1) can be very slow. Set the
- env. var. FIND_DISPLAY_NO_LSOF=1 to skip using lsof to
- try to find the Linux VT the X server is running on.
- set FIND_DISPLAY_NO_VT_FIND=1 to avoid looking at all.
-
- -- Automatic Creation of User X Sessions --
-
- An interesting option is WAIT:cmd=FINDCREATEDISPLAY
- that is like FINDDISPLAY in that is uses the same method
- to find an existing display. However, if it does not
- find one it will try to *start* up an X server session
- for the user. This is the only time x11vnc tries to
- actually start up an X server.
-
- NOTE: The option "-create" is an alias for this mode.
-
- It will start looking for an open display number at :20
- Override via X11VNC_CREATE_STARTING_DISPLAY_NUMBER=n
- By default 80 X displays are allowed (i.e. going to :99)
- Override via X11VNC_CREATE_MAX_DISPLAYS=n
-
- For its heuristics, the create display script sets
- LC_ALL=C so that command output is uniform. By default
- it will try to restore LC_ALL right before starting the
- user session. However, if you don't mind it keeping
- LC_ALL=C set the env. var.: X11VNC_CREATE_LC_ALL_C_OK=1
-
- By default FINDCREATEDISPLAY will try Xvfb and then
- Xdummy:
-
- The Xdummy wrapper is part of the x11vnc source code
- (x11vnc/misc/Xdummy) It should be available in PATH
- and have run "Xdummy -install" once to create the
- shared library. Xdummy only works on Linux. As of
- 12/2009 it no longer needs to be run as root, and the
- default is to not run as root. In some circumstances
- permissions may require running it as root, in these
- cases specify FD_XDUMMY_RUN_AS_ROOT=1, this is the same
- as supplying -root to the Xdummy cmdline.
-
- Xvfb is available on most platforms and does not
- require root.
-
- An advantage of Xdummy over Xvfb is that Xdummy supports
- RANDR dynamic screen resizing.
-
- When x11vnc exits (i.e. user disconnects) the X
- server session stays running in the background.
- The FINDDISPLAY will find it directly next time.
- The user must exit the X session in the usual way for
- it to terminate (or kill the X server process if all
- else fails).
-
- To troubleshoot the FINDCREATEDISPLAY mechanism,
- set the following env. var. to an output log file,
- e.g -env CREATE_DISPLAY_OUTPUT=/tmp/mydebug.txt
-
- So this is a somewhat odd mode for x11vnc in that it
- will start up and poll virtual X servers! This can
- be used from, say, inetd(8) to provide a means of
- definitely getting a desktop (either real or virtual)
- on the machine. E.g. a desktop service:
-
- 5900 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc
- -inetd -q -http -ssl SAVE -unixpw -users unixpw=\
- -passwd secret -prog /.../x11vnc \
- -display WAIT:cmd=FINDCREATEDISPLAY
-
- Where /.../x11vnc is the full path to x11vnc.
-
- See the -svc/-service option alias above.
-
- If for some reason you do not want x11vnc to ever
- try to find an existing display set the env. var
- X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (also -env ...)
- This is the same as setting X11VNC_SKIP_DISPLAY=all or
- supplying "nd=all" after "username:"
-
- Use WAIT:cmd=FINDCREATEDISPLAY-print to print out the
- script that is used for this.
-
- You can specify the preferred X server order via e.g.,
- WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb,X and/or leave
- out ones you do not want. The the case "X" means try
- to start up a real, hardware X server using xinit(1)
- or startx(1). If there is already an X server running
- the X case may only work on Linux (see startx(1)).
-
- "Xvnc" will start up a VNC X server (real-
- or tight-vnc, e.g. use if Xvfb is not available).
- "Xsrv" will start up the server program in the
- variable "FD_XSRV" if it is non-empty. You can make
- this be a wrapper script if you like (it must handle :N,
- -geometry, and -depth and other X server options).
-
- You can set the environment variable FD_GEOM (or
- X11VNC_CREATE_GEOM) to WxH or WxHxD to set the width
- and height and optionally the color depth of the
- created display. You can also set FD_SESS to be the
- session (short name of the windowmanager: kde, gnome,
- twm, failsafe, etc.). FD_OPTS contains extra options
- to pass to the X server. You can also set FD_PROG to
- be the full path to the session/windowmanager program.
-
- More FD tricks: FD_CUPS=port or FD_CUPS=host:port
- will set the cups printing environment. Similarly for
- FD_ESD=port or FD_ESD=host:port for esddsp sound
- redirection. Set FD_EXTRA to a command to be run a
- few seconds after the X server starts up. Set FD_TAG
- to be a unique name for the session, it is set as an
- X property, that makes FINDDISPLAY only find sessions
- with that tag value.
-
- Set FD_XDMCP_IF to the network interface that the
- display manager is running on; default is 'localhost'
- but you may need to set it to '::1' on some IPv6 only
- systems or misconfigured display managers.
-
- If you want the FINDCREATEDISPLAY session to contact an
- XDMCP login manager (xdm/gdm/kdm) on the same machine,
- then use "Xvfb.xdmcp" instead of "Xvfb", etc.
- The user will have to supply his username and password
- one more time (but he gets to select his desktop type
- so that can be useful). For this to work, you will
- need to enable localhost XDMCP (udp port 177) for the
- display manager. This seems to be:
-
- for gdm in gdm.conf: Enable=true in section [xdmcp]
- for kdm in kdmrc: Enable=true in section [Xdmcp]
- for xdm in xdm-config: DisplayManager.requestPort: 177
-
- See the shorthand options above "-svc", "-xdmsvc"
- and "-sshxdmsvc" that specify the above options for
- some useful cases.
-
- If you set the env. var WAITBG=1 x11vnc will go into
- the background once listening in wait mode.
-
- Another special mode is FINDCREATEDISPLAY-Xvnc.redirect,
- (or FINDDISPLAY-Xvnc.redirect). In this case it will
- start up Xvnc as above if needed, but instead of
- polling it in its normal way, it simply does a socket
- redirection of the connected VNC viewer to the Xvnc.
-
- So in Xvnc.redirect x11vnc does no VNC but merely
- transfers the data back and forth. This should be
- faster then x11vnc's polling method, but not as fast
- as connecting directly to the Xvnc with the VNC Viewer.
- The idea here is to take advantage of x11vnc's display
- finding/creating scheme, SSL, and perhaps a few others.
- Most of x11vnc's options do not apply in this mode.
-
- Xvnc.redirect should also work for the vnc.so X server
- module for the h/w display however it will work only
- for finding the display and the user must already be
- logged into the X console.
-
--vencrypt mode The VeNCrypt extension to the VNC protocol allows
- encrypted SSL/TLS connections. If the -ssl mode is
- enabled, then VeNCrypt is enabled as well BY DEFAULT
- (they both use a SSL/TLS tunnel, only the protocol
- handshake is a little different.)
-
- To control when and how VeNCrypt is used, specify the
- mode string. If mode is "never", then VeNCrypt is
- not used. If mode is "support" (the default) then
- VeNCrypt is supported. If mode is "only", then the
- similar and older ANONTLS protocol is not simultaneously
- supported. x11vnc's normal SSL mode (vncs://) will be
- supported under -ssl unless you set mode to "force".
-
- If mode is prefixed with "nodh:", then Diffie Hellman
- anonymous key exchange is disabled. If mode is prefixed
- with "nox509:", then X509 key exchange is disabled.
-
- To disable all Anonymous Diffie-Hellman access
- (susceptible to Man-In-The-Middle attack) you will need
- to supply "-vencrypt nodh:support -anontls never"
- or "-vencrypt nodh:only"
-
- If mode is prefixed with "newdh:", then new Diffie
- Hellman parameters are generated for each connection
- (this can be time consuming: 1-60 secs; see -dhparams
- below for a faster way) rather than using the
- fixed values in the program. Using fixed, publicly
- known values is not known to be a security problem.
- This setting applies to ANONTLS as well.
-
- Long example: -vencrypt newdh:nox509:support
-
- Also, if mode is prefixed with "plain:", then
- if -unixpw mode is active the VeNCrypt "*Plain"
- username+passwd method is enabled for Unix logins.
- Otherwise in -unixpw mode the normal login panel is
- provided.
-
- You *MUST* supply the -ssl option for VeNCrypt to
- be active. The -vencrypt option only fine-tunes its
- operation.
-
--anontls mode The ANONTLS extension to the VNC protocol allows
- encrypted SSL/TLS connections. If the -ssl mode is
- enabled, then ANONTLS is enabled as well BY DEFAULT
- (they both use a SSL/TLS tunnel, only the protocol
- handshake is a little different.)
-
- ANONTLS is an older SSL/TLS mode introduced by vino.
-
- It is referred to as 'TLS' for its registered VNC
- security-type name, but we use the more descriptive
- 'ANONTLS' here because it provides only Anonymous
- Diffie-Hellman encrypted connections, and hence no
- possibility for certificate authentication.
-
- To control when and how ANONTLS is used, specify the
- mode string. If mode is "never", then ANONTLS is not
- used. If mode is "support" (the default) then ANONTLS
- is supported. If mode is "only", then the similar
- VeNCrypt protocol is not simultaneously supported.
- x11vnc's normal SSL mode (vncs://) will be supported
- under -ssl unless you set mode to "force".
-
- If mode is prefixed with "newdh:", then new Diffie
- Hellman parameters are generated for each connection
- (this can be time consuming: 1-60 secs; see -dhparams
- below for a faster way) rather than using the
- fixed values in the program. Using fixed, publicly
- known values is not known to be a security problem.
- This setting applies to VeNCrypt as well. See the
- description of "plain:" under -vencrypt.
-
- Long example: -anontls newdh:plain:support
-
- You *MUST* supply the -ssl option for ANONTLS to
- be active. The -anontls option only fine-tunes its
- operation.
-
--sslonly Same as: "-vencrypt never -anontls never" i.e. it
- disables the VeNCrypt and ANONTLS encryption methods
- and only allows standard SSL tunneling. You must also
- supply the -ssl ... option (see below.)
-
-
--dhparams file For some operations a set of Diffie Hellman parameters
- (prime and generator) is needed. If so, use the
- parameters in "file". In particular, the VeNCrypt and
- ANONTLS anonymous DH mode need them. By default a
- fixed set is used. If you do not want to do that you
- can specify "newdh:" to the -vencrypt and -anontls
- options to generate a new set each session. If that
- is too slow for you, use -dhparams file to a set you
- created manually via "openssl dhparam -out file 1024"
-
--nossl Disable the -ssl option (see below). Since -ssl is off
- by default -nossl would only be used on the commandline
- to unset any *earlier* -ssl option (or -svc...)
-
--ssl [pem] Use the openssl library (www.openssl.org) to provide a
- built-in encrypted SSL/TLS tunnel between VNC viewers
- and x11vnc. This requires libssl support to be
- compiled into x11vnc at build time. If x11vnc is not
- built with libssl support it will exit immediately when
- -ssl is prescribed. See the -stunnel option below for
- an alternative.
-
- The VNC Viewer-side needs to support SSL/TLS as well.
- See this URL and also the discussion below for
- ideas on how to enable SSL support for the viewer:
- http://www.karlrunge.com/x11vnc/faq.html#faq-ssl-tun
- nel-viewers . x11vnc provides an SSL enabled Java
- viewer applet in the classes/ssl directory (-http or
- -httpdir options.) The SSVNC viewer package supports
- SSL tunnels too.
-
- If the VNC Viewer supports VeNCrypt or ANONTLS (vino's
- encryption mode) they are also supported by the -ssl
- mode (see the -vencrypt and -anontls options for more
- info; use -sslonly to disable both of them.)
-
- Use "-ssl /path/to/mycert.pem" to specify an SSL
- certificate file in PEM format to use to identify and
- provide a key for this server. See openssl(1) for more
- info about PEMs and the -sslGenCert and "-ssl SAVE"
- options below for how to create them.
-
- The connecting VNC viewer SSL tunnel can (at its option)
- authenticate this server if it has the public key part
- of the certificate (or a common certificate authority,
- CA, is a more sophisticated way to verify this server's
- cert, see -sslGenCA below). This authentication is
- done to prevent Man-In-The-Middle attacks. Otherwise,
- if the VNC viewer simply accepts this server's key
- WITHOUT verification, the traffic is protected from
- passive sniffing on the network, but *NOT* from
- Man-In-The-Middle attacks. There are hacker tools
- like dsniff/webmitm and cain that implement SSL
- Man-In-The-Middle attacks.
-
- If [pem] is empty or the string "SAVE" then the
- openssl(1) command must be available to generate the
- certificate the first time. A self-signed certificate
- is generated (see -sslGenCA and -sslGenCert for use
- of a Certificate Authority.) It will be saved to the
- file ~/.vnc/certs/server.pem. On subsequent calls if
- that file already exists it will be used directly.
-
- Use "SAVE_NOPROMPT" to avoid being prompted to
- protect the generated key with a passphrase. However in
- -inetd and -bg modes there will be no prompting for a
- passphrase in either case.
-
- If [pem] is "SAVE_PROMPT" the server.pem certificate
- will be created based on your answers to its prompts for
- all info such as OrganizationalName, CommonName, etc.
-
- Use "SAVE-<string>" and "SAVE_PROMPT-<string>"
- to refer to the file ~/.vnc/certs/server-<string>.pem
- instead (it will be generated if it does not already
- exist). E.g. "SAVE-charlie" will store to the file
- ~/.vnc/certs/server-charlie.pem
-
- Examples: x11vnc -ssl SAVE -display :0 ...
- x11vnc -ssl SAVE-someother -display :0 ...
-
- If [pem] is "TMP" and the openssl(1) utility
- command exists in PATH, then a temporary, self-signed
- certificate will be generated for this session. If
- openssl(1) cannot be used to generate a temporary
- certificate x11vnc exits immediately. The temporary
- cert will be discarded when x11vnc exits.
-
- If successful in using openssl(1) to generate a
- temporary certificate in "SAVE" or "TMP" creation
- modes, the public part of it will be displayed to stderr
- (e.g. one could copy it to the client-side to provide
- authentication of the server to VNC viewers.)
-
- NOTE: In "TMP" mode, unless you safely copy the
- public part of the temporary Cert to the viewer for
- authenticate *every time* (unlikely...), then only
- passive sniffing attacks are prevented and you are
- still open to Man-In-The-Middle attacks. This is
- why the default "SAVE" mode is preferred (and more
- sophisticated CA mode too). Only with saved keys AND
- the VNC viewer authenticating them (via the public
- certificate), are Man-In-The-Middle attacks prevented.
-
- If [pem] is "ANON" then the Diffie-Hellman anonymous
- key exchange method is used. In this mode there
- are *no* SSL certificates and so it is not possible
- to authenticate either the VNC server or VNC client.
- Thus only passive network sniffing attacks are avoided:
- the "ANON" method is susceptible to Man-In-The-Middle
- attacks. "ANON" is not recommended; instead use
- a SSL PEM you created or the default "SAVE" method.
-
- See -ssldir below to use a directory besides the
- default ~/.vnc/certs
-
- If your x11vnc binary was not compiled with OpenSSL
- library support, use of the -ssl option will induce an
- immediate failure and exit. For such binaries, consider
- using the -stunnel option for SSL encrypted connections.
-
- Misc Info: In temporary cert creation mode "TMP", set
- the env. var. X11VNC_SHOW_TMP_PEM=1 to have x11vnc print
- out the entire certificate, including the PRIVATE KEY
- part, to stderr. There are better ways to get/save this
- info. See "SAVE" above and "-sslGenCert" below.
-
--ssltimeout n Set SSL read timeout to n seconds. In some situations
- (i.e. an iconified viewer in Windows) the viewer stops
- talking and the connection is dropped after the default
- timeout (25s for about the first minute, 43200s later).
- Set to zero to poll forever. Set to a negative value
- to use the builtin setting.
-
- Note that this value does NOT apply to the *initial* ssl
- init connection. The default timeout for that is 20sec.
- Use -env SSL_INIT_TIMEOUT=n to modify it.
-
--sslnofail Exit at the first SSL connection failure. Useful when
- scripting SSL connections (e.g. x11vnc is started via
- ssh) and you do not want x11vnc waiting around for more
- connections, tying up ports, etc.
-
--ssldir dir Use "dir" as an alternate ssl certificate and key
- management toplevel directory. The default is
- ~/.vnc/certs
-
- This directory is used to store server and other
- certificates and keys and also other materials. E.g. in
- the simplest case, "-ssl SAVE" will store the x11vnc
- server cert in dir/server.pem
-
- Use of alternate directories via -ssldir allows you to
- manage multiple VNC Certificate Authority (CA) keys.
- Another use is if ~/.vnc/cert is on an NFS share you
- might want your certificates and keys to be on a local
- filesystem to prevent network snooping (for example
- -ssldir /var/lib/x11vnc-certs).
-
- -ssldir affects nearly all of the other -ssl* options,
- e.g. -ssl SAVE, -sslGenCert, etc..
-
--sslverify path For either of the -ssl or -stunnel modes, use "path"
- to provide certificates to authenticate incoming VNC
- *Client* connections (normally only the server is
- authenticated in SSL.) This can be used as a method
- to replace standard password authentication of clients.
-
- If "path" is a directory it contains the client (or CA)
- certificates in separate files. If path is a file,
- it contains one or more certificates. See special tokens
- below. These correspond to the "CApath = dir" and
- "CAfile = file" stunnel options. See the stunnel(8)
- manpage for details.
-
- Examples:
- x11vnc -ssl -sslverify ~/my.crt
- x11vnc -ssl -sslverify ~/my_pem_dir/
-
- Note that if path is a directory, it must contain
- the certs in separate files named like <HASH>.0, where
- the value of <HASH> is found by running the command
- "openssl x509 -hash -noout -in file.crt". Evidently
- one uses <HASH>.1 if there is a collision...
-
- The the key-management utility "-sslCertInfo HASHON"
- and "-sslCertInfo HASHOFF" will create/delete these
- hashes for you automatically (via symlink) in the HASH
- subdirs it manages. Then you can point -sslverify to
- the HASH subdir.
-
- Special tokens: in -ssl mode, if "path" is not a file or
- a directory, it is taken as a comma separated list of
- tokens that are interpreted as follows:
-
- If a token is "CA" that means load the CA/cacert.pem
- file from the ssl directory. If a token is "clients"
- then all the files clients/*.crt in the ssl directory
- are loaded. Otherwise the file clients/token.crt
- is attempted to be loaded. As a kludge, use a token
- like ../server-foo to load a server cert if you find
- that necessary.
-
- Use -ssldir to use a directory different from the
- ~/.vnc/certs default.
-
- Note that if the "CA" cert is loaded you do not need
- to load any of the certs that have been signed by it.
- You will need to load any additional self-signed certs
- however.
-
- Examples:
- x11vnc -ssl -sslverify CA
- x11vnc -ssl -sslverify self:fred,self:jim
- x11vnc -ssl -sslverify CA,clients
-
- Usually "-sslverify CA" is the most effective.
- See the -sslGenCA and -sslGenCert options below for
- how to set up and manage the CA framework.
-
-
-
- NOTE: the following utilities, -sslGenCA, -sslGenCert,
- -sslEncKey, -sslCertInfo, and -sslCRL are provided for
- completeness, but for casual usage they are overkill.
-
- They provide VNC Certificate Authority (CA) key creation
- and server / client key generation and signing. So they
- provide a basic Public Key management framework for
- VNC-ing with x11vnc. (note that they require openssl(1)
- be installed on the system)
-
- However, the simplest usage mode, "-ssl TMP" (where
- x11vnc automatically generates its own, self-signed,
- temporary key and the VNC viewers always accept it,
- e.g. accepting via a dialog box) is probably safe enough
- for most scenarios. CA management is not needed.
-
- To protect against Man-In-The-Middle attacks the "TMP"
- mode can be improved by using "-ssl SAVE" (same as
- "-ssl", i.e. the default) to have x11vnc create a
- longer term self-signed certificate, and then (safely)
- copy the corresponding public key cert to the desired
- client machines (care must be taken the private key part
- is not stolen; you will be prompted for a passphrase).
-
- So keep in mind no CA key creation or management
- (-sslGenCA and -sslGenCert) is needed for either of
- the above two common usage modes.
-
- One might want to use -sslGenCA and -sslGenCert
- if you had a large number of VNC client and server
- workstations. That way the administrator could generate
- a single CA key with -sslGenCA and distribute its
- certificate part to all of the workstations.
-
- Next, he could create signed VNC server keys
- (-sslGenCert server ...) for each workstation or user
- that then x11vnc would use to authenticate itself to
- any VNC client that has the CA cert.
-
- Optionally, the admin could also make it so the
- VNC clients themselves are authenticated to x11vnc
- (-sslGenCert client ...) For this -sslverify would be
- pointed to the CA cert (and/or self-signed certs).
-
- x11vnc will be able to use all of these cert and
- key files. On the VNC client side, they will need to
- be "imported" somehow. Web browsers have "Manage
- Certificates" actions as does the Java applet plugin
- Control Panel. stunnel can also use these files (see
- the ss_vncviewer example script in the FAQ and SSVNC.)
-
--sslCRL path Set the Certificate Revocation Lists (CRL) to "path".
- This setting applies for both -ssl and -stunnel modes.
-
- If path is a file, the file contains one or more CRLs
- in PEM format. If path is a directory, it contains
- hash named files of CRLs in the usual OpenSSL manner.
- See the OpenSSL and stunnel(8) documentation for
- more info.
-
- This option only applies if -sslverify has been
- supplied: it checks for revocation along the
- certificate chain used to verify the VNC client.
- The -sslCRL setting will be ignored when -sslverify is
- not specified.
-
- Note that if a CRL's expiration date has passed, all
- SSL connections will fail regardless of if they are
- related to the subject of the CRL or not.
-
- Only rarely will one's x11vnc -ssl infrastructure be so
- large that this option would be useful (since normally
- maintaining the contents of the -sslverify file or
- directory should be enough.) However, when using
- x11vnc with a Certificate Authority (see -sslGenCA)
- to authenticate Clients via SSL/TLS, the -sslCRL option
- can be useful to revoke users' certs whose private SSL
- keys were lost or stolen (e.g. laptop.) This way a new
- CA cert+key does not need to be created and new signed
- client keys generated and distributed to all users.
-
- To create a CRL file with revoked certificates the
- commands 'openssl ca -revoke ...' and 'openssl ca
- -gencrl ...' are useful. (Run them in ~/.vnc/certs)
-
--sslGenCA [dir] Generate your own Certificate Authority private key,
- certificate, and other files in directory [dir].
- x11vnc then exits.
-
- If [dir] is not supplied, a -ssldir setting is used,
- or otherwise ~/.vnc/certs is used.
-
- This command also creates directories where server and
- client certs and keys will be stored. The openssl(1)
- program must be installed on the system and available
- in PATH.
-
- After the CA files and directories are created the
- x11vnc command exits; the VNC server is not run.
-
- You will be prompted for information to put into the CA
- certificate. The info does not have to be accurate just
- as long as clients accept the cert for VNC connections.
- You will also need to supply a passphrase of at least
- 4 characters for the CA private key.
-
- Once you have generated the CA you can distribute
- its certificate part, [dir]/CA/cacert.pem, to other
- workstations where VNC viewers will be run. One will
- need to "import" this certificate in the applications,
- e.g. Web browser, Java applet plugin, stunnel, etc.
- Next, you can create and sign keys using the CA with
- the -sslGenCert option below.
-
- Examples:
- x11vnc -sslGenCA
- x11vnc -sslGenCA ~/myCAdir
- x11vnc -ssldir ~/myCAdir -sslGenCA
-
- (the last two lines are equivalent)
-
--sslGenCert type name Generate a VNC server or client certificate and private
- key pair signed by the CA created previously with
- -sslGenCA. The openssl(1) program must be installed
- on the system and available in PATH.
-
- After the Certificate is generated x11vnc exits; the
- VNC server is not run.
-
- The type of key to be generated is the string "type".
- It is either "server" (i.e. for use by x11vnc) or
- "client" (for a VNC viewer). Note that typically
- only "server" is used: the VNC clients authenticate
- themselves by a non-public-key method (e.g. VNC or
- unix password). "type" is required.
-
- An arbitrary default name you want to associate with
- the key is supplied by the "name" string. You can
- change it at the various prompts when creating the key.
- "name" is optional.
-
- If name is left blank for clients keys then "nobody"
- is used. If left blank for server keys, then the
- primary server key: "server.pem" is created (this
- is the saved one referenced by "-ssl SAVE" when the
- server is started)
-
- If "name" begins with the string "self:" then
- a self-signed certificate is created instead of one
- signed by your CA key.
-
- If "name" begins with the string "req:" then only a
- key (.key) and a certificate signing *request* (.req)
- are generated. You can then send the .req file to
- an external CA (even a professional one, e.g. Thawte)
- and then combine the .key and the received cert into
- the .pem file with the same basename.
-
- The distinction between "server" and "client" is
- simply the choice of output filenames and sub-directory.
- This makes it so the -ssl SAVE-name option can easily
- pick up the x11vnc PEM file this option generates.
- And similarly makes it easy for the -sslverify option
- to pick up your client certs.
-
- There is nothing special about the filename or directory
- location of either the "server" and "client" certs.
- You can rename the files or move them to wherever
- you like.
-
- Precede this option with -ssldir [dir] to use a
- directory other than the default ~/.vnc/certs You will
- need to run -sslGenCA on that directory first before
- doing any -sslGenCert key creation.
-
- Note you cannot recreate a cert with exactly the same
- distiguished name (DN) as an existing one. To do so,
- you will need to edit the [dir]/CA/index.txt file to
- delete the line.
-
- Similar to -sslGenCA, you will be prompted to fill
- in some information that will be recorded in the
- certificate when it is created.
-
- Tip: if you know the fully-qualified hostname other
- people will be connecting to, you can use that as the
- CommonName "CN" to avoid some applications (e.g. web
- browsers and java plugin) complaining that it does not
- match the hostname.
-
- You will also need to supply the CA private key
- passphrase to unlock the private key created from
- -sslGenCA. This private key is used to sign the server
- or client certificate.
-
- The "server" certs can be used by x11vnc directly by
- pointing to them via the -ssl [pem] option. The default
- file will be ~/.vnc/certs/server.pem. This one would
- be used by simply typing -ssl SAVE. The pem file
- contains both the certificate and the private key.
- server.crt file contains the cert only.
-
- The "client" cert + private key file will need
- to be copied and imported into the VNC viewer
- side applications (Web browser, Java plugin,
- stunnel, etc.) Once that is done you can delete the
- "client" private key file on this machine since
- it is only needed on the VNC viewer side. The,
- e.g. ~/.vnc/certs/clients/<name>.pem contains both
- the cert and private key. The <name>.crt contains the
- certificate only.
-
- NOTE: It is very important to know one should
- generate new keys with a passphrase. Otherwise if an
- untrusted user steals the key file he could use it to
- masquerade as the x11vnc server (or VNC viewer client).
- You will be prompted whether to encrypt the key with
- a passphrase or not. It is recommended that you do.
- One inconvenience to a passphrase is that it must
- be typed in EVERY time x11vnc or the client app is
- started up.
-
- Examples:
-
- x11vnc -sslGenCert server
- x11vnc -ssl SAVE -display :0 ...
-
- and then on viewer using ss_vncviewer stunnel wrapper
- (see the FAQ):
- ss_vncviewer -verify ./cacert.crt hostname:0
-
- (this assumes the cacert.crt cert from -sslGenCA
- was safely copied to the VNC viewer machine where
- ss_vncviewer is run)
-
- Example using a name:
-
- x11vnc -sslGenCert server charlie
- x11vnc -ssl SAVE-charlie -display :0 ...
-
- Example for a client certificate (rarely used):
-
- x11vnc -sslGenCert client roger
- scp ~/.vnc/certs/clients/roger.pem somehost:.
- rm ~/.vnc/certs/clients/roger.pem
-
- x11vnc is then started with the option -sslverify
- ~/.vnc/certs/clients/roger.crt (or simply -sslverify
- roger), and on the viewer user on somehost could do
- for example:
-
- ss_vncviewer -mycert ./roger.pem hostname:0
-
- If you set the env. var REQ_ARGS='...' it will be
- passed to openssl req(1). A common use would be
- REQ_ARGS='-days 1095' to bump up the expiration date
- (3 years in this case).
-
--sslEncKey pem Utility to encrypt an existing PEM file with a
- passphrase you supply when prompted. For that key to be
- used (e.g. by x11vnc) the passphrase must be supplied
- each time.
-
- The "SAVE" notation described under -ssl applies as
- well. (precede this option with -ssldir [dir] to refer
- a directory besides the default ~/.vnc/certs)
-
- The openssl(1) program must be installed on the system
- and available in PATH. After the Key file is encrypted
- the x11vnc command exits; the VNC server is not run.
-
- Examples:
- x11vnc -sslEncKey /path/to/foo.pem
- x11vnc -sslEncKey SAVE
- x11vnc -sslEncKey SAVE-charlie
-
--sslCertInfo pem Prints out information about an existing PEM file.
- In addition the public certificate is also printed.
- The openssl(1) program must be in PATH. Basically the
- command "openssl x509 -text" is run on the pem.
-
- After the info is printed the x11vnc command exits;
- the VNC server is not run.
-
- The "SAVE" notation described under -ssl applies
- as well.
-
- Using "LIST" will give a list of all certs being
- managed (in the ~/.vnc/certs dir, use -ssldir to refer
- to another dir). "ALL" will print out the info for
- every managed key (this can be very long). Giving a
- client or server cert shortname will also try a lookup
- (e.g. -sslCertInfo charlie). Use "LISTL" or "LL"
- for a long (ls -l style) listing.
-
- Using "HASHON" will create subdirs [dir]/HASH and
- [dir]/HASH with OpenSSL hash filenames (e.g. 0d5fbbf1.0)
- symlinks pointing up to the corresponding *.crt file.
- ([dir] is ~/.vnc/certs or one given by -ssldir.)
- This is a useful way for other OpenSSL applications
- (e.g. stunnel) to access all of the certs without
- having to concatenate them. x11vnc will not use them
- unless you specifically reference them. "HASHOFF"
- removes these HASH subdirs.
-
- The LIST, LISTL, LL, ALL, HASHON, HASHOFF words can
- also be lowercase, e.g. "list".
-
--sslDelCert pem Prompts you to delete all .crt .pem .key .req files
- associated with [pem]. x11vnc then exits. "SAVE"
- and lookups as in -sslCertInfo apply as well.
-
--sslScripts Prints out both the 'genCA' and 'genCert' x11vnc
- openssl wrapper scripts for you to examine, modify, etc.
- The scripts are printed to stdout and then the x11vnc
- program exits.
-
-
--stunnel [pem] Use the stunnel(8) (stunnel.mirt.net) to provide an
- encrypted SSL tunnel between viewers and x11vnc.
-
- This external tunnel method was implemented prior to the
- integrated -ssl encryption described above. It still
- works well and avoids the requirement of linking with
- the OpenSSL libraries. This mode requires stunnel
- to be installed on the system and available via PATH
- (n.b. stunnel is often installed in sbin directories).
- Version 4.x of stunnel is assumed (but see -stunnel3
- below.)
-
- [pem] is optional, use "-stunnel /path/to/stunnel.pem"
- to specify a PEM certificate file to pass to stunnel.
- See the -ssl option for more info on certificate files.
-
- Whether or not your stunnel has its own certificate
- depends on your stunnel configuration; stunnel often
- generates one at install time. See your stunnel
- documentation for details. In any event, if you want to
- use this certificate you must supply the full path to it
- as [pem]. Note: the file may only be readable by root.
-
- [pem] may also be the special strings "TMP", "SAVE",
- and "SAVE..." as described in the -ssl option.
- If [pem] is not supplied, "SAVE" is assumed.
-
- Note that the VeNCrypt, ANONTLS, and "ANON" modes
- are not supported in -stunnel mode.
-
- stunnel is started up as a child process of x11vnc and
- any SSL connections stunnel receives are decrypted and
- sent to x11vnc over a local socket. The strings
- "The SSL VNC desktop is ..." and "SSLPORT=..."
- are printed out at startup to indicate this.
-
- The -localhost option is enforced by default to avoid
- people routing around the SSL channel. Use -env
- STUNNEL_DISABLE_LOCALHOST=1 to disable this security
- requirement.
-
- Set -env STUNNEL_DEBUG=1 for more debugging printout.
-
- Set -env STUNNEL_PROG=xxx to the full path of stunnel
- program you want to be used (e.g. /usr/bin/stunnel4).
-
- Set -env STUNNEL_LISTEN=xxx to the address of the
- network interface to listen on (the default is to listen
- on all interfaces), e.g. STUNNEL_LISTEN=192.168.1.100.
-
- A simple way to add IPv6 support is STUNNEL_LISTEN=::
-
- Your VNC viewer will also need to be able to connect
- via SSL. Unfortunately not too many do this. See the
- information about SSL viewers under the -ssl option.
- The x11vnc project's SSVNC is an option.
-
- Also, in the x11vnc distribution, patched TightVNC
- and UltraVNC Java applet jar files are provided in
- the classes/ssl directory that do SSL connections.
- Enable serving them with the -http, -http_ssl, or
- -httpdir (see the option descriptions for more info.)
-
- Note that for the Java viewer applet usage the
- "?PORT=xxxx" in the various URLs printed at startup
- will need to be supplied to the web browser to connect
- properly.
-
- Currently the automatic "single port" HTTPS mode of
- -ssl is not fully supported in -stunnel mode. However,
- it can be emulated via:
-
- % x11vnc -stunnel -http_ssl -http_oneport ...
-
- In general, it is also not too difficult to set up
- an stunnel or other SSL tunnel on the viewer side.
- A simple example on Unix using stunnel 3.x is:
-
- % stunnel -c -d localhost:5901 -r remotehost:5900
- % vncviewer localhost:1
-
- For Windows, stunnel has been ported to it and there
- are probably other such tools available. See the FAQ
- and SSVNC for more examples.
-
--stunnel3 [pem] Use version 3.x stunnel command line syntax instead of
- version 4.x. The -http/-httpdir Java applet serving
- is currently not available in this mode.
-
--enc cipher:keyfile Use symmetric encryption with cipher "cipher"
- and secret key data in "keyfile". If keyfile is
- pw=<string> then "string" is used as the key data.
-
- NOTE: It is recommended that you use SSL via the -ssl
- option instead of this option because SSL is well
- understood and takes great care to establish unique
- session keys and is more compatible with other software.
- Use this option if you do not want to deal with SSL
- certificates for authentication and do not want to
- use SSH but want some encryption for your VNC session.
- Or if you must interface with a symmetric key tunnel
- that you do not have control over.
-
- Note that this mode will NOT work with the UltraVNC DSM
- plugins because they alter the RFB protocol in addition
- to tunnelling with the symmetric cipher (an unfortunate
- choice of implementation...)
-
- cipher can be one of: arc4, aesv2, aes-cfb, blowfish,
- aes256, or 3des. See the OpenSSL documentation for
- more info. The keysize is 128 bits (except for aes256).
- Here is one way to make a keyfile with that many bits:
-
- dd if=/dev/random of=./my.key bs=16 count=1
-
- you will need to securely share this key with the other
- side of the VNC connection (See SSVNC for examples).
-
- Example: -enc blowfish:./my.key
- Example: -enc blowfish:pw=swordfish
-
- By default 16 bytes of random salt followed by 16 bytes
- of random initialization vector are sent at the very
- beginning of the stream. The other side must read these
- and initialize their cipher with them. These values
- make the session key unique (without them the security
- is minimal). Similarly, the other side must send us
- its random salt and IV with those same lengths.
-
- The salt and key data are combined to create a session
- key using an md5 hash as described in EVP_BytesToKey(3).
-
- The exact call is: EVP_BytesToKey(Cipher, EVP_md5(),
- salt, keydata, len, 1, keystr, NULL); where salt is
- the random data as described above, and keydata is the
- shared secret key data. keystr is the resulting session
- key. The cipher is then seeded with keystr and uses
- the random initialization vector as its first block.
-
- To modify the amount of random salt and initialization
- vector use cipher@n,m where n is the salt length and
- m the initialization vector length. E.g.
-
- -enc aes-cfb@8,16:./my.key
-
- It is not a good idea to set either one to zero,
- although you may be forced to if the other side of the
- tunnel is not under your control.
-
- To skip the salt and EVP_BytesToKey MD5 entirely (no
- hashing is done: the keydata is directly inserted into
- the cipher) specify "-1" for the salt, e.g.
-
- -enc blowfish@-1,16:./my.key
-
- The message digest can also be changed to something
- besides the default MD5. Use cipher@md+n,m where "md"
- can be one of sha, sha1, md5, or ripe. For example:
-
- -enc arc4@sha+8,16:./my.key
-
- The SSVNC vnc viewer project supplies a symmetric
- encryption tool named "ultravnc_dsm_helper" that can
- be used on the viewer side. For example:
-
- ssvncviewer exec='ultravnc_dsm_helper arc4 my.key 0 h:p'
-
- where h:p is the hostname and port of the x11vnc server.
- ultravnc_dsm_helper may also be used standalone to
- provide a symmetric encryption tunnel for any viewer
- or server (VNC or otherwise.) The cipher (1st arg)
- is basically the same syntax as we use above.
-
- Also see the 'Non-Ultra DSM' SSVNC option for the
- 'UltraVNC DSM Encryption Plugin' advanced option.
-
- For both ways of using the viewer, you can specify the
- salt,ivec sizes (in GUI or, e.g. arc4@8,16).
-
--https [port] Use a special, separate HTTPS port (-ssl and
- -stunnel modes only) for HTTPS Java viewer applet
- downloading. I.e. not 5900 and not 5800 (the defaults.)
-
- BACKGROUND: In -ssl mode, it turns out you can use the
- single VNC port (e.g. 5900) for both VNC and HTTPS
- connections. (HTTPS is used to retrieve a SSL-aware
- VncViewer.jar applet that is provided with x11vnc).
- Since both use SSL the implementation was extended to
- detect if HTTP traffic (i.e. GET) is taking place and
- handle it accordingly. The URL would be, e.g.:
-
- https://mymachine.org:5900/
-
- This is convenient for firewalls, etc, because only one
- port needs to be allowed in. However, this heuristic
- adds a few seconds delay to each connection and can be
- unreliable (especially if the user takes much time to
- ponder the Certificate dialogs in his browser, Java VM,
- or VNC Viewer applet. That's right 3 separate "Are
- you sure you want to connect?" dialogs!)
-
- END OF BACKGROUND.
-
- USAGE: So use the -https option to provide a separate,
- more reliable HTTPS port that x11vnc will listen on. If
- [port] is not provided (or is 0), one is autoselected.
- The URL to use is printed out at startup.
-
- The SSL Java applet directory is specified via the
- -httpdir option. If not supplied, -https will try
- to guess the directory as though the -http option
- was supplied.
-
--httpsredir [port] In -ssl mode with the Java applet retrieved via HTTPS,
- when the HTML file containing applet parameters
- ('index.vnc' or 'proxy.vnc') is sent do NOT set the
- applet PORT parameter to the actual VNC port but set it
- to "port" instead. If "port" is not supplied, then
- the port number is guessed from the Host: HTTP header.
-
- This is useful when an incoming TCP connection
- redirection is performed by a router/gateway/firewall
- from one port to an internal machine where x11vnc is
- listening on a different port. The Java applet needs to
- connect to the firewall/router port, not the VNC port
- on the internal workstation. For example, one could
- redir from mygateway.com:443 to workstation:5900.
-
- This spares the user from having to type in
- https://mygateway.com/?PORT=443 into their web
- browser. Note that port 443 is the default https port;
- other ports must be explicitly indicated, for example:
- https://mygateway.com:8000/?PORT=8000. To avoid having
- to include the PORT= in the browser URL, simply supply
- "-httpsredir" to x11vnc.
-
- This option does not work in -stunnel mode.
-
- More tricks: set the env var X11VNC_EXTRA_HTTPS_PARAMS
- to be extra URL parameters to use. This way you do
- not need to specify extra PARAMS in the index.vnc file.
- E.g. x11vnc -env X11VNC_EXTRA_HTTPS_PARAMS='?GET=1' ...
-
- If you do not want to expose the non-SSL HTTP port to
- the network (i.e. you just want the single VNC/HTTPS
- port, e.g. 5900, open for connections) then specify the
- option -env X11VNC_HTTP_LISTEN_LOCALHOST=1 This way
- the connection to the LibVNCServer httpd server will
- only be available on localhost (note that in -ssl mode,
- HTTPS requests are redirected from SSL to the non-SSL
- LibVNCServer HTTP server.)
-
--http_oneport For UN-encrypted connections mode (i.e. no -ssl,
- -stunnel, or -enc options), allow the Java VNC Viewer
- applet to be downloaded thru the VNC port via HTTP.
-
- That is to say, you can use a single port for Java
- applet viewer connections by using a URL in your web
- browser like this, for example:
-
- http://hostname:5900
-
- The regular, two-port mode, URL http://hostname:5800
- will continue to work as well.
-
- As mentioned above, this mode will NOT work with
- the -ssl, -stunnel, or -enc encryption options.
- Note that is it equivalent to '-enc none' (i.e. it
- uses the same detection mechanism as for HTTPS, but
- with no encryption.)
-
- HTTPS single-port is on by default in -ssl encrypted
- mode (and -enc too), so you only need -http_oneport
- when doing non-SSL encrypted connections.
-
- This mode could also be useful for SSH tunnels since
- it means only one port needs to be redirected.
-
- The -httpsredir option may also be useful for this
- mode when using an SSH tunnel as well as for router
- port redirections.
-
- Note that the -env X11VNC_HTTP_LISTEN_LOCALHOST=1
- option described above under -httpsredir applies for
- the LibVNCServer httpd server in all cases (ssl or not.)
-
--ssh user@host:disp Create a remote listening port on machine "host"
- via a SSH tunnel using the -R rport:localhost:lport
- method. lport will be the local x11vnc listening port,
- so a connection to rport (5900+disp) on "host"
- will reach x11vnc. E.g. fred@snoopy.com:0
-
- This could be useful if a firewall/router prevents
- incoming connections to the x11vnc machine, but
- the ssh machine "host" can be reached by the VNC
- viewer. "user@" is not needed unless the remote unix
- username differs from the current one.
-
- By default the remote sshd is usually configured to
- listen only on localhost for rport, so the viewer may
- need to ssh -L redir to "host" as well (See SSVNC to
- automate this). The sshd setting GatewayPorts enables
- listening on all interfaces for rport; viewers can
- reach it more easily.
-
- "disp" is the VNC display for the remote SSH side,
- e.g. 0 corresponds to port 5900, etc. If disp is
- greater than 200 the value is used as the port. Use a
- negative value to force a low port, e.g. host:-80 will
- use port 80.
-
- If ssh-agent is not active, then the ssh password needs
- to be entered in the terminal where x11vnc is running.
-
- By default the remote ssh will issue a 'sleep 300' to
- wait for the incoming connection for 5 mins. To modify
- this use user@host:disp+secs.
-
- If the remote SSH server is on a non-standard port
- (i.e. not 22) use user@host:port:disp+secs.
-
- Note that the ssh process MAY NOT be killed when
- x11vnc exits. It tries by looking at ps(1) output.
-
--usepw If no other password method was supplied on the command
- line, first look for ~/.vnc/passwd and if found use it
- with -rfbauth; next, look for ~/.vnc/passwdfile and
- use it with -passwdfile; otherwise, prompt the user
- for a password to create ~/.vnc/passwd and use it with
- the -rfbauth option. If none of these succeed x11vnc
- exits immediately.
-
--storepasswd pass file Store password "pass" as the VNC password in the
- file "file". Once the password is stored the
- program exits. Use the password via "-rfbauth file"
-
- If called with no arguments, "x11vnc -storepasswd",
- the user is prompted for a password and it is stored
- in the file ~/.vnc/passwd. Called with one argument,
- that will be the file to store the prompted password in.
-
--nopw Disable the big warning message when you use x11vnc
- without some sort of password.
-
--accept string Run a command (possibly to prompt the user at the
- X11 display) to decide whether an incoming client
- should be allowed to connect or not. "string" is
- an external command run via system(3) or some special
- cases described below. Be sure to quote "string"
- if it contains spaces, shell characters, etc. If the
- external command returns 0 the client is accepted,
- otherwise the client is rejected. See below for an
- extension to accept a client view-only.
-
- If x11vnc is running as root (say from inetd(8) or from
- display managers xdm(1), gdm(1), etc), think about the
- security implications carefully before supplying this
- option (likewise for the -gone option).
-
- Environment: The RFB_CLIENT_IP environment variable will
- be set to the incoming client IP number and the port
- in RFB_CLIENT_PORT (or -1 if unavailable). Similarly,
- RFB_SERVER_IP and RFB_SERVER_PORT (the x11vnc side
- of the connection), are set to allow identification
- of the tcp virtual circuit. The x11vnc process
- id will be in RFB_X11VNC_PID, a client id number in
- RFB_CLIENT_ID, and the number of other connected clients
- in RFB_CLIENT_COUNT. RFB_MODE will be "accept".
- RFB_STATE will be PROTOCOL_VERSION, SECURITY_TYPE,
- AUTHENTICATION, INITIALISATION, NORMAL, or UNKNOWN
- indicating up to which state the client has achieved.
- RFB_LOGIN_VIEWONLY will be 0, 1, or -1 (unknown).
- RFB_USERNAME, RFB_LOGIN_TIME, and RFB_CURRENT_TIME may
- also be set.
-
- If "string" is "popup" then a builtin popup window
- is used. The popup will time out after 120 seconds,
- use "popup:N" to modify the timeout to N seconds
- (use 0 for no timeout).
-
- In the case of "popup" and when the -unixpw option
- is specified, then a *second* window will be popped
- up after the user successfully logs in via his UNIX
- password. This time the user will be identified as
- UNIX:username@hostname, the "UNIX:" prefix indicates
- which user the viewer logged as via -unixpw. The first
- popup is only for whether to allow him to even *try*
- to login via unix password.
-
- If "string" is "xmessage" then an xmessage(1)
- invocation is used for the command. xmessage must be
- installed on the machine for this to work.
-
- Both "popup" and "xmessage" will present an option
- for accepting the client "View-Only" (the client
- can only watch). This option will not be presented if
- -viewonly has been specified, in which case the entire
- display is view only.
-
- If the user supplied command is prefixed with something
- like "yes:0,no:*,view:3 mycommand ..." then this
- associates the numerical command return code with
- the actions: accept, reject, and accept-view-only,
- respectively. Use "*" instead of a number to indicate
- the default action (in case the command returns an
- unexpected value). E.g. "no:*" is a good choice.
-
- Note that x11vnc blocks while the external command
- or popup is running (other clients may see no updates
- during this period). So a person sitting a the physical
- display is needed to respond to an popup prompt. (use
- a 2nd x11vnc if you lock yourself out).
-
- More -accept tricks: use "popupmouse" to only allow
- mouse clicks in the builtin popup to be recognized.
- Similarly use "popupkey" to only recognize
- keystroke responses. These are to help avoid the
- user accidentally accepting a client by typing or
- clicking. All 3 of the popup keywords can be followed
- by +N+M to supply a position for the popup window.
- The default is to center the popup window.
--afteraccept string As -accept, except to run a user supplied command after
- a client has been accepted and authenticated. RFB_MODE
- will be set to "afteraccept" and the other RFB_*
- variables are as in -accept. Unlike -accept, the
- command return code is not interpreted by x11vnc.
- Example: -afteraccept 'killall xlock &'
--gone string As -accept, except to run a user supplied command when
- a client goes away (disconnects). RFB_MODE will be
- set to "gone" and the other RFB_* variables are as
- in -accept. The "popup" actions apply as well.
- Unlike -accept, the command return code is not
- interpreted by x11vnc. Example: -gone 'xlock &'
-
--users list If x11vnc is started as root (say from inetd(8) or from
- display managers xdm(1), gdm(1), etc), then as soon
- as possible after connections to the X display are
- established try to switch to one of the users in the
- comma separated "list". If x11vnc is not running as
- root this option is ignored.
-
- Why use this option? In general it is not needed since
- x11vnc is already connected to the X display and can
- perform its primary functions. The option was added
- to make some of the *external* utility commands x11vnc
- occasionally runs work properly. In particular under
- GNOME and KDE to implement the "-solid color" feature
- external commands (gconftool-2 and dcop) unfortunately
- must be run as the user owning the desktop session.
- Since this option switches userid it also affects the
- userid used to run the processes for the -accept and
- -gone options. It also affects the ability to read
- files for options such as -connect, -allow, and -remap
- and also the ultra and tight filetransfer feature if
- enabled. Note that the -connect file is also sometimes
- written to.
-
- So be careful with this option since in some situations
- its use can decrease security.
-
- In general the switch to a user will only take place
- if the display can still be successfully opened as that
- user (this is primarily to try to guess the actual owner
- of the session). Example: "-users fred,wilma,betty".
- Note that a malicious local user "barney" by
- quickly using "xhost +" when logging in may possibly
- get the x11vnc process to switch to user "fred".
- What happens next?
-
- Under display managers it may be a long time before
- the switch succeeds (i.e. a user logs in). To instead
- make it switch immediately regardless if the display
- can be reopened prefix the username with the "+"
- character. E.g. "-users +bob" or "-users +nobody".
-
- The latter (i.e. switching immediately to user
- "nobody") is the only obvious use of the -users option
- that increases security.
-
- Use the following notation to associate a group with
- a user: user1.group1,user2.group2,... Note that
- initgroups(2) will still be called first to try to
- switch to ALL of a user's groups (primary and additional
- groups). Only if that fails or it is not available
- then the single group specified as above (or the user's
- primary group if not specified) is switched to with
- setgid(2). Use -env X11VNC_SINGLE_GROUP=1 to prevent
- trying initgroups(2) and only switch to the single
- group. This sort of setting is only really needed to
- make the ultra or tight filetransfer permissions work
- properly. This format applies to any comma separated lis
-t
- of users, even the special "=" modes described below.
-
- In -unixpw mode, if "-users unixpw=" is supplied
- then after a user authenticates himself via the
- -unixpw mechanism, x11vnc will try to switch to that
- user as though "-users +username" had been supplied.
- If you want to limit which users this will be done for,
- provide them as a comma separated list after "unixpw="
- Groups can also be specified as described above.
-
- Similarly, in -ssl mode, if "-users sslpeer=" is
- supplied then after an SSL client authenticates with his
- cert (the -sslverify option is required for this) x11vnc
- will extract a UNIX username from the "emailAddress"
- field (username@hostname.com) of the "Subject" of the
- x509 SSL cert and then try to switch to that user as
- though "-users +username" had been supplied. If you
- want to limit which users this will be done for, provide
- them as a comma separated list after "sslpeer=".
- Set the env. var X11VNC_SSLPEER_CN to use the Common
- Name (normally a hostname) instead of the Email field.
-
- NOTE: for sslpeer= mode the x11vnc administrator must
- take care that any client certs he adds to -sslverify
- have the intended UNIX username in the "emailAddress"
- field of the cert. Otherwise a user may be able to
- log in as another. This command can be of use in
- checking: "openssl x509 -text -in file.crt", see the
- "Subject:" line. Also, along with the normal RFB_*
- env. vars. (see -accept) passed to external cmd=
- commands, RFB_SSL_CLIENT_CERT will be set to the
- client's x509 certificate string.
-
- The sslpeer= mode can aid finding X sessions via the
- FINDDISPLAY and FINDCREATEDISPLAY mechanisms.
-
- To immediately switch to a user *before* connections
- to the X display are made or any files opened use the
- "=" character: "-users =bob". That user needs to
- be able to open the X display and any files of course.
-
- The special user "guess=" means to examine the utmpx
- database (see who(1)) looking for a user attached to
- the display number (from DISPLAY or -display option)
- and try him/her. To limit the list of guesses, use:
- "-users guess=bob,betty".
-
- Even more sinister is the special user "lurk="
- that means to try to guess the DISPLAY from the utmpx
- login database as well. So it "lurks" waiting for
- anyone to log into an X session and then connects to it.
- Specify a list of users after the = to limit which users
- will be tried. To enable a different searching mode, if
- the first user in the list is something like ":0" or
- ":0-2" that indicates a range of DISPLAY numbers that
- will be tried (regardless of whether they are in the
- utmpx database) for all users that are logged in. Also
- see the "-display WAIT:..." functionality. Examples:
- "-users lurk=" and also "-users lurk=:0-1,bob,mary"
-
- Be especially careful using the "guess=" and "lurk="
- modes. They are not recommended for use on machines
- with untrustworthy local users.
-
--noshm Do not use the MIT-SHM extension for the polling.
- Remote displays can be polled this way: be careful this
- can use large amounts of network bandwidth. This is
- also of use if the local machine has a limited number
- of shm segments and -onetile is not sufficient.
--flipbyteorder Sometimes needed if remotely polled host has different
- endianness. Ignored unless -noshm is set.
--onetile Do not use the new copy_tiles() framebuffer mechanism,
- just use 1 shm tile for polling. Limits shm segments
- used to 3.
-
- To disable any automatic shm reduction set the
- env. var. X11VNC_NO_LIMIT_SHM.
-
--solid [color] To improve performance, when VNC clients are connected
- try to change the desktop background to a solid color.
- The [color] is optional: the default color is "cyan4".
- For a different one specify the X color (rgb.txt name,
- e.g. "darkblue" or numerical "#RRGGBB").
-
- Currently this option only works on GNOME, KDE, CDE,
- XFCE, and classic X (i.e. with the background image
- on the root window). The "gconftool-2", "dcop"
- and "xfconf-query" external commands are run for
- GNOME, KDE, and XFCE respectively. This also works
- on native MacOSX. (There is no color selection for
- MacOSX or XFCE.) Other desktops won't work, (send
- us the corresponding commands if you find them).
- If x11vnc is running as root (inetd(8) or gdm(1)),
- the -users option may be needed for GNOME, KDE, XFCE.
- If x11vnc guesses your desktop incorrectly, you can
- force it by prefixing color with "gnome:", "kde:",
- "cde:", "xfce:", or "root:".
-
- Update: -solid no longer works on KDE4.
-
- This mode works in a limited way on the Mac OS X Console
- with one color ('kelp') using the screensaver writing
- to the background. Look in "~/Library/Screen Savers"
- for VncSolidColor.png to change the color.
-
--blackout string Black out rectangles on the screen. "string" is a
- comma separated list of WxH+X+Y type geometries for
- each rectangle. If one of the items on the list is the
- string "noptr" the mouse pointer will not be allowed
- to go into a blacked out region.
--xinerama If your screen is composed of multiple monitors
--noxinerama glued together via XINERAMA, and that screen is
- not a rectangle this option will try to guess the
- areas to black out (if your system has libXinerama).
- default: -xinerama
-
- In general, we have noticed on XINERAMA displays you may
- need to use the "-xwarppointer" option if the mouse
- pointer misbehaves and it is enabled by default. Use
- "-noxwarppointer" if you do not want this.
-
--xtrap Use the DEC-XTRAP extension for keystroke and mouse
- input insertion. For use on legacy systems, e.g. X11R5,
- running an incomplete or missing XTEST extension.
- By default DEC-XTRAP will be used if XTEST server grab
- control is missing, use -xtrap to do the keystroke and
- mouse insertion via DEC-XTRAP as well.
-
--xrandr [mode] If the display supports the XRANDR (X Resize, Rotate
- and Reflection) extension, and you expect XRANDR events
- to occur to the display while x11vnc is running, this
- options indicates x11vnc should try to respond to
- them (as opposed to simply crashing by assuming the
- old screen size). See the xrandr(1) manpage and run
- 'xrandr -q' for more info. [mode] is optional and
- described below.
-
- Since watching for XRANDR events and trapping errors
- increases polling overhead, only use this option if
- XRANDR changes are expected. For example on a rotatable
- screen PDA or laptop, or using a XRANDR-aware Desktop
- where you resize often. It is best to be viewing with a
- vncviewer that supports the NewFBSize encoding, since it
- knows how to react to screen size changes. Otherwise,
- LibVNCServer tries to do so something reasonable for
- viewers that cannot do this (portions of the screen
- may be clipped, unused, etc).
-
- Note: the default now is to check for XRANDR events, but
- do not trap every X call that may fail due to resize.
- If a resize event is received, the full -xrandr mode
- is enabled. To disable even checking for events supply:
- -noxrandr.
-
- "mode" defaults to "resize", which means create a
- new, resized, framebuffer and hope all viewers can cope
- with the change. "newfbsize" means first disconnect
- all viewers that do not support the NewFBSize VNC
- encoding, and then resize the framebuffer. "exit"
- means disconnect all viewer clients, and then terminate
- x11vnc.
-
--rotate string Rotate and/or flip the framebuffer view exported by VNC.
- This transformation is independent of XRANDR and is
- done in software in main memory and so may be slower.
- This mode could be useful on a handheld with portrait or
- landscape modes that do not correspond to the scanline
- order of the actual framebuffer. "string" can be:
-
- x flip along x-axis
- y flip along y-axis
- xy flip along x- and y-axes
- +90 rotate 90 degrees clockwise
- -90 rotate 90 degrees counter-clockwise
- +90x rotate 90 degrees CW, then flip along x
- +90y rotate 90 degrees CW, then flip along y
-
- these give all possible rotations and reflections.
-
- Aliases: same as xy: yx, +180, -180, 180
- same as -90: +270, 270
- same as +90: 90, (ditto for 90x, 90y)
-
- Like -scale, this transformation is applied at the very
- end of any chain of framebuffer transformations and so
- any options with geometries, e.g. -blackout, -clip, etc.
- are relative to the original X (or -rawfb) framebuffer,
- not the final one sent to VNC viewers.
-
- If you do not want the cursor shape to be rotated
- prefix "string" with "nc:", e.g. "nc:+90",
- "nc:xy", etc.
-
--padgeom WxH Whenever a new vncviewer connects, the framebuffer is
- replaced with a fake, solid black one of geometry WxH.
- Shortly afterwards the framebuffer is replaced with the
- real one. This is intended for use with vncviewers
- that do not support NewFBSize and one wants to make
- sure the initial viewer geometry will be big enough
- to handle all subsequent resizes (e.g. under -xrandr,
- -remote id:windowid, rescaling, etc.)
-
- In -unixpw mode this sets the size of the login screen.
- Use "once:WxH" it ignore padgeom after the login
- screen is set up.
-
--o logfile Write stderr messages to file "logfile" instead of to
- the terminal. Same as "-logfile file". To append
- to the file use "-oa file" or "-logappend file".
- If "logfile" contains the string "%VNCDISPLAY"
- it is expanded to the vnc display (the name may need
- to be guessed at.) "%HOME" works too.
-
--flag file Write the "PORT=NNNN" (e.g. PORT=5900) string to
- "file" in addition to stdout. This option could be
- useful by wrapper script to detect when x11vnc is ready.
-
--rmflag file Remove "file" at exit to signal when x11vnc is done.
- The file is created at startup if it does not already
- exist or if "file" is prefixed with "create:".
- If the file is created, the x11vnc PID is placed in
- the file. Otherwise the files contents is not changed.
- Use prefix "nocreate:" to prevent creation.
-
--rc filename Use "filename" instead of $HOME/.x11vncrc for rc file.
--norc Do not process any .x11vncrc file for options.
-
--env VAR=VALUE Set the environment variable 'VAR' to value 'VALUE'
- at x11vnc startup. This is a convenience utility to
- avoid shell script wrappers, etc. to set the env. var.
- You may specify as many of these as needed on the
- command line.
--prog /path/to/x11vnc Set the full path to the x11vnc program for cases when
- it cannot be determined from argv[0] (e.g. tcpd/inetd)
-
--h, -help Print this help text.
--?, -opts Only list the x11vnc options.
--V, -version Print program version and last modification date.
--license Print out license information. Same as -copying and
- -warranty.
-
--dbg Instead of exiting after cleaning up, run a simple
- "debug crash shell" when fatal errors are trapped.
-
--q, -quiet Be quiet by printing less informational output to
- stderr. (use -noquiet to undo an earlier -quiet.)
-
- The -quiet option does not eliminate all informational
- output, it only reduces it. It is ignored in most
- auxiliary usage modes, e.g. -storepasswd. To eliminate
- all output use: 2>/dev/null 1>&2, etc.
-
--v, -verbose Print out more information to stderr.
-
--bg Go into the background after screen setup. Messages to
- stderr are lost unless -o logfile is used. Something
- like this could be useful in a script:
- port=`ssh -t $host "x11vnc -display :0 -bg" | grep PORT
-`
- port=`echo "$port" | sed -e 's/PORT=//'`
- port=`expr $port - 5900`
- vncviewer $host:$port
-
--modtweak Option -modtweak automatically tries to adjust the AltGr
--nomodtweak and Shift modifiers for differing language keyboards
- between client and host. Otherwise, only a single key
- press/release of a Keycode is simulated (i.e. ignoring
- the state of the modifiers: this usually works for
- identical keyboards). Also useful in resolving cases
- where a Keysym is bound to multiple keys (e.g. "<" + ">"
- and "," + "<" keys). Default: -modtweak
-
- If you are having trouble with with keys and -xkb or
- -noxkb, and similar things don't help, try -nomodtweak.
-
- On some HP-UX systems it is been noted that they have
- an odd keymapping where a single keycode will have a
- keysym, e.g. "#", up to three times. You can check
- via "xmodmap -pk" or the -dk option. The failure
- is when you try to type "#" it yields "3". If you
- see this problem try setting the environment variable
- MODTWEAK_LOWEST=1 to see if it helps.
-
--xkb When in modtweak mode, use the XKEYBOARD extension (if
--noxkb the X display supports it) to do the modifier tweaking.
- This is powerful and should be tried if there are still
- keymapping problems when using -modtweak by itself.
- The default is to check whether some common keysyms,
- e.g. !, @, [, are only accessible via -xkb mode and if
- so then automatically enable the mode. To disable this
- automatic detection use -noxkb.
-
- When -xkb mode is active you can set these env. vars.
- They apply only when there is ambiguity as to which
- key to choose (i.e the mapping is not one-to-one).
- NOKEYHINTS=1: for up ascii keystrokes do not use score
- hints saved when the key was pressed down. NOANYDOWN=1:
- for up keystrokes do not resort to searching through
- keys that are currently pressed down. KEYSDOWN=N:
- remember the last N keys press down for tie-breaking
- when an up keystroke comes in.
-
--capslock When in -modtweak (the default) or -xkb mode,
- if a keysym in the range A-Z comes in check the X
- server to see if the Caps_Lock is set. If it is do
- not artificially press Shift to generate the keysym.
- This will enable the CapsLock key to behave correctly
- in some circumstances: namely *both* the VNC viewer
- machine and the x11vnc X server are in the CapsLock
- on state. If one side has CapsLock on and the other
- off and the keyboard is not behaving as you think it
- should you should correct the CapsLock states (hint:
- pressing CapsLock inside and outside of the viewer can
- help toggle them both to the correct state). However,
- for best results do not use this option, but rather
- *only* enable CapsLock on the VNC viewer side (i.e. by
- pressing CapsLock outside of the viewer window, also
- -skip_lockkeys below). Also try -nomodtweak for a
- possible workaround.
-
--skip_lockkeys Have x11vnc ignore all Caps_Lock, Shift_Lock, Num_Lock,
--noskip_lockkeys Scroll_Lock keysyms received from viewers. The idea is
- you press Caps_Lock on the VNC Viewer side but that does
- not change the lock state in the x11vnc-side X server.
- Nevertheless your capitalized letters come in over
- the wire and are applied correctly to the x11vnc-side
- X server. Note this mode probably won't do what you
- want in -nomodtweak mode. Also, a kludge for KP_n
- digits is always done in this mode: they are mapped to
- regular digit keysyms. See also -capslock above.
- The default is -noskip_lockkeys.
-
--skip_keycodes string Ignore the comma separated list of decimal keycodes.
- Perhaps these are keycodes not on your keyboard but
- your X server thinks exist. Currently only applies
- to -xkb mode. Use this option to help x11vnc in the
- reverse problem it tries to solve: Keysym -> Keycode(s)
- when ambiguities exist (more than one Keycode per
- Keysym). Run 'xmodmap -pk' to see your keymapping.
- Example: "-skip_keycodes 94,114"
--sloppy_keys Experimental option that tries to correct some
- "sloppy" key behavior. E.g. if at the viewer you
- press Shift+Key but then release the Shift before
- Key that could give rise to extra unwanted characters
- (usually only between keyboards of different languages).
- Only use this option if you observe problems with
- some keystrokes.
--skip_dups Some VNC viewers send impossible repeated key events,
--noskip_dups e.g. key-down, key-down, key-up, key-up all for the same
- key, or 20 downs in a row for the same modifier key!
- Setting -skip_dups means to skip these duplicates and
- just process the first event. Note: some VNC viewers
- assume they can send down's without the corresponding
- up's and so you should not set this option for
- these viewers (symptom: some keys do not autorepeat)
- Default: -noskip_dups
--add_keysyms If a Keysym is received from a VNC viewer and that
--noadd_keysyms Keysym does not exist in the X server, then add the
- Keysym to the X server's keyboard mapping on an unused
- key. Added Keysyms will be removed periodically and
- also when x11vnc exits. Default: -add_keysyms
--clear_mods At startup and exit clear the modifier keys by sending
- KeyRelease for each one. The Lock modifiers are skipped.
- Used to clear the state if the display was accidentally
- left with any pressed down.
--clear_keys As -clear_mods, except try to release ANY pressed key.
- Note that this option and -clear_mods can interfere
- with a person typing at the physical keyboard.
--clear_all As -clear_keys, except try to release any CapsLock,
- NumLock, etc. locks as well.
-
--remap string Read Keysym remappings from file named "string".
- Format is one pair of Keysyms per line (can be name
- or hex value) separated by a space. If no file named
- "string" exists, it is instead interpreted as this
- form: key1-key2,key3-key4,... See <X11/keysymdef.h>
- header file for a list of Keysym names, or use xev(1).
-
- To map a key to a button click, use the fake Keysyms
- "Button1", ..., etc. E.g: "-remap Super_R-Button2"
- (useful for pasting on a laptop)
-
- I use these if the machine I am viewing from does not
- have a scrollwheel or I don't like using the one it has:
-
- -remap Super_R-Button4,Menu-Button5
- -remap KP_Add-Button4,KP_Enter-Button5
-
- the former would be used on a PC, the latter on a
- MacBook. This way those little used keys can be used
- to generate bigger hops than the Up and Down arrows
- provide. One can scroll through text or web pages more
- quickly this way (especially if x11vnc scroll detection
- is active.)
-
- Use Button44, Button12, etc. for multiple clicks.
-
- To disable a keysym (i.e. make it so it will not be
- injected), remap it to "NoSymbol" or "None".
-
- Dead keys: "dead" (or silent, mute) keys are keys that
- do not produce a character but must be followed by a 2nd
- keystroke. This is often used for accenting characters,
- e.g. to put "`" on top of "a" by pressing the dead
- key and then "a". Note that this interpretation
- is not part of core X11, it is up to the toolkit or
- application to decide how to react to the sequence.
- The X11 names for these keysyms are "dead_grave",
- "dead_acute", etc. However some VNC viewers send the
- keysyms "grave", "acute" instead thereby disabling
- the accenting. To work around this -remap can be used.
- For example "-remap grave-dead_grave,acute-dead_acute"
- As a convenience, "-remap DEAD" applies these remaps:
-
- g grave-dead_grave
- a acute-dead_acute
- c asciicircum-dead_circumflex
- t asciitilde-dead_tilde
- m macron-dead_macron
- b breve-dead_breve
- D abovedot-dead_abovedot
- d diaeresis-dead_diaeresis
- o degree-dead_abovering
- A doubleacute-dead_doubleacute
- r caron-dead_caron
- e cedilla-dead_cedilla
-
- If you just want a subset use the first letter
- label, e.g. "-remap DEAD=ga" to get the first two.
- Additional remaps may also be supplied via commas,
- e.g. "-remap DEAD=ga,Super_R-Button2". Finally,
- "DEAD=missing" means to apply all of the above as
- long as the left hand member is not already in the
- X11 keymap.
-
--norepeat Option -norepeat disables X server key auto repeat when
--repeat VNC clients are connected and VNC keyboard input is
- not idle for more than 5 minutes. This works around a
- repeating keystrokes bug (triggered by long processing
- delays between key down and key up client events:
- either from large screen changes or high latency).
- Default: -norepeat
-
- You can set the env. var. X11VNC_IDLE_TIMEOUT to the
- number of idle seconds you want (5min = 300secs).
-
- Note: your VNC viewer side will likely do autorepeating,
- so this is no loss unless someone is simultaneously at
- the real X display.
-
- Use "-norepeat N" to set how many times norepeat will
- be reset if something else (e.g. X session manager)
- undoes it. The default is 2. Use a negative value
- for unlimited resets.
-
--nofb Ignore video framebuffer: only process keyboard and
- pointer. Intended for use with Win2VNC and x2vnc
- dual-monitor setups.
--nobell Do not watch for XBell events. (no beeps will be heard)
- Note: XBell monitoring requires the XKEYBOARD extension.
--nosel Do not manage exchange of X selection/cutbuffer between
- VNC viewers and the X server at all.
--noprimary Do not poll the PRIMARY selection for changes to send
- back to clients. (PRIMARY is still set on received
- changes, however).
--nosetprimary Do not set the PRIMARY selection for changes received
- from VNC clients.
--noclipboard Do not poll the CLIPBOARD selection for changes to send
- back to clients. (CLIPBOARD is still set on received
- changes, however).
--nosetclipboard Do not set the CLIPBOARD selection for changes
- received from VNC clients.
--seldir string If direction string is "send", only send the selection
- to viewers, and if it is "recv" only receive it from
- viewers. To work around apps setting the selection
- too frequently and messing up the other end. You can
- actually supply a comma separated list of directions,
- including "debug" to turn on debugging output.
-
--cursor [mode] Sets how the pointer cursor shape (little icon at the
--nocursor mouse pointer) should be handled. The "mode" string
- is optional and is described below. The default
- is to show some sort of cursor shape(s). How this
- is done depends on the VNC viewer and the X server.
- Use -nocursor to disable cursor shapes completely.
-
- Some VNC viewers support the TightVNC CursorPosUpdates
- and CursorShapeUpdates extensions (cuts down on
- network traffic by not having to send the cursor image
- every time the pointer is moved), in which case these
- extensions are used (see -nocursorshape and -nocursorpos
- below to disable). For other viewers the cursor shape
- is written directly to the framebuffer every time the
- pointer is moved or changed and gets sent along with
- the other framebuffer updates. In this case, there
- will be some lag between the vnc viewer pointer and
- the remote cursor position.
-
- If the X display supports retrieving the cursor shape
- information from the X server, then the default is
- to use that mode. On Solaris this can be done with
- the SUN_OVL extension using -overlay (see also the
- -overlay_nocursor option). A similar overlay scheme
- is used on IRIX. Xorg (e.g. Linux) and recent Solaris
- Xsun servers support the XFIXES extension to retrieve
- the exact cursor shape from the X server. If XFIXES
- is present it is preferred over Overlay and is used by
- default (see -noxfixes below). This can be disabled
- with -nocursor, and also some values of the "mode"
- option below.
-
- Note that under XFIXES cursors with transparency (alpha
- channel) will usually not be exactly represented and one
- may find Overlay preferable. See also the -alphacut
- and -alphafrac options below as fudge factors to try
- to improve the situation for cursors with transparency
- for a given theme.
-
- The "mode" string can be used to fine-tune the
- displaying of cursor shapes. It can be used the
- following ways:
-
- "-cursor arrow" - just show the standard arrow
- nothing more or nothing less.
-
- "-cursor none" - same as "-nocursor"
-
- "-cursor X" - when the cursor appears to be on the
- root window, draw the familiar X shape. Some desktops
- such as GNOME cover up the root window completely,
- and so this will not work, try "X1", etc, to try to
- shift the tree depth. On high latency links or slow
- machines there will be a time lag between expected and
- the actual cursor shape.
-
- "-cursor some" - like "X" but use additional
- heuristics to try to guess if the window should have
- a windowmanager-like resizer cursor or a text input
- I-beam cursor. This is a complete hack, but may be
- useful in some situations because it provides a little
- more feedback about the cursor shape.
-
- "-cursor most" - try to show as many cursors as
- possible. Often this will only be the same as "some"
- unless the display has overlay visuals or XFIXES
- extensions available. On Solaris and IRIX if XFIXES
- is not available, -overlay mode will be attempted.
-
--cursor_drag Show cursor shape changes even when the mouse is being
- dragged with a mouse button down. This is useful if you
- want to be able to see Drag-and-Drop cursor icons, etc.
-
--arrow n Choose an alternate "arrow" cursor from a set of
- some common ones. n can be 1 to 6. Default is: 1
- Ignored when in XFIXES cursor-grabbing mode.
-
--noxfixes Do not use the XFIXES extension to draw the exact cursor
- shape even if it is available.
-
- Note: To work around a crash in Xorg 1.5 and later
- some people needed to use -noxfixes. The Xorg crash
- occurred right after a Display Manager (e.g. GDM) login.
- Starting with x11vnc 0.9.9 it tries to automatically
- avoid using XFIXES until it is sure a window manager
- is running. See the -reopen option for more info and
- how to use X11VNC_AVOID_WINDOWS=never to disable it.
-
--alphacut n When using the XFIXES extension for the cursor shape,
- cursors with transparency will not usually be displayed
- exactly (but opaque ones will). This option sets n as
- a cutoff for cursors that have transparency ("alpha
- channel" with values ranging from 0 to 255) Any cursor
- pixel with alpha value less than n becomes completely
- transparent. Otherwise the pixel is completely opaque.
- Default 240
-
--alphafrac fraction With the threshold in -alphacut some cursors will become
- almost completely transparent because their alpha values
- are not high enough. For those cursors adjust the
- alpha threshold until fraction of the non-zero alpha
- channel pixels become opaque. Default 0.33
--alpharemove By default, XFIXES cursors pixels with transparency have
- the alpha factor multiplied into the RGB color values
- (i.e. that corresponding to blending the cursor with a
- black background). Specify this option to remove the
- alpha factor. (useful for light colored semi-transparent
- cursors).
--noalphablend In XFIXES mode do not send cursor alpha channel data
- to LibVNCServer. The default is to send it. The
- alphablend effect will only be visible in -nocursorshape
- mode or for clients with cursorshapeupdates turned
- off. (However there is a hack for 32bpp with depth 24,
- it uses the extra 8 bits to store cursor transparency
- for use with a hacked vncviewer that applies the
- transparency locally. See the FAQ for more info).
-
--nocursorshape Do not use the TightVNC CursorShapeUpdates extension
- even if clients support it. See -cursor above.
--cursorpos Option -cursorpos enables sending the X cursor position
--nocursorpos back to all vnc clients that support the TightVNC
- CursorPosUpdates extension. Other clients will be able
- to see the pointer motions. Default: -cursorpos
--xwarppointer Move the pointer with XWarpPointer(3X) instead of
--noxwarppointer the XTEST extension. Use this as a workaround
- if the pointer motion behaves incorrectly, e.g.
- on touchscreens or other non-standard setups.
-
- It is also sometimes needed on XINERAMA displays and is
- enabled by default if XINERAMA is found to be active.
- To prevent this, use -noxwarppointer.
-
--always_inject Even if there is no displacement (dx = dy = 0) for a
- VNC mouse event force the pointer to the indicated x,y
- position anyway. Recent (2009) gui toolkits (gnome)
- have problems with x11vnc's original mouse input
- injection method. So x11vnc's mouse input injection
- method has been modified. To regain the OLD behavior
- use this option: -always_inject. Then x11vnc will
- always force positioning the mouse to the x,y position
- even if that position has not changed since the previous
- VNC input event.
-
- The first place this problem was noticed was in gnome
- terminal: if you pressed and released mouse button 3, a
- menu was posted and then its first element 'New Terminal
- Window' was activated. This was because x11vnc injected
- the mouse position twice: once on ButtonPress and again
- on ButtonRelease. The toolkit interpreted the 2nd one
- as mouse motion even though the mouse hadn't moved.
- So now by default x11vnc tries to avoid injecting the
- 2nd one.
-
- Note that with the new default x11vnc will be oblivious
- to applications moving the pointer (warping) or the
- user at the physical display moving it. So it might,
- e.g., inject ButtonRelease at the wrong position.
- If this (or similar scenarios) causes problems in your
- environment, specify -always_inject for the old method.
-
--buttonmap string String to remap mouse buttons. Format: IJK-LMN, this
- maps buttons I -> L, etc., e.g. -buttonmap 13-31
-
- Button presses can also be mapped to keystrokes: replace
- a button digit on the right of the dash with :<sym>:
- or :<sym1>+<sym2>: etc. for multiple keys. For example,
- if the viewing machine has a mouse-wheel (buttons 4 5)
- but the x11vnc side does not, these will do scrolls:
- -buttonmap 12345-123:Prior::Next:
- -buttonmap 12345-123:Up+Up+Up::Down+Down+Down:
-
- See <X11/keysymdef.h> header file for a list of Keysyms,
- or use the xev(1) program. Note: mapping of button
- clicks to Keysyms may not work if -modtweak or -xkb is
- needed for the Keysym.
-
- If you include a modifier like "Shift_L" the
- modifier's up/down state is toggled, e.g. to send
- "The" use :Shift_L+t+Shift_L+h+e: (the 1st one is
- shift down and the 2nd one is shift up). (note: the
- initial state of the modifier is ignored and not reset)
- To include button events use "Button1", ... etc.
-
- -buttonmap currently does not work on MacOSX console
- or in -rawfb mode.
-
- Workaround: use -buttonmap IJ...-LM...=n to limit the
- number of mouse buttons to n, e.g. 123-123=3. This will
- prevent x11vnc from crashing if the X server reports
- there are 5 buttons (4/5 scroll wheel), but there are
- only really 3.
-
--nodragging Do not update the display during mouse dragging events
- (mouse button held down). Greatly improves response on
- slow setups, but you lose all visual feedback for drags,
- text selection, and some menu traversals. It overrides
- any -pointer_mode setting.
-
--ncache n Client-side caching scheme. Framebuffer memory "n"
- (an integer) times that of the full display is allocated
- below the actual framebuffer to cache screen contents
- for rapid retrieval. So a W x H frambuffer is expanded
- to a W x (n+1)*H one. Use 0 to disable.
-
- The "n" is actually optional, the default is 10.
-
- For this and the other -ncache* options below you can
- abbreviate "-ncache" with "-nc". Also, "-nonc"
- is the same as "-ncache 0"
-
- This is an experimental option, currently implemented in
- an awkward way in that in the VNC Viewer you can see the
- pixel cache contents if you scroll down, etc. So you
- will have to set things up so you can't see that region.
- If this method is successful, the changes required for
- clients to do this less awkwardly will be investigated.
-
- The SSVNC viewer does a good job at automatically hiding
- the pixel cache region. Or use SSVNC's -ycrop option
- to explicitly hide the region.
-
- Note that this mode consumes a huge amount of memory,
- both on the x11vnc server side and on the VNC Viewer
- side. If n=2 then the amount of RAM used is roughly
- tripled for both x11vnc and the VNC Viewer. As a rule
- of thumb, note that 1280x1024 at depth 24 is about 5MB
- of pixel data.
-
- For reasonable response when cycling through 4 to 6
- large (e.g. web browser) windows a value n of 6 to 12
- is recommended. (that's right: ~10X more memory...)
-
- Because of the way window backingstore and saveunders
- are implemented, n must be even. It will be incremented
- by 1 if it is not.
-
- This mode also works for native MacOS X, but may not
- be as effective as the X version. This is due to a
- number of things, one is the drop-shadow compositing
- that leaves extra areas that need to be repaired (see
- -ncache_pad). Another is the window iconification
- animations need to be avoided (see -macicontime).
- It appears the that the 'Scale' animation mode gives
- better results than the 'Genie' one. Also, window event
- detection not as accurate as the X version.
-
--ncache_cr In -ncache mode, try to do copyrect opaque window
- moves/drags instead of wireframes (this can induce
- painting errors). The wireframe will still be used when
- moving a window whose save-unders has not yet been set
- or has been invalidated.
-
- Some VNC Viewers provide better response than others
- with this option. On Unix, realvnc viewer gives
- smoother drags than tightvnc viewer. Response may also
- be choppy if the server side machine is too slow.
-
- Sometimes on very slow modem connections, this actually
- gives an improvement because no pixel data at all
- (not even the box animation) is sent during the drag.
-
--ncache_no_moveraise In -ncache mode, do not assume that moving a window
- will cause the window manager to raise it to the top
- of the stack. The default is to assume it does, and
- so at the beginning of any wireframe, etc, window moves
- the window will be pushed to top in the VNC viewer.
-
--ncache_no_dtchange In -ncache mode, do not try to guess when the desktop
- (viewport) changes to another one (i.e. another
- workarea). The default is to try to guess and when
- detected try to make the transistion more smoothly.
-
--ncache_no_rootpixmap In -ncache mode, do not try to snapshot the desktop
- background to use in guessing or reconstructing window
- save-unders.
-
--ncache_keep_anims In -ncache mode, do not try to disable window
- manager animations and other effects (that usually
- degrade ncache performance or cause painting errors).
- The default is to try to disable them on KDE (but not
- GNOME) when VNC clients are connected.
-
- For other window managers or desktops that provide
- animations, effects, compositing, translucency,
- etc. that interfere with the -ncache method you will
- have to disable them manually.
-
--ncache_old_wm In -ncache mode, enable some heuristics for old style
- window managers such as fvwm and twm.
-
--ncache_pad n In -ncache mode, pad each window with n pixels for the
- caching rectangles. This can be used to try to improve
- the situation with dropshadows or other compositing
- (e.g. MacOS X window manager), although it could make
- things worse. The default is 0 on Unix and 24 on
- MacOS X.
--debug_ncache Turn on debugging and profiling output under -ncache.
-
--wireframe [str] Try to detect window moves or resizes when a mouse
--nowireframe button is held down and show a wireframe instead of
- the full opaque window. This is based completely on
- heuristics and may not always work: it depends on your
- window manager and even how you move things around.
- See -pointer_mode below for discussion of the "bogging
- down" problem this tries to avoid.
- Default: -wireframe
-
- Shorter aliases: -wf [str] and -nowf
-
- The value "str" is optional and, of course, is
- packed with many tunable parameters for this scheme:
-
- Format: shade,linewidth,percent,T+B+L+R,mod,t1+t2+t3+t4
- Default: 0xff,2,0,32+8+8+8,all,0.15+0.30+5.0+0.125
-
- If you leave nothing between commas: ",," the default
- value is used. If you don't specify enough commas,
- the trailing parameters are set to their defaults.
-
- "shade" indicate the "color" for the wireframe,
- usually a greyscale: 0-255, however for 16 and 32bpp you
- can specify an rgb.txt X color (e.g. "dodgerblue") or
- a value > 255 is treated as RGB (e.g. red is 0xff0000).
- "linewidth" sets the width of the wireframe in pixels.
- "percent" indicates to not apply the wireframe scheme
- to windows with area less than this percent of the
- full screen.
-
- "T+B+L+R" indicates four integers for how close in
- pixels the pointer has to be from the Top, Bottom, Left,
- or Right edges of the window to consider wireframing.
- This is a speedup to quickly exclude a window from being
- wireframed: set them all to zero to not try the speedup
- (scrolling and selecting text will likely be slower).
-
- "mod" specifies if a button down event in the
- interior of the window with a modifier key (Alt, Shift,
- etc.) down should indicate a wireframe opportunity.
- It can be "0" or "none" to skip it, "1" or "all"
- to apply it to any modifier, or "Shift", "Alt",
- "Control", "Meta", "Super", or "Hyper" to only
- apply for that type of modifier key.
-
- "t1+t2+t3+t4" specify four floating point times in
- seconds: t1 is how long to wait for the pointer to move,
- t2 is how long to wait for the window to start moving
- or being resized (for some window managers this can be
- rather long), t3 is how long to keep a wireframe moving
- before repainting the window. t4 is the minimum time
- between sending wireframe "animations". If a slow
- link is detected, these values may be automatically
- changed to something better for a slow link.
-
--nowireframelocal By default, mouse motion and button presses of a
- user sitting at the LOCAL display are monitored for
- wireframing opportunities (so that the changes will be
- sent efficiently to the VNC clients). Use this option
- to disable this behavior.
-
--wirecopyrect mode Since the -wireframe mechanism evidently tracks moving
--nowirecopyrect windows accurately, a speedup can be obtained by
- telling the VNC viewers to locally copy the translated
- window region. This is the VNC CopyRect encoding:
- the framebuffer update doesn't need to send the actual
- new image data.
-
- Shorter aliases: -wcr [mode] and -nowcr
-
- "mode" can be "never" (same as -nowirecopyrect)
- to never try the copyrect, "top" means only do it if
- the window was not covered by any other windows, and
- "always" means to translate the orginally unobscured
- region (this may look odd as the remaining pieces come
- in, but helps on a slow link). Default: "always"
-
- Note: there can be painting errors or slow response
- when using -scale so you may want to disable CopyRect
- in this case "-wirecopyrect never" on the command
- line or by remote-control. Or you can also use the
- "-scale xxx:nocr" scale option.
-
--debug_wireframe Turn on debugging info printout for the wireframe
- heuristics. "-dwf" is an alias. Specify multiple
- times for more output.
-
--scrollcopyrect mode Like -wirecopyrect, but use heuristics to try to guess
--noscrollcopyrect if a window has scrolled its contents (either vertically
- or horizontally). This requires the RECORD X extension
- to "snoop" on X applications (currently for certain
- XCopyArea and XConfigureWindow X protocol requests).
- Examples: Hitting <Return> in a terminal window when the
- cursor was at the bottom, the text scrolls up one line.
- Hitting <Down> arrow in a web browser window, the web
- page scrolls up a small amount. Or scrolling with a
- scrollbar or mouse wheel.
-
- Shorter aliases: -scr [mode] and -noscr
-
- This scheme will not always detect scrolls, but when
- it does there is a nice speedup from using the VNC
- CopyRect encoding (see -wirecopyrect). The speedup
- is both in reduced network traffic and reduced X
- framebuffer polling/copying. On the other hand, it may
- induce undesired transients (e.g. a terminal cursor
- being scrolled up when it should not be) or other
- painting errors (window tearing, bunching-up, etc).
- These are automatically repaired in a short period
- of time. If this is unacceptable disable the feature
- with -noscrollcopyrect.
-
- Screen clearing kludges: for testing at least, there
- are some "magic key sequences" (must be done in less
- than 1 second) to aid repairing painting errors that
- may be seen when using this mode:
-
- 3 Alt_L's in a row: resend whole screen,
- 4 Alt_L's in a row: reread and resend whole screen,
- 3 Super_L's in a row: mark whole screen for polling,
- 4 Super_L's in a row: reset RECORD context,
- 5 Super_L's in a row: try to push a black screen
-
- note: Alt_L is the Left "Alt" key (a single key)
- Super_L is the Left "Super" key (Windows flag).
- Both of these are modifier keys, and so should not
- generate characters when pressed by themselves. Also,
- your VNC viewer may have its own refresh hot-key
- or button.
-
- "mode" can be "never" (same as -noscrollcopyrect)
- to never try the copyrect, "keys" means to try it
- in response to keystrokes only, "mouse" means to
- try it in response to mouse events only, "always"
- means to do both. Default: "always"
-
- Note: there can be painting errors or slow response
- when using -scale so you may want to disable CopyRect
- in this case "-scrollcopyrect never" on the command
- line or by remote-control. Or you can also use the
- "-scale xxx:nocr" scale option.
-
--scr_area n Set the minimum area in pixels for a rectangle
- to be considered for the -scrollcopyrect detection
- scheme. This is to avoid wasting the effort on small
- rectangles that would be quickly updated the normal way.
- E.g. suppose an app updated the position of its skinny
- scrollbar first and then shifted the large panel
- it controlled. We want to be sure to skip the small
- scrollbar and get the large panel. Default: 60000
-
--scr_skip list Skip scroll detection for applications matching
- the comma separated list of strings in "list".
- Some applications implement their scrolling in
- strange ways where the XCopyArea, etc, also applies
- to invisible portions of the window: if we CopyRect
- those areas it looks awful during the scroll and
- there may be painting errors left after the scroll.
- Soffice.bin is the worst known offender.
-
- Use "##" to denote the start of the application class
- (e.g. "##XTerm") and "++" to denote the start
- of the application instance name (e.g. "++xterm").
- The string your list is matched against is of the form
- "^^WM_NAME##Class++Instance<same-for-any-subwindows>"
- The "xlsclients -la" command will provide this info.
-
- If a pattern is prefixed with "KEY:" it only applies
- to Keystroke generated scrolls (e.g. Up arrow). If it
- is prefixed with "MOUSE:" it only applies to Mouse
- induced scrolls (e.g. dragging on a scrollbar).
- Default: ##Soffice.bin,##StarOffice,##OpenOffice
-
--scr_inc list Opposite of -scr_skip: this list is consulted first
- and if there is a match the window will be monitored
- via RECORD for scrolls irrespective of -scr_skip.
- Use -scr_skip '*' to skip anything that does not match
- your -scr_inc. Use -scr_inc '*' to include everything.
-
--scr_keys list For keystroke scroll detection, only apply the RECORD
- heuristics to the comma separated list of keysyms in
- "list". You may find the RECORD overhead for every
- one of your keystrokes disrupts typing too much, but you
- don't want to turn it off completely with "-scr mouse"
- and -scr_parms does not work or is too confusing.
-
- The listed keysyms can be numeric or the keysym
- names in the <X11/keysymdef.h> header file or from the
- xev(1) program. Example: "-scr_keys Up,Down,Return".
- One probably wants to have application specific lists
- (e.g. for terminals, etc) but that is too icky to think
- about for now...
-
- If "list" begins with the "-" character the list
- is taken as an exclude list: all keysyms except those
- list will be considered. The special string "builtin"
- expands to an internal list of keysyms that are likely
- to cause scrolls. BTW, by default modifier keys,
- Shift_L, Control_R, etc, are skipped since they almost
- never induce scrolling by themselves.
-
--scr_term list Yet another cosmetic kludge. Apply shell/terminal
- heuristics to applications matching comma separated
- list (same as for -scr_skip/-scr_inc). For example an
- annoying transient under scroll detection is if you
- hit Enter in a terminal shell with full text window,
- the solid text cursor block will be scrolled up.
- So for a short time there are two (or more) block
- cursors on the screen. There are similar scenarios,
- (e.g. an output line is duplicated).
-
- These transients are induced by the approximation of
- scroll detection (e.g. it detects the scroll, but not
- the fact that the block cursor was cleared just before
- the scroll). In nearly all cases these transient errors
- are repaired when the true X framebuffer is consulted
- by the normal polling. But they are distracting, so
- what this option provides is extra "padding" near the
- bottom of the terminal window: a few extra lines near
- the bottom will not be scrolled, but rather updated
- from the actual X framebuffer. This usually reduces
- the annoying artifacts. Use "none" to disable.
- Default: "term"
-
--scr_keyrepeat lo-hi If a key is held down (or otherwise repeats rapidly) and
- this induces a rapid sequence of scrolls (e.g. holding
- down an Arrow key) the "scrollcopyrect" detection
- and overhead may not be able to keep up. A time per
- single scroll estimate is performed and if that estimate
- predicts a sustainable scrollrate of keys per second
- between "lo" and "hi" then repeated keys will be
- DISCARDED to maintain the scrollrate. For example your
- key autorepeat may be 25 keys/sec, but for a large
- window or slow link only 8 scrolls per second can be
- sustained, then roughly 2 out of every 3 repeated keys
- will be discarded during this period. Default: "4-20"
-
--scr_parms string Set various parameters for the scrollcopyrect mode.
- The format is similar to that for -wireframe and packed
- with lots of parameters:
-
- Format: T+B+L+R,t1+t2+t3,s1+s2+s3+s4+s5
- Default: 0+64+32+32,0.02+0.10+0.9,0.03+0.06+0.5+0.1+5.0
-
- If you leave nothing between commas: ",," the default
- value is used. If you don't specify enough commas,
- the trailing parameters are set to their defaults.
-
- "T+B+L+R" indicates four integers for how close in
- pixels the pointer has to be from the Top, Bottom, Left,
- or Right edges of the window to consider scrollcopyrect.
- If -wireframe overlaps it takes precedence. This is a
- speedup to quickly exclude a window from being watched
- for scrollcopyrect: set them all to zero to not try
- the speedup (things like selecting text will likely
- be slower).
-
- "t1+t2+t3" specify three floating point times in
- seconds that apply to scrollcopyrect detection with
- *Keystroke* input: t1 is how long to wait after a key
- is pressed for the first scroll, t2 is how long to keep
- looking after a Keystroke scroll for more scrolls.
- t3 is how frequently to try to update surrounding
- scrollbars outside of the scrolling area (0.0 to
- disable)
-
- "s1+s2+s3+s4+s5" specify five floating point times
- in seconds that apply to scrollcopyrect detection with
- *Mouse* input: s1 is how long to wait after a mouse
- button is pressed for the first scroll, s2 is how long
- to keep waiting for additional scrolls after the first
- Mouse scroll was detected. s3 is how frequently to
- try to update surrounding scrollbars outside of the
- scrolling area (0.0 to disable). s4 is how long to
- buffer pointer motion (to try to get fewer, bigger
- mouse scrolls). s5 is the maximum time to spend just
- updating the scroll window without updating the rest
- of the screen.
-
--fixscreen string Periodically "repair" the screen based on settings
- in "string". Hopefully you won't need this option,
- it is intended for cases when the -scrollcopyrect or
- -wirecopyrect features leave too many painting errors,
- but it can be used for any scenario. This option
- periodically performs costly operations and so
- interactive response may be reduced when it is on.
- You can use 3 Alt_L's (the Left "Alt" key) taps in
- a row (as described under -scrollcopyrect) instead to
- manually request a screen repaint when it is needed.
-
- "string" is a comma separated list of one or more of
- the following: "V=t", "C=t", "X=t", and "8=t".
- In these "t" stands for a time in seconds (it is
- a floating point even though one should usually use
- values > 2 to avoid wasting resources). V sets how
- frequently the entire screen should be sent to viewers
- (it is like the 3 Alt_L's). C sets how long to wait
- after a CopyRect to repaint the full screen. X sets
- how frequently to reread the full X11 framebuffer from
- the X server and push it out to connected viewers.
- Use of X should be rare, please report a bug if you
- find you need it. 8= applies only for -8to24 mode: it
- sets how often the non-default visual regions of the
- screen (e.g. 8bpp windows) are refreshed. Examples:
- -fixscreen V=10 -fixscreen C=10
-
--debug_scroll Turn on debugging info printout for the scroll
- heuristics. "-ds" is an alias. Specify it multiple
- times for more output.
-
--noxrecord Disable any use of the RECORD extension. This is
- currently used by the -scrollcopyrect scheme and to
- monitor X server grabs.
-
--grab_buster Some of the use of the RECORD extension can leave a
--nograb_buster tiny window for XGrabServer deadlock. This is only if
- the whole-server grabbing application expects mouse or
- keyboard input before releasing the grab. It is usually
- a window manager that does this. x11vnc takes care to
- avoid the problem, but if caught x11vnc will freeze.
- Without -grab_buster, the only solution is to go the
- physical display and give it some input to satisfy the
- grabbing app. Or manually kill and restart the window
- manager if that is feasible. With -grab_buster, x11vnc
- will fork a helper thread and if x11vnc appears to be
- stuck in a grab after a period of time (20-30 sec) then
- it will inject some user input: button clicks, Escape,
- mouse motion, etc to try to break the grab. If you
- experience a lot of grab deadlock, please report a bug.
-
--debug_grabs Turn on debugging info printout with respect to
- XGrabServer() deadlock for -scrollcopyrect mode.
-
--debug_sel Turn on debugging info printout with respect to
- PRIMARY, CLIPBOARD, and CUTBUFFER0 selections.
-
--pointer_mode n Various pointer motion update schemes. "-pm" is
- an alias. The problem is pointer motion can cause
- rapid changes on the screen: consider the rapid
- changes when you drag a large window around opaquely.
- Neither x11vnc's screen polling and vnc compression
- routines nor the bandwidth to the vncviewers can keep
- up these rapid screen changes: everything will bog down
- when dragging or scrolling. So a scheme has to be used
- to "eat" much of that pointer input before re-polling
- the screen and sending out framebuffer updates. The
- mode number "n" can be 0 to 4 and selects one of
- the schemes desribed below.
-
- Note that the -wireframe and -scrollcopyrect modes
- complement -pointer_mode by detecting (and improving)
- certain periods of "rapid screen change".
-
- n=0: does the same as -nodragging. (all screen polling
- is suspended if a mouse button is pressed.)
-
- n=1: was the original scheme used to about Jan 2004:
- it basically just skips -input_skip keyboard or pointer
- events before repolling the screen.
-
- n=2 is an improved scheme: by watching the current rate
- of input events it tries to detect if it should try to
- "eat" additional pointer events before continuing.
-
- n=3 is basically a dynamic -nodragging mode: it detects
- when the mouse motion has paused and then refreshes
- the display.
-
- n=4 attempts to measures network rates and latency,
- the video card read rate, and how many tiles have been
- changed on the screen. From this, it aggressively tries
- to push screen "frames" when it decides it has enough
- resources to do so. NOT FINISHED.
-
- The default n is 2. Note that modes 2, 3, 4 will skip
- -input_skip keyboard events (but it will not count
- pointer events). Also note that these modes are not
- available in -threads mode which has its own pointer
- event handling mechanism.
-
- To try out the different pointer modes to see which
- one gives the best response for your usage, it is
- convenient to use the remote control function, for
- example "x11vnc -R pm:4" or the tcl/tk gui (Tuning ->
- pointer_mode -> n).
-
--input_skip n For the pointer handling when non-threaded: try to
- read n user input events before scanning display. n < 0
- means to act as though there is always user input.
- Default: 10
-
--allinput Have x11vnc read and process all available client input
- before proceeding.
-
--input_eagerly Similar to -allinput but use the handleEventsEagerly
- mechanism built into LibVNCServer.
-
--speeds rd,bw,lat x11vnc tries to estimate some speed parameters that
- are used to optimize scheduling (e.g. -pointer_mode
- 4, -wireframe, -scrollcopyrect) and other things.
- Use the -speeds option to set these manually.
- The triple "rd,bw,lat" corresponds to video h/w
- read rate in MB/sec, network bandwidth to clients in
- KB/sec, and network latency to clients in milliseconds,
- respectively. If a value is left blank, e.g. "-speeds
- ,100,15", then the internal scheme is used to estimate
- the empty value(s).
-
- Typical PC video cards have read rates of 5-10 MB/sec.
- If the framebuffer is in main memory instead of video
- h/w (e.g. SunRay, shadowfb, dummy driver, Xvfb), the
- read rate may be much faster. "x11perf -getimage500"
- can be used to get a lower bound (remember to factor
- in the bytes per pixel). It is up to you to estimate
- the network bandwith and latency to clients. For the
- latency the ping(1) command can be used.
-
- For convenience there are some aliases provided,
- e.g. "-speeds modem". The aliases are: "modem" for
- 6,4,200; "dsl" for 6,100,50; and "lan" for 6,5000,1
-
--wmdt string For some features, e.g. -wireframe and -scrollcopyrect,
- x11vnc has to work around issues for certain window
- managers or desktops (currently kde and xfce).
- By default it tries to guess which one, but it can
- guess incorrectly. Use this option to indicate which
- wm/dt. "string" can be "gnome", "kde", "cde",
- "xfce", or "root" (classic X wm). Anything else
- is interpreted as "root".
-
--debug_pointer Print debugging output for every pointer event.
--debug_keyboard Print debugging output for every keyboard event.
- Same as -dp and -dk, respectively. Use multiple
- times for more output.
-
--defer time Time in ms to delay sending updates to connected clients
- (deferUpdateTime) Default: 20
-
--wait time Time in ms to pause between screen polls. Used to cut
- down on load. Default: 20
-
--extra_fbur n Perform extra FrameBufferUpdateRequests checks to
- try to be in better sync with the client's requests.
- What this does is perform extra polls of the client
- socket at critical times (before '-defer' and '-wait'
- calls.) The default is n=1. Set to a larger number to
- insert more checks or set to n=0 to disable. A downside
- of these extra calls is that more mouse input may be
- processed than desired.
-
--wait_ui factor Factor by which to cut the -wait time if there
- has been recent user input (pointer or keyboard).
- Improves response, but increases the load whenever you
- are moving the mouse or typing. Default: 2.00
--setdefer n When the -wait_ui mechanism cuts down the wait time ms,
- set the defer time to the same ms value. n=1 to enable,
- 0 to disable, and -1 to set defer to 0 (no delay).
- Similarly, 2 and -2 indicate 'urgent_update' mode should
- be used to push the updates even sooner. Default: 1
--nowait_bog Do not detect if the screen polling is "bogging down"
- and sleep more. Some activities with no user input can
- slow things down a lot: consider a large terminal window
- with a long build running in it continuously streaming
- text output. By default x11vnc will try to detect this
- (3 screen polls in a row each longer than 0.25 sec with
- no user input), and sleep up to 1.5 secs to let things
- "catch up". Use this option to disable that detection.
--slow_fb time Floating point time in seconds to delay all screen
- polling. For special purpose usage where a low frame
- rate is acceptable and desirable, but you want the
- user input processed at the normal rate so you cannot
- use -wait.
--xrefresh time Floating point time in seconds to indicate how often to
- do the equivalent of xrefresh(1) to force all windows
- (in the viewable area if -id, -sid, or -clip is used)
- to repaint themselves. Use this only if applications
- misbehave by not repainting themselves properly.
- See also -noxdamage.
--nap Monitor activity and if it is low take longer naps
--nonap between screen polls to really cut down load when idle.
- Default: take naps
--sb time Time in seconds after NO activity (e.g. screen blank)
- to really throttle down the screen polls (i.e. sleep
- for about 1.5 secs). Use 0 to disable. Default: 60
- Set the env. var. X11VNC_SB_FACTOR to scale it.
-
--readtimeout n Set LibVNCServer rfbMaxClientWait to n seconds. On
- slow links that take a long time to paint the first
- screen LibVNCServer may hit the timeout and drop the
- connection. Default: 20 seconds.
--ping n Send a 1x1 framebuffer update to all clients every n
- seconds (e.g. to try to keep a network connection alive)
-
--nofbpm If the system supports the FBPM (Frame Buffer Power
--fbpm Management) extension (i.e. some Sun systems), then
- prevent the video h/w from going into a reduced power
- state when VNC clients are connected.
-
- FBPM capable video h/w save energy when the workstation
- is idle by going into low power states (similar to DPMS
- for monitors). This interferes with x11vnc's polling
- of the framebuffer data.
-
- "-nofbpm" means prevent FBPM low power states whenever
- VNC clients are connected, while "-fbpm" means to not
- monitor the FBPM state at all. See the xset(1) manpage
- for details. -nofbpm is basically the same as running
- "xset fbpm force on" periodically. Default: -fbpm
-
--nodpms If the system supports the DPMS (Display Power Managemen
-t
--dpms Signaling) extension, then prevent the monitor from
- going into a reduced power state when VNC clients
- are connected.
-
- DPMS reduced power monitor states are a good thing
- and you normally want the power down to take place
- (usually x11vnc has no problem exporting the display in
- this state). You probably only want to use "-nodpms"
- to work around problems with Screen Savers kicking
- on in DPMS low power states. There is known problem
- with kdesktop_lock on KDE where the screen saver keeps
- kicking in every time user input stops for a second
- or two. Specifying "-nodpms" works around it.
-
- "-nodpms" means prevent DPMS low power states whenever
- VNC clients are connected, while "-dpms" means to not
- monitor the DPMS state at all. See the xset(1) manpage
- for details. -nodpms is basically the same as running
- "xset dpms force on" periodically. Default: -dpms
-
--forcedpms If the system supports the DPMS (Display Power
- Management Signaling) extension, then try to keep the
- monitor in a powered off state. This is to prevent
- nosey people at the physical display from viewing what
- is on the screen. Be sure to lock the screen before
- disconnecting.
-
- This method is far from bullet proof, e.g. suppose
- someone attaches a non-DPMS monitor, or loads the
- machine so that there is a gap of time before x11vnc
- restores the powered off state? On many machines if
- he floods it with keyboard and mouse input he can see
- flashes of what is on the screen before the DPMS off
- state is reestablished. For this to work securely
- there would need to be support in the X server to do
- this exactly rather than approximately with DPMS.
-
--clientdpms As -forcedpms but only when VNC clients are connected.
-
--noserverdpms The UltraVNC ServerInput extension is supported.
- This allows the VNC viewer to click a button that will
- cause the server (x11vnc) to try to disable keyboard
- and mouse input at the physical display and put the
- monitor in dpms powered off state. Use this option to
- skip powering off the monitor.
-
--noultraext Disable the following UltraVNC extensions: SingleWindow
- and ServerInput. The others managed by LibVNCServer
- (textchat, 1/n scaling, rfbEncodingUltra) are not.
-
--chatwindow Place a local UltraVNC chat window on the X11 display
- that x11vnc is polling. That way the person on the VNC
- viewer-side can chat with the person at the physical
- X11 console. (e.g. helpdesk w/o telephone)
-
- For this to work the SSVNC package (version 1.0.21 or
- later) MUST BE installed on the system where x11vnc runs
- and the 'ssvnc' command must be available in $PATH.
- The ssvncviewer is used as a chat window helper.
- See http://www.karlrunge.com/x11vnc/ssvnc.html
-
- This option implies '-rfbversion 3.6' so as to trick
- UltraVNC viewers, otherwise they assume chat is not
- available. To specify a different rfbversion, place
- it after the -chatwindow option on the cmdline.
-
- See also the remote control 'chaton' and 'chatoff'
- actions. These can also be set from the tkx11vnc GUI.
-
--noxdamage Do not use the X DAMAGE extension to detect framebuffer
- changes even if it is available. Use -xdamage if your
- default is to have it off.
-
- x11vnc's use of the DAMAGE extension: 1) significantly
- reduces the load when the screen is not changing much,
- and 2) detects changed areas (small ones by default)
- more quickly.
-
- Currently the DAMAGE extension is overly conservative
- and often reports large areas (e.g. a whole terminal
- or browser window) as damaged even though the actual
- changed region is much smaller (sometimes just a few
- pixels). So heuristics were introduced to skip large
- areas and use the damage rectangles only as "hints"
- for the traditional scanline polling. The following
- tuning parameters are introduced to adjust this
- behavior:
-
--xd_area A Set the largest DAMAGE rectangle area "A" (in
- pixels: width * height) to trust as truly damaged:
- the rectangle will be copied from the framebuffer
- (slow) no matter what. Set to zero to trust *all*
- rectangles. Default: 20000
--xd_mem f Set how long DAMAGE rectangles should be "remembered",
- "f" is a floating point number and is in units of the
- scanline repeat cycle time (32 iterations). The default
- (1.0) should give no painting problems. Increase it if
- there are problems or decrease it to live on the edge
- (perhaps useful on a slow machine).
-
--sigpipe string Broken pipe (SIGPIPE) handling. "string" can be
- "ignore" or "exit". For "ignore" LibVNCServer
- will handle the abrupt loss of a client and continue,
- for "exit" x11vnc will cleanup and exit at the 1st
- broken connection.
-
- This option is not really needed since LibVNCServer
- is doing the correct thing now for quite some time.
- However, for convenience you can use it to ignore other
- signals, e.g. "-sigpipe ignore:HUP,INT,TERM" in case
- that would be useful for some sort of application.
- You can also put "exit:.." in the list to have x11vnc
- cleanup on the listed signals. "-sig" is an alias
- for this option if you don't like the 'pipe'. Example:
- -sig ignore:INT,TERM,exit:USR1
-
--threads Whether or not to use the threaded LibVNCServer
--nothreads algorithm [rfbRunEventLoop] if libpthread is available.
- In this mode new threads (one for input and one
- for output) are created to handle each new client.
- Default: -nothreads.
-
- Thread stability is much improved in version 0.9.8.
-
- Multiple clients in threaded mode should be stable
- for the ZRLE encoding on all platforms. The Tight and
- Zlib encodings are currently only stable on Linux for
- multiple clients. Compile with -DTLS=__thread if your
- OS and compiler and linker support it.
-
- For resizes (randr, etc.) set this env. var. to the numb
-er
- of milliseconds to sleep: X11VNC_THREADS_NEW_FB_SLEEP
- at various places in the do_new_fb() action. This is to
- let various activities settle. Default is about 500ms.
-
- Multiple clients in threaded mode could yield better
- performance for 'class-room' broadcasting usage; also in
- -appshare broadcast mode. See also the -reflect option.
-
--fs f If the fraction of changed tiles in a poll is greater
- than f, the whole screen is updated. Default: 0.75
--gaps n Heuristic to fill in gaps in rows or cols of n or
- less tiles. Used to improve text paging. Default: 4
--grow n Heuristic to grow islands of changed tiles n or wider
- by checking the tile near the boundary. Default: 3
--fuzz n Tolerance in pixels to mark a tiles edges as changed.
- Default: 2
--debug_tiles Print debugging output for tiles, fb updates, etc.
-
--snapfb Instead of polling the X display framebuffer (fb)
- for changes, periodically copy all of X display fb
- into main memory and examine that copy for changes.
- (This setting also applies for non-X -rawfb modes).
- Under some circumstances this will improve interactive
- response, or at least make things look smoother, but in
- others (most!) it will make the response worse. If the
- video h/w fb is such that reading small tiles is very
- slow this mode could help. To keep the "framerate"
- up the screen size x bpp cannot be too large. Note that
- this mode is very wasteful of memory I/O resources
- (it makes full screen copies even if nothing changes).
- It may be of use in video capture-like applications,
- webcams, or where window tearing is a problem.
-
--rawfb string Instead of polling X, poll the memory object specified
- in "string".
-
- For file polling, to memory map mmap(2) a file use:
- "map:/path/to/a/file@WxHxB", with framebuffer Width,
- Height, and Bits per pixel. "mmap:..." is the
- same.
-
- If there is trouble with mmap, use "file:/..."
- for slower lseek(2) based reading.
-
- Use "snap:..." to imply -snapfb mode and the "file:"
- access (this is for unseekable devices that only provide
- the fb all at once, e.g. a video camera provides the
- whole frame).
-
- For shared memory segments string is of the form:
- "shm:N@WxHxB" which specifies a shmid N and with
- WxHxB as above. See shmat(1) and ipcs(1)
-
- If you do not supply a type "map" is assumed if
- the file exists (see the next paragraphs for some
- exceptions to this.)
-
- If string is "setup:cmd", then the command "cmd"
- is run and the first line from it is read and used
- as "string". This allows initializing the device,
- determining WxHxB, etc. These are often done as root
- so take care.
-
- If the string begins with "video", see the VIDEO4LINUX
- discussion below where the device may be queried for
- (and possibly set) the framebuffer parameters.
-
- If the string begins with "console", "/dev/fb",
- "fb", or "vt", see the LINUX CONSOLE discussion
- below where the framebuffer device is opened and
- keystrokes (and possibly mouse events) are inserted
- into the console.
-
- If the string begins with "vnc", see the VNC HOST
- discussion below where the framebuffer is taken as that
- of another remote VNC server.
-
- Optional suffixes are ":R/G/B" and "+O" to specify
- red, green, and blue masks (in hex) and an offset into
- the memory object. If the masks are not provided x11vnc
- guesses them based on the bpp (if the colors look wrong,
- you need to provide the masks.)
-
- Another optional suffix is the Bytes Per Line which in
- some cases is not WxB/8. Specify it as WxHxB-BPL
- e.g. 800x600x16-2048. This could be a normal width
- 1024 at 16bpp fb, but only width 800 shows up.
-
- So the full format is: mode:file@WxHxB:R/G/B+O-BPL
-
- Examples:
- -rawfb shm:210337933@800x600x32:ff/ff00/ff0000
- -rawfb map:/dev/fb0@1024x768x32
- -rawfb map:/tmp/Xvfb_screen0@640x480x8+3232
- -rawfb file:/tmp/my.pnm@250x200x24+37
- -rawfb file:/dev/urandom@128x128x8
- -rawfb snap:/dev/video0@320x240x24 -24to32
- -rawfb video0
- -rawfb video -pipeinput VID
- -rawfb console
- -rawfb vt2
- -rawfb vnc:somehost:0
-
- (see ipcs(1) and fbset(1) for the first two examples)
-
- In general all user input is discarded by default (see
- the -pipeinput option for how to use a helper program
- to insert). Most of the X11 (screen, keyboard, mouse)
- options do not make sense and many will cause this
- mode to crash, so please think twice before setting or
- changing them in a running x11vnc.
-
- If you DO NOT want x11vnc to close the X DISPLAY in
- rawfb mode, prepend a "+" e.g. +file:/dev/fb0...
- Keeping the display open enables the default
- remote-control channel, which could be useful.
- Alternatively, if you specify -noviewonly, then the
- mouse and keyboard input are STILL sent to the X
- display, this usage should be very rare, i.e. doing
- something strange with /dev/fb0.
-
- If the device is not "seekable" (e.g. webcam) try
- reading it all at once in full snaps via the "snap:"
- mode (note: this is a resource hog). If you are using
- file: or map: AND the device needs to be reopened for
- *every* snapfb snapshot, set the environment variable:
- SNAPFB_RAWFB_RESET=1 as well.
-
- If you want x11vnc to dynamically transform a 24bpp
- rawfb to 32bpp (note that this will be slower) also
- supply the -24to32 option. This would be useful for,
- say, a video camera that delivers the pixel data as
- 24bpp packed RGB. This is the default under "video"
- mode if the bpp is 24.
-
- Normally the bits per pixel, B, is 8, 16, or 32 (or
- rarely 24), however there is also some support for
- B < 8 (e.g. old graphics displays 4 bpp or 1 bpp).
- In this case you certainly must supply the masks as
- well: WxHxB:R/G/B. The pixels will be padded out to
- 8 bpp using depth 8 truecolor. The scheme currently
- does not work with snap fb (ask if interested.) B=1
- monochrome example: file:/dev/urandom@128x128x1:1/1/1
- Some other like this are 128x128x2:3/3/3 128x128x4:7/7/7
-
- For B < 8 framebuffers you can also set the env. var
- RAWFB_CGA=1 to try a CGA mapping for B=4 (e.g. linux
- vga16fb driver.) Note with low bpp and/or resolution
- VGA and VGA16 modes on the Linux console one's attempt
- to export them via x11vnc can often be thwarted due to
- special color palettes, pixel packings, and even video
- painting buffering. OTOH, often experimenting with the
- RGB masks can yield something recognizable.
-
- VIDEO4LINUX: on Linux some attempt is made to handle
- video devices (webcams or TV tuners) automatically.
- The idea is the WxHxB will be extracted from the
- device itself. So if you do not supply "@WxHxB...
- parameters x11vnc will try to determine them. It first
- tries the v4l API if that support has been compiled in.
- Otherwise it will run the v4l-info(1) external program
- if it is available.
-
- The simplest examples are "-rawfb video" and "-rawfb
- video1" which imply the device file /dev/video and
- /dev/video1, respectively. You can also supply the
- /dev if you like, e.g. "-rawfb /dev/video0"
-
- Since the video capture device framebuffer usually
- changes continuously (e.g. brightness fluctuations),
- you may want to use the -wait, -slow_fb, or -defer
- options to lower the "framerate" to cut down on
- network VNC traffic.
-
- A more sophisticated video device scheme allows
- initializing the device's settings using:
-
- -rawfb video:<settings>
-
- The prefix could also be, as above, e.g. "video1:" to
- specify the device file. The v4l API must be available
- for this to work. Otherwise, you will need to try
- to initialize the device with an external program,
- e.g. xawtv, spcaview, and hope they persist when x11vnc
- re-opens the device.
-
- <settings> is a comma separated list of key=value pairs.
- The device's brightness, color, contrast, and hue can
- be set to percentages, e.g. br=80,co=50,cn=44,hu=60.
-
- The device filename can be set too if needed (if it
- does not start with "video"), e.g. fn=/dev/qcam.
-
- The width, height and bpp of the framebuffer can be
- set via, e.g., w=160,h=120,bpp=16.
-
- Related to the bpp above, the pixel format can be set
- via the fmt=XXX, where XXX can be one of: GREY, HI240,
- RGB555, RGB565, RGB24, and RGB32 (with bpp 8, 8, 16, 16,
- 24, and 32 respectively). See http://www.linuxtv.org
- for more info (V4L api).
-
- For TV/rf tuner cards one can set the tuning mode
- via tun=XXX where XXX can be one of PAL, NTSC, SECAM,
- or AUTO.
-
- One can switch the input channel by the inp=XXX setting,
- where XXX is the name of the input channel (Television,
- Composite1, S-Video, etc). Use the name that is in the
- information about the device that is printed at startup.
-
- For input channels with tuners (e.g. Television) one
- can change which station is selected by the sta=XXX
- setting. XXX is the station number. Currently only
- the ntsc-cable-us (US cable) channels are built into
- x11vnc. See the -freqtab option below to supply one
- from xawtv. If XXX is greater than 500, then it is
- interpreted as a raw frequency in KHz.
-
- Example:
-
- -rawfb video:br=80,w=320,h=240,fmt=RGB32,tun=NTSC,sta=47
-
- one might need to add inp=Television too for the input
- channel to be TV if the card doesn't come up by default
- in that one.
-
- Note that not all video capture devices will support
- all of the above settings.
-
- See the -pipeinput VID option below for a way to control
- the settings through the VNC Viewer via keystrokes.
- As a shortcut, if the string begins "Video.." instead
- of "video.." then -pipeinput VID is implied.
-
- As above, if you specify a "@WxHxB..." after the
- <settings> string they are used verbatim: the device
- is not queried for the current values. Otherwise the
- device will be queried.
-
- LINUX CONSOLE: The following describes some ways to
- view and possibly interact with the Linux text/graphics
- console (i.e. not X11 XFree86/Xorg)
-
- Note: If the LibVNCServer LinuxVNC program is on your
- system you may want to use that instead of the following
- method because it will be faster and more accurate
- for the Linux text console and includes mouse support.
- There is, however, the basic LinuxVNC functionality in
- x11vnc if you replace "console" with "vt" in the
- examples below.
-
- If the rawfb string begins with "console" the
- framebuffer device /dev/fb0 is opened and /dev/tty0 is
- opened too. The latter is used to inject keystrokes
- (not all are supported, but the basic ones are).
- You will need to be root to inject keystrokes, but
- not necessarily to open /dev/fb0. /dev/tty0 refers to
- the active VT, to indicate one explicitly, use, e.g.,
- "console2" for /dev/tty2, etc. by indicating the
- specific VT number.
-
- For the Linux framebuffer device, /dev/fb0, (fb1,
- etc) to be enabled the appropriate kernel drivers must
- be loaded. E.g. vesafb or vga16fb and also by setting
- the boot parameter vga=0x301 (or 0x314, 0x317, etc.)
- (The vga=... method is the preferred way; set your
- machines up that way.) Otherwise there will be a
- 'No such device' error. You can also load a Linux
- framebuffer driver specific to your make of video card
- for more functionality. Once the machine is booted one
- can often 'modprobe' the fb driver as root to obtain
- a framebuffer device.
-
- If you cannot get /dev/fb0 working on Linux, try
- using the LinuxVNC emulation mode by "-rawfb vtN"
- where N = 1, ... 6 is the Linux Virtual Terminal (aka
- virtual console) you wish to view, e.g. "-rawfb vt2".
- Unlike /dev/fb mode, it need not be the active Virtual
- Terminal. Note that this mode can only show text and
- not graphics. x11vnc polls the text in /dev/vcsaN
-
- Set the env. var. RAWFB_VCSA_BW=1 to disable colors in
- the "vtN" mode (i.e. black and white only.) If you
- do not prefer the default 16bpp set RAWFB_VCSA_BPP to
- 8 or 32. If you need to tweak the rawfb parameters by
- using the 'console_guess' string printed at startup,
- be sure to indicate the snap: method.
-
- uinput: If the Linux version appears to be 2.6
- or later and the "uinput" module appears to be
- present (modprobe uinput), then the uinput method
- will be used instead of /dev/ttyN. uinput allows
- insertion of BOTH keystrokes and mouse input and so it
- preferred when accessing graphical (e.g. QT-embedded)
- linux console apps. It also provides more accurate
- keystroke insertion. See -pipeinput UINPUT below for
- more information on this mode; you will have to use
- -pipeinput if you want to tweak any UINPUT parameters.
- You may also want to also use the -nodragging and
- -cursor none options. Use "console0", etc or
- -pipeinput CONSOLE to force the /dev/ttyN method.
-
- Note you can change the Linux VT remotely using the
- chvt(1) command to make the one you want be the active
- one (e.g. 'chvt 3'). Sometimes switching out and back
- corrects the framebuffer's graphics state. For the
- "-rawfb vtN" mode there is no need to switch the VT's.
-
- To skip input injecting entirely use "consolex"
- or "vtx".
-
- The string "/dev/fb0" (1, etc.) can be used instead
- of "console". This can be used to specify a different
- framebuffer device, e.g. /dev/fb1. As a shortcut the
- "/dev/" can be dropped. If the name is something
- nonstandard, use "console:/dev/foofb"
-
- If you do not want x11vnc to guess the framebuffer's
- WxHxB and masks automatically (sometimes the kernel
- gives incorrect information), specify them with a @WxHxB
- (and optional :R/G/B masks) at the end of the string.
-
- Examples:
- -rawfb console
- -rawfb /dev/fb0 (same)
- -rawfb console3 (force /dev/tty3)
- -rawfb consolex (no keystrokes or mouse)
- -rawfb console:/dev/nonstd
- -rawfb console -pipeinput UINPUT:accel=4.0
- -rawfb vt3 (/dev/tty3 w/o /dev/fb0)
-
- VNC HOST: if the -rawfb string is of the form
- "vnc:host:N" then the VNC display "N" on the remote
- VNC server "host" is connected to (i.e. x11vnc acts as
- a VNC client itself) and that framebuffer is exported.
-
- This mode is really only of use if you are trying
- to improve performance in the case of many (e.g. >
- 10) simultaneous VNC viewers, and you try a divide
- and conquer scheme to reduce bandwidth and improve
- responsiveness. (However, another user found this mode
- useful to export a demo display through a slow link:
- then multiple demo viewers connected to the reflecting
- x11vnc on the fast side of the link, and so avoided
- all of the demo viewers going through the slow link.)
-
- For example, if there will be 64 simultaneous VNC
- viewers this can lead to a lot of redundant VNC traffic
- to and from the server host:N, extra CPU usage,
- and all viewers response can be reduced by having
- to wait for writes to the slowest client to finish.
- However, if you set up 8 reflectors/repeaters started
- with option -rawfb vnc:host:N, then there are only
- 8 connections to host:N. Each repeater then handles
- 8 vnc viewer connections thereby spreading the load
- around. In classroom broadcast usage, try to put the
- repeaters on different switches. This mode is the same
- as -reflect host:N. Replace "host:N" by "listen"
- or "listen:port" for a reverse connection.
-
- Overall performance will not be as good as a single
- direct connection because, among other things,
- there is an additional level of framebuffer polling
- and pointer motion can still induce many changes per
- second that must be propagated. Tip: if the remote VNC
- is x11vnc doing wireframing, or an X display that does
- wireframing that gives much better response than opaque
- window dragging. Consider the -nodragging option if
- the problem is severe.
-
- The env. var. X11VNC_REFLECT_PASSWORD can be set to
- the password needed to log into the vnc host server, or
- to "file:path_to_file" to indicate a file containing
- the password as its first line.
-
- To set the pixel format that x11vnc requests as a VNC
- CLIENT set the env. vars: X11VNC_REFLECT_bitsPerSample
- X11VNC_REFLECT_samplesPerPixel, and
- X11VNC_REFLECT_bytesPerPixel; the defaults are 8, 3, 4.
- 2, 3, 1 would give a low color mode. See the function
- rfbGetClient() in libvncclient for more info.
-
- The VNC HOST mode implies -shared. Use -noshared as
- a subsequent cmdline option to disable sharing.
-
--freqtab file For use with "-rawfb video" for TV tuner devices to
- specify station frequencies. Instead of using the built
- in ntsc-cable-us mapping of station number to frequency,
- use the data in file. For stations that are not
- numeric, e.g. SE20, they are placed above the highest
- numbered station in the order they are found. Example:
- "-freqtab /usr/X11R6/share/xawtv/europe-west.list"
- You can make your own freqtab by copying the xawtv
- format.
-
--pipeinput cmd This option lets you supply an external command in
- "cmd" that x11vnc will pipe all of the user input
- events to in a simple format. In -pipeinput mode by
- default x11vnc will not process any of the user input
- events. If you prefix "cmd" with "tee:" it will
- both send them to the pipe command and process them.
- For a description of the format run "-pipeinput
- tee:/bin/cat". Another prefix is "reopen" which
- means to reopen pipe if it exits. Separate multiple
- prefixes with commas.
-
- In combination with -rawfb one might be able to
- do amusing things (e.g. control non-X devices).
- To facilitate this, if -rawfb is in effect then the
- value is stored in X11VNC_RAWFB_STR for the pipe command
- to use if it wants. Do 'env | grep X11VNC' for more.
-
- Built-in pipeinput modes (no external program required):
-
- If cmd is "VID" and you are using the -rawfb for a
- video capture device, then an internal list of keyboard
- mappings is used to set parameters of the video.
- The mappings are:
-
- "B" and "b" adjust the brightness up and down.
- "H" and "h" adjust the hue.
- "C" and "c" adjust the colour.
- "N" and "n" adjust the contrast.
- "S" and "s" adjust the size of the capture screen.
- "I" and "i" cycle through input channels.
- Up and Down arrows adjust the station (if a tuner)
- F1, F2, ..., F6 will switch the video capture pixel
- format to HI240, RGB565, RGB24, RGB32, RGB555, and
- GREY respectively. See -rawfb video for details.
-
- If cmd is "CONSOLE" or "CONSOLEn" where n
- is a Linux console number, then the linux console
- keystroke insertion to /dev/ttyN (see -rawfb console)
- is performed.
-
- If cmd begins with "UINPUT" then the Linux uinput
- module is used to insert both keystroke and mouse events
- to the Linux console (see -rawfb above). This usually
- is the /dev/input/uinput device file (you may need to
- create it with "mknod /dev/input/uinput c 10 223"
- and insert the module with "modprobe uinput".
-
- The UINPUT mode currently only does US keyboards (a
- scan code option may be added), and not all keysyms
- are supported. But it is probably more accurate than
- the "CONSOLE" method.
-
- You may want to use the options -cursor none and
- -nodragging in this mode.
-
- Additional tuning options may be supplied via:
- UINPUT:opt1,opt2,... (a comma separated list). If an
- option begins with "/" it is taken as the uinput
- device file.
-
- Which uinput is injected can be controlled by an option
- string made of the characters "K", "M", and "B"
- (see the -input option), e.g. "KM" allows keystroke
- and motion but not button clicks.
-
- A UINPUT option of the form: accel=f, or accel=fx+fy
- sets the mouse motion "acceleration". This is used
- to correct raw mouse relative motion into how much the
- application cursor moves (x11vnc has no control over,
- or knowledge of how the windowing application interprets
- the raw mouse motions). Typically the acceleration
- for an X display is 2 (see xset "m" option). "f"
- is a floating point number, e.g. 3.0. Use "fx+fy"
- if you need to supply different corrections for x and y.
-
- Note: the default acceleration is 2.0 since it seems
- both X and qt-embedded often (but not always) use
- this value.
-
- Even with a correct accel setting the mouse position
- will get out of sync (probably due to a mouse
- "threshold" setting where the acceleration doe not
- apply, set xset(1)). The option reset=N sets the
- number of ms (default 150) after which the cursor is
- attempted to be reset (by forcing the mouse to (0,
- 0) via small increments and then back out to (x, y)
- in 1 jump), This correction seems to be needed but can
- cause jerkiness or unexpected behavior with menus, etc.
- Use reset=0 to disable.
-
- If you set the env. var X11VNC_UINPUT_THRESHOLDS then
- the thresh=n mode will be enabled. It is currently
- not working well. If |dx| <= thresh and |dy| < thresh
- no acceleration is applied. Use "thresh=+n" |dx| +
- |dy| < thresh to be used instead (X11?)
-
- Example:
- -pipeinput UINPUT:accel=4.0 -cursor none
-
- If the uinput device has an absolute pointer (as opposed
- to a normal mouse that is a relative pointer) you can
- specify the option "abs". Note that a touchpad
- on a laptop is an absolute device to some degree.
- This (usually) avoids all the problems with mouse
- acceleration. If x11vnc has trouble deducing the
- size of the device, use "abs=WxH". Furthermore,
- if the device is a touchscreen (assumed to have an
- absolute pointer) use "touch" or "touch=WxH".
- For touchscreens, when a mouse button is pressed,
- a pressure increase is injected, and when the button
- is released a pressure of zero is injected.
-
- If touch has been set, use "touch_always=1" to
- indicate whenever the mouse moves with no button
- pressed, a touch event of zero pressure should be
- sent anyway. Also use "btn_touch=1" to indicate a
- BTN_TOUCH keystroke press or release should be sent
- instead of a pressure change. Set "dragskip=n" to
- skip n dragged mouse touches (with pressure applied)
- before injecting one. To indicate the pressure that
- should be sent when there is a button click for a
- touchscreen device, specify pressure=n, e.g. n=5. The
- default is n=1.
-
- If a touch screen is being used ("touch" above)
- and it is having its input processed by tslib, you can
- specify the tslib calibration file via tslib_cal=<file>.
- For example, tslib_cal=/etc/pointercal. To get accurate
- or even usable positioning this is required when tslib
- is in use.
-
- The Linux uinput mechanism can be bypassed and one can
- write input events DIRECTLY to the devices instead.
- To do this, specify one or more of the following
- for the input classes: direct_rel=<device>
- direct_abs=<device> direct_btn=<device> or
- direct_key=<device>. The <device> file is usually
- something like /dev/input/event1 but you can specify
- any device file or pipe. You must specify each one
- of the above classes even if they correspond to the
- same device file (rel/abs and btn are often the same.)
- Look at the file /proc/bus/input/devices to get an idea
- what is available and the device filenames. Note:
- The /dev/input/mouse* devices do not seem to work,
- use the corresponding /dev/input/event* file instead.
- Any input class not directly specified as above will be
- handled via the uinput mechanism. To disable creating a
- uinput device (and thereby discarding unhandled input),
- specify "nouinput".
-
- Examples:
-
- -pipeinput UINPUT:direct_abs=/dev/input/event1
-
- this was used on a qtmoko Neo freerunner (armel):
-
- -pipeinput UINPUT:touch,tslib_cal=/etc/pointercal,
- direct_abs=/dev/input/event1,nouinput,dragskip=4
-
- (where the long line has been split into two.)
-
- You can set the env. var X11VNC_UINPUT_DEBUG=1 or higher
- to get debugging output for UINPUT mode.
-
--macnodim For the native MacOSX server, disable dimming.
--macnosleep For the native MacOSX server, disable display sleep.
--macnosaver For the native MacOSX server, disable screensaver.
--macnowait For the native MacOSX server, do not wait for the
- user to switch back to his display.
--macwheel n For the native MacOSX server, set the mouse wheel
- speed to n (default 5).
--macnoswap For the native MacOSX server, do not swap mouse
- buttons 2 and 3.
--macnoresize For the native MacOSX server, do not resize or reset
- the framebuffer even if it is detected that the screen
- resolution or depth has changed.
--maciconanim n For the native MacOSX server, set n to the number
- of milliseconds that the window iconify/deiconify
- animation takes. In -ncache mode this value will be
- used to skip the animation if possible. (default 400)
--macmenu For the native MacOSX server, in -ncache client-side
- caching mode, try to cache pull down menus (not perfect
- because they have animated fades, etc.)
--macuskbd For the native MacOSX server, use the original
- keystroke insertion code based on a US keyboard.
--macnoopengl For the native MacOSX server, do not use OpenGL for
- screen capture, but rather use the original, deprecated
- raw memory access method: addr = CGDisplayBaseAddress().
--macnorawfb For the native MacOSX server, disable the raw memory
- address screen capture method.
-
- MACOSX NOTE: There are some deprecated MacOSX interfaces
- to inject keyboard and mouse events and the raw memory
- access method is deprecated as well (however, OpenGL
- will be preferred if available because it is faster.)
- One can force not using any deprecated interfaces at
- compile time by setting -DX11VNC_MACOSX_NO_DEPRECATED=1
- in CPPFLAGS. Or to turn them off one by one:
- -DX11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1,
- -DX11VNC_MACOSX_NO_DEPRECATED_POSTEVENTS=1 or
- -DX11VNC_MACOSX_NO_DEPRECATED_FRAMEBUFFER=1
- At run time, for testing and workarounds, one can
- disable them by using:
- -env X11VNC_MACOSX_NO_DEPRECATED=1
- -env X11VNC_MACOSX_NO_DEPRECATED_LOCALEVENTS=1
- -env X11VNC_MACOSX_NO_DEPRECATED_POSTEVENTS=1 or
- -env X11VNC_MACOSX_NO_DEPRECATED_FRAMEBUFFER=1
- Note: When doing either of these for the mouse input
- not everything works currently, e.g. double clicks and
- wireframing. Also, screen resolution and pixel depth
- changes will not be automatically detected unless the
- deprecated framebuffer interfaces are allowed.
-
- Conversely, if you are compiling on an
- older machine that does not have some of
- the newer interfaces, you may need to specify
- -DX11VNC_MACOSX_NO_CGEVENTCREATESCROLLWHEELEVENT
- -DX11VNC_MACOSX_NO_CGEVENTCREATEMOUSEEVENT or
- -DX11VNC_MACOSX_NO_CGEVENTCREATEKEYBOARDEVENT. Use
- -DX11VNC_MACOSX_USE_GETMAINDEVICE to regain the very
- old QuickDraw GetMainDevice() interface (rare...)
-
--gui [gui-opts] Start up a simple tcl/tk gui based on the remote
- control options -remote/-query described below.
- Requires the "wish" program to be installed on the
- machine. "gui-opts" is not required: the default
- is to start up both the full gui and x11vnc with the
- gui showing up on the X display in the environment
- variable DISPLAY.
-
- "gui-opts" can be a comma separated list of items.
- Currently there are these types of items: 1) a gui
- mode, a 2) gui "simplicity", 3) the X display the
- gui should display on, 4) a "tray" or "icon" mode,
- and 5) a gui geometry.
-
- 1) The gui mode can be "start", "conn", or "wait"
- "start" is the default mode above and is not required.
- "conn" means do not automatically start up x11vnc,
- but instead just try to connect to an existing x11vnc
- process. "wait" means just start the gui and nothing
- else (you will later instruct the gui to start x11vnc
- or connect to an existing one.)
-
- 2) The gui simplicity is off by default (a power-user
- gui with all options is presented) To start with
- something less daunting supply the string "simple"
- ("ez" is an alias for this). Once the gui is
- started you can toggle between the two with "Misc ->
- simple_gui".
-
- 3) Note the possible confusion regarding the potentially
- two different X displays: x11vnc polls one, but you
- may want the gui to appear on another. For example, if
- you ssh in and x11vnc is not running yet you may want
- the gui to come back to you via your ssh redirected X
- display (e.g. localhost:10).
-
- If you do not specify a gui X display in "gui-opts"
- then the DISPLAY environment variable and -display
- option are tried (in that order). Regarding the x11vnc
- X display the gui will try to communication with, it
- first tries -display and then DISPLAY. For example,
- "x11vnc -display :0 -gui otherhost:0", will remote
- control an x11vnc polling :0 and display the gui on
- otherhost:0 The "tray/icon" mode below reverses this
- preference, preferring to display on the x11vnc display.
-
- 4) When "tray" or "icon" is specified, the gui
- presents itself as a small icon with behavior typical
- of a "system tray" or "dock applet". The color
- of the icon indicates status (connected clients) and
- there is also a balloon status. Clicking on the icon
- gives a menu from which properties, etc, can be set and
- the full gui is available under "Advanced". To be
- fully functional, the gui mode should be "start"
- (the default).
-
- Note that tray or icon mode will imply the -forever
- x11vnc option (if the x11vnc server is started along
- with the gui) unless -connect or -connect_or_exit has
- been specified. So x11vnc (and the tray/icon gui)
- will wait for more connections after the first client
- disconnects. If you want only one viewer connection
- include the -once option.
-
- For "icon" the gui just a small standalone window.
- For "tray" it will attempt to embed itself in the
- "system tray" if possible. If "=setpass" is appended the
-n
- at startup the X11 user will be prompted to set the
- VNC session password. If =<hexnumber> is appended
- that icon will attempt to embed itself in the window
- given by hexnumber. Use =noadvanced to disable the
- full gui. (To supply more than one, use "+" sign).
- E.g. -gui tray=setpass and -gui icon=0x3600028
-
- Other modes: "full", the default and need not be
- specified. "-gui none", do not show a gui, useful
- to override a ~/.x11vncrc setting, etc.
-
- 5) When "geom=+X+Y" is specified, that geometry
- is passed to the gui toplevel. This is the icon in
- icon/tray mode, or the full gui otherwise. You can
- also specify width and height, i.e. WxH+X+Y, but it
- is not recommended. In "tray" mode the geometry is
- ignored unless the system tray manager does not seem
- to be running. One could imagine using something like
- "-gui tray,geom=+4000+4000" with a display manager
- to keep the gui invisible until someone logs in...
-
- More icon tricks, "icon=minimal" gives an icon just
- with the VNC display number. You can also set the font
- with "iconfont=...". The following could be useful:
- "-gui icon=minimal,iconfont=5x8,geom=24x10+0-0"
-
- General examples of the -gui option: "x11vnc -gui",
- "x11vnc -gui ez" "x11vnc -gui localhost:10",
- "x11vnc -gui conn,host:0", "x11vnc -gui tray,ez"
- "x11vnc -gui tray=setpass"
-
- If you do not intend to start x11vnc from the gui
- (i.e. just remote control an existing one), then the
- gui process can run on a different machine from the
- x11vnc server as long as X permissions, etc. permit
- communication between the two.
-
- FONTS: On some systems the tk fonts can be too small,
- jagged, or otherwise unreadable. There are 4 env vars
- you can set to be the tk font you prefer:
-
- X11VNC_FONT_BOLD main font for menus and buttons.
- X11VNC_FONT_FIXED font for fixed width text.
-
- X11VNC_FONT_BOLD_SMALL tray icon font.
- X11VNC_FONT_REG_SMALL tray icon menu font.
-
- The last two only apply for the tray icon mode.
-
- Here are some examples:
-
- -env X11VNC_FONT_BOLD='Helvetica -16 bold'
- -env X11VNC_FONT_FIXED='Courier -14'
- -env X11VNC_FONT_REG_SMALL='Helvetica -12'
-
- You can put the lines like the above (without the
- quotes) in your ~/.x11vncrc file to avoid having to
- specify them on the x11vnc command line.
-
--remote command Remotely control some aspects of an already running
- x11vnc server. "-R" and "-r" are aliases for
- "-remote". After the remote control command is
- sent to the running server the 'x11vnc -remote ...'
- x11vnc command exits. You can often use the -query
- command (see below) to see if the x11vnc server
- processed your -remote command.
-
- The default communication channel is that of X
- properties (specifically X11VNC_REMOTE), and so this
- command must be run with correct settings for DISPLAY
- and possibly XAUTHORITY to connect to the X server
- and set the property. Alternatively, use the -display
- and -auth options to set them to the correct values.
- The running server cannot use the -novncconnect option
- because that disables the communication channel.
- See below for alternate channels.
-
- For example: 'x11vnc -remote stop' (which is the same as
- 'x11vnc -R stop') will close down the x11vnc server.
- 'x11vnc -R shared' will enable shared connections, and
- 'x11vnc -R scale:3/4' will rescale the desktop.
-
- To use a different name for the X11 property (e.g. to
- have separate communication channels for multiple
- x11vnc's on the same display) set the X11VNC_REMOTE
- environment variable to the string you want, for
- example: -env X11VNC_REMOTE=X11VNC_REMOTE_12345
- Both sides of the channel must use the same unique name.
-
- To run a bunch of commands in a sequence use something
- like: x11vnc -R 'script:firstcmd;secondcmd;...'
-
- Use x11vnc -R script:file=/path/to/file to read commands
- from a file (can be multi-line and use the comment '#'
- character in the normal way. The ';' separator must
- still be used to separate each command.)
-
- To not try to contact another x11vnc process and instead
- just run the command (or query) directly, prefix the
- command with the string "DIRECT:"
-
- The following -remote/-R commands are supported:
-
- stop terminate the server, same as "quit"
- "exit" or "shutdown".
- ping see if the x11vnc server responds.
- return is: ans=ping:<display>
- ping:mystring as above, but use your own unique string
-.
- return is: ans=ping:mystring:<xdisplay>
- blacken try to push a black fb update to all
- clients (due to timings a client
- could miss it). Same as "zero", also
- "zero:x1,y1,x2,y2" for a rectangle.
- refresh send the entire fb to all clients.
- reset recreate the fb, polling memory, etc.
- id:windowid set -id window to "windowid". empty
- or "root" to go back to root window
- sid:windowid set -sid window to "windowid"
- id_cmd:cmd cmds: raise, lower, map, unmap, iconify,
- move:dXdY, resize:dWdH, geom:WxH+X+Y. dX
- dY, dW, and dH must have a leading "+"
- or "-" e.g.: move:-30+10 resize:+20+35
- also: wm_delete, wm_name:string and
- icon_name:string. Also id_cmd:win=N:cmd
- waitmapped wait until subwin is mapped.
- nowaitmapped do not wait until subwin is mapped.
- clip:WxH+X+Y set -clip mode to "WxH+X+Y"
- flashcmap enable -flashcmap mode.
- noflashcmap disable -flashcmap mode.
- shiftcmap:n set -shiftcmap to n.
- notruecolor enable -notruecolor mode.
- truecolor disable -notruecolor mode.
- overlay enable -overlay mode (if applicable).
- nooverlay disable -overlay mode.
- overlay_cursor in -overlay mode, enable cursor drawing.
- overlay_nocursor disable cursor drawing. same as
- nooverlay_cursor.
- 8to24 enable -8to24 mode (if applicable).
- no8to24 disable -8to24 mode.
- 8to24_opts:str set the -8to24 opts to "str".
- 24to32 enable -24to32 mode (if applicable).
- no24to32 disable -24to32 mode.
- visual:vis set -visual to "vis"
- scale:frac set -scale to "frac"
- scale_cursor:f set -scale_cursor to "f"
- viewonly enable -viewonly mode.
- noviewonly disable -viewonly mode.
- shared enable -shared mode.
- noshared disable -shared mode.
- forever enable -forever mode.
- noforever disable -forever mode.
- timeout:n reset -timeout to n, if there are
- currently no clients, exit unless one
- connects in the next n secs.
- tightfilexfer enable filetransfer for NEW clients.
- notightfilexfer disable filetransfer for NEW clients.
- ultrafilexfer enable filetransfer for clients.
- noultrafilexfer disable filetransfer for clients.
- rfbversion:n.m set -rfbversion for new clients.
- http enable http client connections.
- nohttp disable http client connections.
- deny deny any new connections, same as "lock"
- nodeny allow new connections, same as "unlock"
- avahi enable avahi service advertising.
- noavahi disable avahi service advertising.
- mdns enable avahi service advertising.
- nomdns disable avahi service advertising.
- zeroconf enable avahi service advertising.
- nozeroconf disable avahi service advertising.
- connect:host do reverse connection to host, "host"
- may be a comma separated list of hosts
- or host:ports. See -connect. Passwords
- required as with fwd connections.
- See X11VNC_REVERSE_CONNECTION_NO_AUTH=1
- disconnect:host disconnect any clients from "host"
- same as "close:host". Use host
- "all" to close all current clients.
- If you know the client internal hex ID,
- e.g. 0x3 (returned by "-query clients"
- and RFB_CLIENT_ID) you can use that too.
- proxy:host:port set reverse connection proxy (empty to
- disable).
- allowonce:host For the next connection only, allow
- connection from "host". In -ssl mode
- two connections are allowed (i.e. Fetch
- Cert) unless X11VNC_NO_SSL_ALLOW_TWICE=1
- allow:hostlist set -allow list to (comma separated)
- "hostlist". See -allow and -localhost.
- Do not use with -allow /path/to/file
- Use "+host" to add a single host, and
- use "-host" to delete a single host
- localhost enable -localhost mode
- nolocalhost disable -localhost mode
- listen:str set -listen to str, empty to disable.
- noipv6 enable -noipv6 mode.
- ipv6 disable -noipv6 mode.
- noipv4 enable -noipv4 mode.
- ipv4 disable -noipv4 mode.
- 6 enable -6 IPv6 listening mode.
- no6 disable -6 IPv6 listening mode.
- lookup disable -nolookup mode.
- nolookup enable -nolookup mode.
- lookup disable -nolookup mode.
- input:str set -input to "str", empty to disable.
- grabkbd enable -grabkbd mode.
- nograbkbd disable -grabkbd mode.
- grabptr enable -grabptr mode.
- nograbptr disable -grabptr mode.
- grabalways enable -grabalways mode.
- nograbalways disable -grabalways mode.
- grablocal:n set -grablocal to n.
- client_input:str set the K, M, B -input on a per-client
- basis. select which client as for
- disconnect, e.g. client_input:host:MB
- or client_input:0x2:K
- accept:cmd set -accept "cmd" (empty to disable).
- afteraccept:cmd set -afteraccept (empty to disable).
- gone:cmd set -gone "cmd" (empty to disable).
- noshm enable -noshm mode.
- shm disable -noshm mode (i.e. use shm).
- flipbyteorder enable -flipbyteorder mode, you may need
- to set noshm for this to do something.
- noflipbyteorder disable -flipbyteorder mode.
- onetile enable -onetile mode. (you may need to
- set shm for this to do something)
- noonetile disable -onetile mode.
- solid enable -solid mode
- nosolid disable -solid mode.
- solid_color:color set -solid color (and apply it).
- blackout:str set -blackout "str" (empty to disable).
- See -blackout for the form of "str"
- (basically: WxH+X+Y,...)
- Use "+WxH+X+Y" to append a single
- rectangle use "-WxH+X+Y" to delete one
- xinerama enable -xinerama mode. (if applicable)
- noxinerama disable -xinerama mode.
- xtrap enable -xtrap input mode(if applicable)
- noxtrap disable -xtrap input mode.
- xrandr enable -xrandr mode. (if applicable)
- noxrandr disable -xrandr mode.
- xrandr_mode:mode set the -xrandr mode to "mode".
- rotate:mode set the -rotate mode to "mode".
- padgeom:WxH set -padgeom to WxH (empty to disable)
- If WxH is "force" or "do" the padded
- geometry fb is immediately applied.
- quiet enable -quiet mode.
- noquiet disable -quiet mode.
- modtweak enable -modtweak mode.
- nomodtweak enable -nomodtweak mode.
- xkb enable -xkb modtweak mode.
- noxkb disable -xkb modtweak mode.
- capslock enable -capslock mode.
- nocapslock disable -capslock mode.
- skip_lockkeys enable -skip_lockkeys mode.
- noskip_lockkeys disable -skip_lockkeys mode.
- skip_keycodes:str enable -xkb -skip_keycodes "str".
- sloppy_keys enable -sloppy_keys mode.
- nosloppy_keys disable -sloppy_keys mode.
- skip_dups enable -skip_dups mode.
- noskip_dups disable -skip_dups mode.
- add_keysyms enable -add_keysyms mode.
- noadd_keysyms stop adding keysyms. those added will
- still be removed at exit.
- clear_mods enable -clear_mods mode and clear them.
- noclear_mods disable -clear_mods mode.
- clear_keys enable -clear_keys mode and clear them.
- noclear_keys disable -clear_keys mode.
- clear_locks do the clear_locks action.
- clear_all do the clear_all action.
- keystate have x11vnc print current keystate.
- remap:str set -remap "str" (empty to disable).
- See -remap for the form of "str"
- (basically: key1-key2,key3-key4,...)
- Use "+key1-key2" to append a single
- keymapping, use "-key1-key2" to delete.
- norepeat enable -norepeat mode.
- repeat disable -norepeat mode.
- nofb enable -nofb mode.
- fb disable -nofb mode.
- bell enable bell (if supported).
- nobell disable bell.
- sendbell ring the bell now.
- nosel enable -nosel mode.
- sel disable -nosel mode.
- noprimary enable -noprimary mode.
- primary disable -noprimary mode.
- nosetprimary enable -nosetprimary mode.
- setprimary disable -nosetprimary mode.
- noclipboard enable -noclipboard mode.
- clipboard disable -noclipboard mode.
- nosetclipboard enable -nosetclipboard mode.
- setclipboard disable -nosetclipboard mode.
- seldir:str set -seldir to "str"
- resend_cutbuffer resend the most recent CUTBUFFER0 copy
- resend_clipboard resend the most recent CLIPBOARD copy
- resend_primary resend the most recent PRIMARY copy
- cursor:mode enable -cursor "mode".
- show_cursor enable showing a cursor.
- noshow_cursor disable showing a cursor. (same as
- "nocursor")
- cursor_drag enable cursor changes during drag.
- nocursor_drag disable cursor changes during drag.
- arrow:n set -arrow to alternate n.
- xfixes enable xfixes cursor shape mode.
- noxfixes disable xfixes cursor shape mode.
- alphacut:n set -alphacut to n.
- alphafrac:f set -alphafrac to f.
- alpharemove enable -alpharemove mode.
- noalpharemove disable -alpharemove mode.
- alphablend disable -noalphablend mode.
- noalphablend enable -noalphablend mode.
- cursorshape disable -nocursorshape mode.
- nocursorshape enable -nocursorshape mode.
- cursorpos disable -nocursorpos mode.
- nocursorpos enable -nocursorpos mode.
- xwarp enable -xwarppointer mode.
- noxwarp disable -xwarppointer mode.
- always_inject enable -always_inject mode.
- noalways_inject disable -always_inject mode.
- buttonmap:str set -buttonmap "str", empty to disable
- dragging disable -nodragging mode.
- nodragging enable -nodragging mode.
- ncache reenable -ncache mode.
- noncache disable -ncache mode.
- ncache_size:n set -ncache size to n.
- ncache_cr enable -ncache_cr mode.
- noncache_cr disable -ncache_cr mode.
- ncache_no_moveraise enable no_moveraise mode.
- noncache_no_moveraise disable no_moveraise mode.
- ncache_no_dtchange enable ncache_no_dtchange mode.
- noncache_no_dtchange disable ncache_no_dtchange mode.
- ncache_old_wm enable ncache_old_wm mode.
- noncache_old_wm disable ncache_old_wm mode.
- ncache_no_rootpixmap enable ncache_no_rootpixmap.
- noncache_no_rootpixmap disable ncache_no_rootpixmap.
- ncache_reset_rootpixmap recheck the root pixmap, ncrp
- ncache_keep_anims enable ncache_keep_anims.
- noncache_keep_anims disable ncache_keep_anims.
- ncache_pad:n set -ncache_pad to n.
- wireframe enable -wireframe mode. same as "wf"
- nowireframe disable -wireframe mode. same as "nowf"
- wireframe:str enable -wireframe mode string.
- wireframe_mode:str enable -wireframe mode string.
- wireframelocal enable wireframelocal. same as "wfl"
- nowireframe disable wireframelocal. same as "nowfl"
- wirecopyrect:str set -wirecopyrect string. same as "wcr:
-"
- scrollcopyrect:str set -scrollcopyrect string. same "scr
-"
- noscrollcopyrect disable -scrollcopyrect mode. "noscr"
- scr_area:n set -scr_area to n
- scr_skip:list set -scr_skip to "list"
- scr_inc:list set -scr_inc to "list"
- scr_keys:list set -scr_keys to "list"
- scr_term:list set -scr_term to "list"
- scr_keyrepeat:str set -scr_keyrepeat to "str"
- scr_parms:str set -scr_parms parameters.
- fixscreen:str set -fixscreen to "str".
- noxrecord disable all use of RECORD extension.
- xrecord enable use of RECORD extension.
- reset_record reset RECORD extension (if avail.)
- pointer_mode:n set -pointer_mode to n. same as "pm"
- input_skip:n set -input_skip to n.
- allinput enable use of -allinput mode.
- noallinput disable use of -allinput mode.
- input_eagerly enable use of -input_eagerly mode.
- noinput_eagerly disable use of -input_eagerly mode.
- ssltimeout:n set -ssltimeout to n.
- speeds:str set -speeds to str.
- wmdt:str set -wmdt to str.
- debug_pointer enable -debug_pointer, same as "dp"
- nodebug_pointer disable -debug_pointer, same as "nodp"
- debug_keyboard enable -debug_keyboard, same as "dk"
- nodebug_keyboard disable -debug_keyboard, same as "nodk"
- keycode:n inject keystroke 'keycode' (xmodmap -pk)
- keycode:n,down inject 'keycode' (down=0,1)
- keysym:str inject keystroke 'keysym' (number/name)
- keysym:str,down inject 'keysym' (down=0,1)
- ptr:x,y,mask inject pointer event x, y, button-mask
- fakebuttonevent:button,down direct XTestFakeButtonEvent.
- sleep:t sleep floating point time t.
- get_xprop:p get X property named 'p'.
- set_xprop:p:val set X property named 'p' to 'val'.
- p -> id=NNN:p for hex/dec window id.
- wininfo:id get info about X window id. use 'root'
- for root window, use +id for children.
- grab_state get state of pointer and keyboard grab.
- pointer_pos print XQueryPointer x,y cursor position.
- pointer_x print XQueryPointer x cursor position.
- pointer_y print XQueryPointer y cursor position.
- pointer_same print XQueryPointer ptr on same screen.
- pointer_root print XQueryPointer curr ptr rootwin.
- pointer_mask print XQueryPointer button and mods mask
- mouse_x print x11vnc's idea of cursor position.
- mouse_y print x11vnc's idea of cursor position.
- noop do nothing.
- defer:n set -defer to n ms,same as deferupdate:n
- wait:n set -wait to n ms.
- extra_fbur:n set -extra_fbur to n.
- wait_ui:f set -wait_ui factor to f.
- setdefer:n set -setdefer to -2,-1,0,1, or 2.
- wait_bog disable -nowait_bog mode.
- nowait_bog enable -nowait_bog mode.
- slow_fb:f set -slow_fb to f seconds.
- xrefresh:f set -xrefresh to f seconds.
- readtimeout:n set read timeout to n seconds.
- nap enable -nap mode.
- nonap disable -nap mode.
- sb:n set -sb to n s, same as screen_blank:n
- fbpm disable -nofbpm mode.
- nofbpm enable -nofbpm mode.
- dpms disable -nodpms mode.
- nodpms enable -nodpms mode.
- forcedpms enable -forcedpms mode.
- noforcedpms disable -forcedpms mode.
- clientdpms enable -clientdpms mode.
- noclientdpms disable -clientdpms mode.
- noserverdpms enable -noserverdpms mode.
- serverdpms disable -noserverdpms mode.
- noultraext enable -noultraext mode.
- ultraext disable -noultraext mode.
- chatwindow enable local chatwindow mode.
- nochatwindow disable local chatwindow mode.
- chaton begin chat using local window.
- chatoff end chat using local window.
- xdamage enable xdamage polling hints.
- noxdamage disable xdamage polling hints.
- xd_area:A set -xd_area max pixel area to "A"
- xd_mem:f set -xd_mem remembrance to "f"
- fs:frac set -fs fraction to "frac", e.g. 0.5
- gaps:n set -gaps to n.
- grow:n set -grow to n.
- fuzz:n set -fuzz to n.
- snapfb enable -snapfb mode.
- nosnapfb disable -snapfb mode.
- rawfb:str set -rawfb mode to "str".
- uinput_accel:f set uinput_accel to f.
- uinput_thresh:n set uinput_thresh to n.
- uinput_reset:n set uinput_reset to n ms.
- uinput_always:n set uinput_always to 1/0.
- progressive:n set LibVNCServer -progressive slice
- height parameter to n.
- desktop:str set -desktop name to str for new clients
-.
- rfbport:n set -rfbport to n.
- macnosaver enable -macnosaver mode.
- macsaver disable -macnosaver mode.
- macnowait enable -macnowait mode.
- macwait disable -macnowait mode.
- macwheel:n set -macwheel to n.
- macnoswap enable -macnoswap mouse button mode.
- macswap disable -macnoswap mouse button mode.
- macnoresize enable -macnoresize mode.
- macresize disable -macnoresize mode.
- maciconanim:n set -maciconanim to n.
- macmenu enable -macmenu mode.
- macnomenu disable -macmenu mode.
- macuskbd enable -macuskbd mode.
- macnouskbd disable -macuskbd mode.
- httpport:n set -httpport to n.
- httpdir:dir set -httpdir to dir (and enable http).
- enablehttpproxy enable -enablehttpproxy mode.
- noenablehttpproxy disable -enablehttpproxy mode.
- alwaysshared enable -alwaysshared mode.
- noalwaysshared disable -alwaysshared mode.
- (may interfere with other options)
- nevershared enable -nevershared mode.
- nonevershared disable -nevershared mode.
- (may interfere with other options)
- dontdisconnect enable -dontdisconnect mode.
- nodontdisconnect disable -dontdisconnect mode.
- (may interfere with other options)
- debug_xevents enable debugging X events.
- nodebug_xevents disable debugging X events.
- debug_xdamage enable debugging X DAMAGE mechanism.
- nodebug_xdamage disable debugging X DAMAGE mechanism.
- debug_wireframe enable debugging wireframe mechanism.
- nodebug_wireframe disable debugging wireframe mechanism.
- debug_scroll enable debugging scrollcopy mechanism.
- nodebug_scroll disable debugging scrollcopy mechanism.
- debug_tiles enable -debug_tiles
- nodebug_tiles disable -debug_tiles
- debug_grabs enable -debug_grabs
- nodebug_grabs disable -debug_grabs
- debug_sel enable -debug_sel
- nodebug_sel disable -debug_sel
- debug_ncache enable -debug_ncache
- nodebug_ncache disable -debug_ncache
- dbg enable -dbg crash shell
- nodbg disable -dbg crash shell
-
- noremote disable the -remote command processing,
- it cannot be turned back on.
-
- bcx_xattach:str This remote control command is for
- use with the BARCO xattach program or the x2x program.
- Both of these programs are for 'pointer and keyboard'
- sharing between separate X displays. In general the
- two displays are usually nearby, e.g. on the same desk,
- and this allows the user to share a single pointer and
- keyboard between them. The user moves the mouse to
- an edge and then the mouse pointer appears to 'jump'
- to the other display screen. Thus it emulates what a
- single X server would do for two screens (e.g. :0.0 and
- :0.1) The illusion of a single Xserver with multiple
- screens is achieved by forwarding events to the 2nd
- one via the XTEST extension.
-
- What the x11vnc bcx_xattach command does is to perform
- some pointer movements to try to INDUCE xattach/x2x
- to 'jump' to the other display. In what follows the
- 'master' display refers to the one that when it has
- 'focus' it is basically doing nothing besides watching
- for the mouse to go over an edge. The 'slave'
- display refers to the one to which the mouse and
- keyboard is redirected to once an edge in the master
- has been crossed. Note that the x11vnc executing the
- bcx_xattach command MUST be the one connected to the
- *master* display.
-
- Also note that when input is being redirected (via
- XTEST) from the master display to the slave display,
- the master display's pointer and keyboard are *grabbed*
- by xattach/x2x. x11vnc can use this info to verify that
- the master/slave mode change has taken place correctly.
- If you specify the "ifneeded" option (see below)
- and the initial grab state is that of the desired
- final state, then no pointer movements are injected
- and "DONE,GRAB_OK" is returned.
-
- "str" must contain one of "up", "down", "left",
- or "right" to indicate the direction of the 'jump'.
- "str" must also contain one of "master_to_slave"
- or "slave_to_master" to indicate the type of mode
- change induced by the jump. Use "M2S" and "S2M"
- as shorter aliases.
-
- "str" may be a "+" separated list of additional
- tuning options. The "shift=n" option indicates an
- offset shift position away from (0,0) (default 20).
- "final=x+y" specifies the final position of the cursor
- at the end of the normal move sequence; default 30+30.
- "extra_move=x+y" means to do one more pointer move
- after "final" to x+y. "dt=n" sets the sleep time
- in milliseconds between pointer moves (default: 40ms)
- "retry=n" specifies the maximum number of retries if
- the grab state change fails. "ifneeded" means to not
- apply the pointer movements if the initial grab state is
- that of the desired final state. "nograbcheck" means
- to not check if the grab state changed as expected and
- only apply the pointer movements (default is to check
- the grab states.)
-
- If you do not specify "up", etc., to bcx_xattach
- nothing will be attempted and the command returns
- the string FAIL,NO_DIRECTION_SPECIFIED. If you do
- not specify "master_to_slave" or "M2S", etc., to
- bcx_xattach nothing will be attempted and the command
- returns the string FAIL,NO_MODE_CHANGE_SPECIFIED.
-
- Otherwise, the returned string will contain "DONE".
- It will be "DONE,GRAB_OK" if the grab state changed
- as expected (or if "ifneeded" was supplied and
- the initial grab state was already the desired
- one.) If the initial grab state was incorrect,
- but the final grab state was correct then it is
- "DONE,GRAB_FAIL_INIT". If the initial grab state
- was correct, but the final grab state was incorrect
- then it is "DONE,GRAB_FAIL_FINAL". If both are
- incorrect it will be "DONE,GRAB_FAIL". Under grab
- failure the string will be followed by ":p1,k1-p2,k2"
- where p1,k1 indicates the initial pointer and keyboard
- grab states and p2,k2 the final ones. If GRAB_FAIL or
- GRAB_FAIL_FINAL occurs, the action will be retried up
- to 3 times; trying to reset the state and sleeping a
- bit between each try. Set retry=n to adjust the number
- of retries, zero to disable retries.
-
- Examples:
- -R bcx_xattach:down+M2S
- -R bcx_xattach:up+S2M
- -R bcx_xattach:up+S2M+nograbcheck+dt=30
- -R bcx_xattach:down+M2S+extra_move=100+100
-
- or use -Q instead of -R to retrieve the result text.
-
- End of the bcx_xattach:str description.
-
- The vncconnect(1) command from standard VNC
- distributions may also be used if string is prefixed
- with "cmd=" E.g. 'vncconnect cmd=stop'. Under some
- circumstances xprop(1) can used if it supports -set
- (see the FAQ).
-
- If "-connect /path/to/file" has been supplied to the
- running x11vnc server then that file can be used as a
- communication channel (this is the only way to remote
- control one of many x11vnc's polling the same X display)
- Simply run: 'x11vnc -connect /path/to/file -remote ...'
- or you can directly write to the file via something
- like: "echo cmd=stop > /path/to/file", etc.
-
--query variable Like -remote, except just query the value of
- "variable". "-Q" is an alias for "-query".
- Multiple queries can be done by separating variables
- by commas, e.g. -query var1,var2. The results come
- back in the form ans=var1:value1,ans=var2:value2,...
- to the standard output. If a variable is read-only,
- it comes back with prefix "aro=" instead of "ans=".
-
- Some -remote commands are pure actions that do not make
- sense as variables, e.g. "stop" or "disconnect", in
- these cases the value returned is "N/A". To direct a
- query straight to the X11VNC_REMOTE property or connect
- file use "qry=..." instead of "cmd=..."
-
- ans= stop quit exit shutdown ping resend_cutbuffer
- resend_clipboard resend_primary blacken zero refresh
- reset close disconnect id_cmd id sid waitmapped
- nowaitmapped clip flashcmap noflashcmap shiftcmap
- truecolor notruecolor overlay nooverlay overlay_cursor
- overlay_yescursor nooverlay_nocursor nooverlay_cursor
- nooverlay_yescursor overlay_nocursor 8to24 no8to24
- 8to24_opts 24to32 no24to32 visual scale scale_cursor
- viewonly noviewonly shared noshared forever noforever
- once timeout tightfilexfer notightfilexfer ultrafilexfer
- noultrafilexfer rfbversion deny lock nodeny unlock avahi
- mdns zeroconf noavahi nomdns nozeroconf connect proxy
- allowonce allow noipv6 ipv6 noipv4 ipv4 no6 6 localhost
- nolocalhost listen lookup nolookup accept afteraccept
- gone shm noshm flipbyteorder noflipbyteorder onetile
- noonetile solid_color solid nosolid blackout xinerama
- noxinerama xtrap noxtrap xrandr noxrandr xrandr_mode
- rotate padgeom quiet q noquiet modtweak nomodtweak xkb
- noxkb capslock nocapslock skip_lockkeys noskip_lockkeys
- skip_keycodes sloppy_keys nosloppy_keys skip_dups
- noskip_dups add_keysyms noadd_keysyms clear_mods
- noclear_mods clear_keys noclear_keys clear_all
- clear_locks keystate remap repeat norepeat fb nofb bell
- nobell sendbell sel nosel primary noprimary setprimary
- nosetprimary clipboard noclipboard setclipboard
- nosetclipboard seldir cursorshape nocursorshape
- cursorpos nocursorpos cursor_drag nocursor_drag cursor
- show_cursor noshow_cursor nocursor arrow xfixes noxfixes
- xdamage noxdamage xd_area xd_mem alphacut alphafrac
- alpharemove noalpharemove alphablend noalphablend
- xwarppointer xwarp noxwarppointer noxwarp always_inject
- noalways_inject buttonmap dragging nodragging ncache_cr
- noncache_cr ncache_no_moveraise noncache_no_moveraise
- ncache_no_dtchange noncache_no_dtchange
- ncache_no_rootpixmap noncache_no_rootpixmap
- ncache_reset_rootpixmap ncrp ncache_keep_anims
- noncache_keep_anims ncache_old_wm noncache_old_wm
- ncache_pad ncache noncache ncache_size debug_ncache
- nodebug_ncache wireframe_mode wireframe wf nowireframe
- nowf wireframelocal wfl nowireframelocal nowfl
- wirecopyrect wcr nowirecopyrect nowcr scr_area
- scr_skip scr_inc scr_keys scr_term scr_keyrepeat
- scr_parms scrollcopyrect scr noscrollcopyrect
- noscr fixscreen noxrecord xrecord reset_record
- pointer_mode pm input_skip allinput noallinput
- input_eagerly noinput_eagerly input grabkbd nograbkbd
- grabptr nograbptr grabalways nograbalways grablocal
- client_input ssltimeout speeds wmdt debug_pointer dp
- nodebug_pointer nodp debug_keyboard dk nodebug_keyboard
- nodk keycode keysym ptr fakebuttonevent sleep get_xprop
- set_xprop wininfo bcx_xattach deferupdate defer
- setdefer extra_fbur wait_ui wait_bog nowait_bog
- slow_fb xrefresh wait readtimeout nap nonap sb
- screen_blank fbpm nofbpm dpms nodpms clientdpms
- noclientdpms forcedpms noforcedpms noserverdpms
- serverdpms noultraext ultraext chatwindow nochatwindow
- chaton chatoff fs gaps grow fuzz snapfb nosnapfb
- rawfb uinput_accel uinput_thresh uinput_reset
- uinput_always progressive rfbport http nohttp httpport
- httpdir enablehttpproxy noenablehttpproxy alwaysshared
- noalwaysshared nevershared noalwaysshared dontdisconnect
- nodontdisconnect desktop debug_xevents nodebug_xevents
- debug_xevents debug_xdamage nodebug_xdamage
- debug_xdamage debug_wireframe nodebug_wireframe
- debug_wireframe debug_scroll nodebug_scroll debug_scroll
- debug_tiles dbt nodebug_tiles nodbt debug_tiles
- debug_grabs nodebug_grabs debug_sel nodebug_sel dbg
- nodbg macnosaver macsaver nomacnosaver macnowait macwait
- nomacnowait macwheel macnoswap macswap nomacnoswap
- macnoresize macresize nomacnoresize maciconanim macmenu
- macnomenu nomacmenu macuskbd nomacuskbd noremote
-
- aro= noop display vncdisplay icon_mode autoport
- loop loopbg desktopname guess_desktop guess_dbus
- http_url auth xauth users rootshift clipshift scale_str
- scaled_x scaled_y scale_numer scale_denom scale_fac_x
- scale_fac_y scaling_blend scaling_nomult4 scaling_pad
- scaling_interpolate inetd privremote unsafe safer nocmds
- passwdfile unixpw unixpw_nis unixpw_list ssl ssl_pem
- sslverify stunnel stunnel_pem https httpsredir usepw
- using_shm logfile o flag rmflag rc norc h help V version
- lastmod bg sigpipe threads readrate netrate netlatency
- pipeinput clients client_count pid ext_xtest ext_xtrap
- ext_xrecord ext_xkb ext_xshm ext_xinerama ext_overlay
- ext_xfixes ext_xdamage ext_xrandr rootwin num_buttons
- button_mask mouse_x mouse_y grab_state pointer_pos
- pointer_x pointer_y pointer_same pointer_root
- pointer_mask bpp depth indexed_color dpy_x dpy_y wdpy_x
- wdpy_y off_x off_y cdpy_x cdpy_y coff_x coff_y rfbauth
- passwd viewpasswd
-
--QD variable Just like -query variable, but returns the default
- value for that parameter (no running x11vnc server
- is consulted)
-
--sync By default -remote commands are run asynchronously, that
- is, the request is posted and the program immediately
- exits. Use -sync to have the program wait for an
- acknowledgement from the x11vnc server that command was
- processed (somehow). On the other hand -query requests
- are always processed synchronously because they have
- to wait for the answer.
-
- Also note that if both -remote and -query requests are
- supplied on the command line, the -remote is processed
- first (synchronously: no need for -sync), and then
- the -query request is processed in the normal way.
- This allows for a reliable way to see if the -remote
- command was processed by querying for any new settings.
- Note however that there is timeout of a few seconds
- (see the next paragraph) so if the x11vnc takes longer
- than that to process the requests the requester will
- think that a failure has taken place.
-
- The default is to wait 3.5 seconds. Or if cmd=stop
- only 1.0 seconds. If cmd matches 'script:' then it
- will wait up to 10.0 seconds. Set X11VNC_SYNC_TIMEOUT
- to the number of seconds you want it to wait.
-
--query_retries str If a query fails to get a response from an x11vnc
- server, retry up to n times. "str" is specified as
- n[:t][/match] Optionally the delay between tries may
- be specified by "t" a floating point time (default
- 0.5 seconds.) Note: the response is not checked for
- validity or whether it corresponds to the query sent.
- The query "ping:mystring" may be used to help uniquely
- identify the query. Optionally, a matching string after
- a "/" will be used to check the result text. Up to
- n retries will take place until the matching string is
- found in the output text. If the match string is never
- found the program's exit code is 1; if the match is
- found it exits with 0. Note that there may be stdout
- printed for each retry (i.e. multiple lines printed
- out to stdout.)
- Example: -query_retries 4:1.5/grab_state
-
--remote_prefix str Enable a remote-control communication channel for
- connected VNC clients. str is a non-empty string. If a
- VNC client sends rfbCutText having the prefix "str"
- then the part after it is processed as though it were
- sent via 'x11vnc -remote ...'. If it begins with
- neither 'cmd=' nor 'qry=' then 'qry=' is assumed.
- Any corresponding output text for that remote control
- command is sent back to all client as rfbCutText.
- The returned output is also prefixed with "str".
- Example: -remote_prefix DO_THIS:
-
- Note that enabling -remote_prefix allows the remote
- VNC viewers to run x11vnc -remote commands. Do not
- use this option if they are not to be trusted.
-
--noremote Do not process any remote control commands or queries.
--yesremote Do process remote control commands or queries.
- Default: -yesremote
-
- A note about security wrt remote control commands.
- If someone can connect to the X display and change
- the property X11VNC_REMOTE, then they can remotely
- control x11vnc. Normally access to the X display is
- protected. Note that if they can modify X11VNC_REMOTE
- on the X server, they have enough permissions to also
- run their own x11vnc and thus have complete control
- of the desktop. If the "-connect /path/to/file"
- channel is being used, obviously anyone who can write
- to /path/to/file can remotely control x11vnc. So be
- sure to protect the X display and that file's write
- permissions. See -privremote below.
-
- If you are paranoid and do not think -noremote is
- enough, to disable the X11VNC_REMOTE property channel
- completely use -novncconnect, or use the -safer option
- that shuts many things off.
-
--unsafe A few remote commands are disabled by default
- (currently: id:pick, accept:<cmd>, gone:<cmd>, and
- rawfb:setup:<cmd>) because they are associated with
- running external programs. If you specify -unsafe, then
- these remote-control commands are allowed. Note that
- you can still specify these parameters on the command
- line, they just cannot be invoked via remote-control.
--safer Equivalent to: -novncconnect -noremote and prohibiting
- -gui and the -connect file. Shuts off communcation
- channels.
--privremote Perform some sanity checks and disable remote-control
- commands if it appears that the X DISPLAY and/or
- connectfile can be accessed by other users. Once
- remote-control is disabled it cannot be turned back on.
--nocmds No external commands (e.g. system(3), popen(3), exec(3))
- will be run at all.
--allowedcmds list "list" contains a comma separated list of the only
- external commands that can be run. The full list of
- associated options is:
-
- stunnel, ssl, unixpw, WAIT, zeroconf, id, accept,
- afteraccept, gone, pipeinput, v4l-info, rawfb-setup,
- dt, gui, ssh, storepasswd, passwdfile, custom_passwd,
- findauth, crash.
-
- See each option's help to learn the associated external
- command. Note that the -nocmds option takes precedence
- and disables all external commands.
-
--deny_all For use with -remote nodeny: start out denying all
- incoming clients until "-remote nodeny" is used to
- let them in.
-
-
-
-These options are passed to LibVNCServer:
-
--rfbport port TCP port for RFB protocol
--rfbwait time max time in ms to wait for RFB client
--rfbauth passwd-file use authentication on RFB protocol
- (use 'storepasswd' to create a password file)
--rfbversion 3.x Set the version of the RFB we choose to advertise
--permitfiletransfer permit file transfer support
--passwd plain-password use authentication
- (use plain-password as password, USE AT YOUR RISK)
--deferupdate time time in ms to defer updates (default 40)
--deferptrupdate time time in ms to defer pointer updates (default none)
--desktop name VNC desktop name (default "LibVNCServer")
--alwaysshared always treat new clients as shared
--nevershared never treat new clients as shared
--dontdisconnect don't disconnect existing clients when a new non-shared
- connection comes in (refuse new connection instead)
--httpdir dir-path enable http server using dir-path home
--httpport portnum use portnum for http connection
--enablehttpproxy enable http proxy support
--progressive height enable progressive updating for slow links
--listen ipaddr listen for connections only on network interface with
- addr ipaddr. '-listen localhost' and hostname work too.
-
-libvncserver-tight-extension options:
--disablefiletransfer disable file transfer
--ftproot string set ftp root
-
- Pretty wild huh? Contact me if you have any questions or problems.
-
- Personally, I use:
-x11vnc -rfbauth $HOME/.vnc/passwd -solid