X11vnc

From the x11vnc home page:

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.

1 Setting up x11vnc

1.1 Installation

x11vnc is available in the official repositories.

1.2 Starting

First, start X either by startx or through a manager such as GDM or SLiM. Then, open a terminal and type

$ x11vnc -display :0

Another option is to place the x11vnc line in a script which is called at login.

#!/bin/bash
/usr/bin/x11vnc -nap -wait 50 -noxdamage -passwd PASSWORD -display :0 -forever -o /var/log/x11vnc.log -bg

Note: The password "PASSWORD" above is not secured; anyone who can run ps on the machine will see it. Also note that /var/log/x11vnc.log needs to be created manually and its ownership needs to match that of the user who will run it.

1.2.1 Setting X authority

You may set an X authority file for the VNC server. This is accomplished by using the -auth argument followed by the appropriate file, which will depend on how your X server was started. Generally, assigning an X authority file requires running x11vnc as root.

startx

$ x11vnc -display :0 -auth ~/.Xauthority

If that fails, you may have to run (as root)

$ x11vnc -display :0 -auth /home/USER/.Xauthority

Where USER is the username of the user who is running the X server.

GDM

as root, run

$ x11vnc -display :0 -auth /var/lib/gdm/:0.Xauth

OR see Troubleshooting section below

SLIM

as root, run

$ x11vnc -display :0 -auth /var/run/slim.auth

Warning: This will set up VNC with NO PASSWORD. This means that ANYBODY who has access to the network the computer is on CAN SEE YOUR XSERVER. It is a fairly simple matter to tunnel your VNC connection through SSH to avoid this. Or, simply set a password, as described below.

Note: The password will only encrypt the login process itself. The transmission is still unencrypted[1].

1.2.2 Setting a password

$ mkdir ~/.x11vnc
$ x11vnc -storepasswd password ~/.x11vnc/passwd

To connect using the stored password use the -rfbauth argument and point to the passwd file you created, like so:

$ x11vnc -display :0 -rfbauth ~/.x11vnc/passwd 

Your viewer should prompt for a password when connecting.

1.2.3 Running constantly

By default, x11vnc will accept the first VNC session and shutdown when the session disconnects. In order to avoid that, start x11vnc with the -many argument, like this:

$ x11vnc -many -display :0

To start silently

$ x11vnc -many -display :0 &>/dev/null &

1.3 Accessing

Get a VNC client on another computer, and type in the IP address of the computer running x11vnc. Hit connect, and you should be set.

If you are attempting to access a VNC server / computer (running x11vnc) from outside of its network then you will need to ensure that it has port 5900 forwarded.

2 SSH Tunnel

You need to have SSH installed and configured.

Use the -localhost flag to x11vnc to have it bind to the local interface. Once that is done, you can use SSH to tunnel the port, and then connect to VNC through SSH. (I have not tried this) (confirmed working for me, thanks --bloodniece)

Simple example (from http://www.karlrunge.com/x11vnc/index.html#tunnelling ):

$ ssh -t -p 22 -L 5900:localhost:5900 remote_host 'x11vnc -localhost -display :0'

where remote_host is the host of the user who is running the X server.

Example:

$ ssh -t -p 22 -L 5900:localhost:5900 user@domain.org 'x11vnc -localhost -display :0'

(you will likely have to provide passwords/passphrases to login from your current location into your remote_host Unix account; we assume you have a login account on remote_host and it is running the SSH server)

And then in another terminal window on your current machine run the command:

$ vncviewer localhost:0

Note: If you have problems to access, you can to solve it entering with this method:

ssh -t -p 22 -L 5900:localhost:5900 user@domain 'su -c "x11vnc -localhost -display :0 -auth guess"'

In this case, you need to know the root password computer that you access.

2.1 Troubleshooting

1. You can check your ip address and make sure port 5900 is forwarded by visiting this website.

2. Tested only on GNOME + GDM

If you cannot start the tunnel, and get error like XOpenDisplay(":0") failed, Check if you have a ~/.Xauthority directory. If that does not exist, You can create one easily (Actually a symlink to actual one) by running command given below as normal user NOT ROOT OR USING Sudo as below:

$ ln -sv `dirname $(xauth info | awk '/Authority file/{print $3}')` /home/`whoami`/.Xauthority

then try above tunneling example and it should work fine. Further if you want this to be automatically done each time Xorg is restarted, create the Xprofile file & make is executable as below

$ ln -sf `dirname $(xauth info | awk '/Authority file/{print $3}')` /home/[ENTER_USERNAME_HERE]/.Xauthority

3. GNOME 3 and x11vnc

If you are using GNOME 3 and x11vnc and you get the following errors

*** XOpenDisplay failed (:0) 

*** x11vnc was unable to open the X DISPLAY: ":0", it cannot continue.

Try running x11vnc like

$ x11vnc -noxdamage -many -display :0 -auth /var/run/gdm/`sudo ls /var/run/gdm | grep \`whoami\``/database -forever -bg

Please update if this works / not works for any other display manager or desktop environment.

3 Acknowledgement

This wiki article is based on ArchWiki. We may have removed non-FSDG bits from it.