How can I set up x11vnc to start on boot, with lightdm?

Question

I have an X server all configured and running with LightDM and GNOME desktop. I have x11vnc installed to access the X server. I open a terminal in GNOME and run x11vnc. This gives me VNC access to the real X server, however I would like to start it automatically. I could put x11vnc in ~/.xprofile to start in after I log in on LightDM, but what I would prefer is to start it immidiately after LightDM is started so that when I log in on VNC, I can see the LightDM prompt. How would I go about doing this?

Answer 1

You can do this by adding a systemd service to start the x11vnc server After= LightDM is started. Ensure that the service is run under user lightdm so that you don't get pesky XAuthority No protocol specified errors.

/etc/systemd/system/[email protected]:

[Unit]
Description=Remote desktop service (VNC)
After=display-manager.service

[Service]
Type=simple
User=lightdm
ExecStart=/usr/bin/x11vnc -display %i                      
Restart=always
RestartSec=3

[Install]
WantedBy=graphical.target

After=display-manager.service tells systemd that the display manager (LightDM) needs to be running before this service can be started.

Type=simple says that the process is non-forking, the command under ExecStart stays running for the duration of the VNC server's life.

User=lightdm says that the process under ExecStart should be run by user lightdm, a system user whose purpose is to run X clients for the duration of the LightDM login prompt. This user owns the X server, so in order to have applications run in the login prompt, you need to run them as this user.

ExecStart=/usr/bin/x11vnc -display %i is the command to run when this service is activated, it says to start x11vnc on display %i, which is referring to whatever comes after the "@" symbol when you start the service.

Restart=always says that whenever the service fails to start, try again.

RestartSec=3 says to wait 3 seconds each time you retry.

WantedBy=graphical.target says to run the service whenever systemd brings up the graphical system (legacy runlevel 5).

To load the unit (make systemd "see" it), run the command

# systemctl daemon-reload

To enable it (make it start on boot), run the command

# systemctl enable x11vnc@<your-$DISPLAY-here>

where <your-$DISPLAY-here> is the X display that you want to give VNC access (usually :0)
To start it, run the command

# systemctl start x11vnc@<your-$DISPLAY-here>

Ditto about the <your-$DISPLAY-here>.

Note that you can run multiple independent services under the same unit file, by passing different displays after the "@". For example, you could run multiple VNC servers on X displays :0, :1, and :2, on ports 5900, 5901, and 5902 with x11vnc@:0, x11vnc@:1, and x11vnc@:2.