Using VNCserver + GUI application + Virtual Display in Docker container

Question

I would like to run firefox (or any graphical application) inside docker container.

My requirement: When I start the container, I should be creating a virtual display, starting VNC server and then the GUI application. This means after the container is successfully started, I can connect to the GUI application running inside the container via VNC client. When I close the application, the container should automatically stop.

Attempt 1: I started with the example here https://hub.docker.com/r/devopsil/vnc-firefox/~/dockerfile/ In this example the developer starts the vnc server via CMD and keeps it running forever. He puts the firefox as part of .rc file so it starts when the container starts. If you connect via VNC client, you can see firefox and as expected closing firefox or disconnecting the VNC session does not stop the container.

Attempt 2: I tuned the Dockerfile as follows. Changed only the last line (replaced CMD with ENTRYPOINT and removed the “forever” flag”)

ENTRYPOINT ["/usr/bin/x11vnc", "-usepw", "-create"]

Rebuilding and running the container “docker run --rm -p 5900 ” had a different behaviour now: container starts, connection via VNC client worked, firefox opened after a few seconds (wait after the message "extension RANDR missing on display :20") and the container stopped automatically after closing the vnc connection.

Attempt 3: Then I created a bash script to start the vncserver and firefox and changed the Dockerfile to copy this script file inside the image and made the script as the entry point. But I got the error similar to “Display variable not set”

#!/bin/bash
/usr/bin/x11vnc -forever -usepw -create &
firefox

Attempt 4: So I passed the DISPLAY variable via the docker run command but then the error is cannot open display.

Question: I don’t know how to like the virtual display created by the vncserver flag “-create” to the firefox. Please let me know what would be best way to start the GUI application when the container starts and automatically stop the container when the GUI application is closed. I believe the ENTRYPOINT in dockerfile should be set to firefox. Thanks for your help.

I have seen this https://blog.jessfraz.com/post/docker-containers-on-the-desktop/ but this is of no use to me as I want to access the application remotely via VNC.

Answer 1

I managed to found the solution:

Changed the script in Attempt 3 above as follows worked

!/bin/bash

Xvfb :1 -screen 0 800x600x16 &
/usr/bin/x11vnc -display :1.0 -usepw &
DISPLAY=:1.0
export DISPLAY
firefox

Cheers.

Answer 2

I'm using the following Bash function:

# Configure virtual display and wine.
# Usage: set_display
set_display() {
  export DISPLAY=${DISPLAY:-:0} # Select screen 0 by default.
  xdpyinfo &>/dev/null && return
  if command -v x11vnc &>/dev/null; then
    ! pgrep -a x11vnc && x11vnc -bg -forever -nopw -quiet -display WAIT$DISPLAY &
  fi
  ! pgrep -a Xvfb && Xvfb $DISPLAY -screen 0 1024x768x16 &
  sleep 1
  if command -v fluxbox &>/dev/null; then
    ! pgrep -a fluxbox && fluxbox 2>/dev/null &
  fi
  echo "IP: $(hostname -I) ($(hostname))"
}

Then source the file and call set_display. Consider configuring the password via -usepw.

I'm using it in the following Docker project (check .funcs.cmds.inc.sh).

Check also: How to make Xvfb display visible?