Run X GUI Applications in Docker #docker #cli

docker_x_gui.md

Run X GUI Applications in Docker

docker run -it --rm \
  --env="DISPLAY=$DISPLAY" \
  --volume="$HOME/.Xauthority:/root/.Xauthority:ro" \
  --net=host \
  container

The above runs a Docker container with:

1. Sets $DISPLAY environment variable to be :0 which is short for unix:0 (we do this with $DISPLAY)
2. Mounts the file ~/.Xauthority into the container at /root because the user inside the container is usually root.
3. Propagates the host network space into the container, because the X client must be able to contact the X unix domain socket.
4. The usage of -it is for enabling interactive and allocating a pseudo-tty.
5. The usage of --rm is to ensure that the container is removed when the process shutsdown.

On Linux, X clients will try to connect to the abstract unix domain socket with the name /tmp/.X11-unix/X0. Note that X0 is due to :0.

This is why we don't need to mount the /tmp/.X11-unix/X0 into the container. However on non-Linux, you may need to mount that socket as well.

The ~/.Xauthority is intended for the GUI application use your own credentials to connect to the X server.

When using Qt, it will try to use the MIT Shared Memory Extension. This requires either one of the 2 options:

• --env='QT_X11_NO_MITSHM=1' to prevent Qt from trying to use the MIT Shared Memory Extension.
• --ipc=host which adds the host's IPC namespace into the container

Note that if the HOME is not set inside container then you need this:

docker run -it --rm \
  --env="DISPLAY=$DISPLAY" \
  --volume="$HOME/.Xauthority:/.Xauthority:ro" \
  --net=host \
  container

This is because if HOME is not set, then the .Xauthority will be looked up at /.

Just use x11docker in the future!