How to run GUI application in a rootless docker container?

Question

When I run docker run -it --net=host -e DISPLAY=$DISPLAY <image> and xhost + on my host device, the gui applications in the docker container works well. However, when it comes to rootless dockerd (with env DOCKER_HOST=unix://$XDG_RUNTIME_DIR/docker.sock when using docker cli), the gui applications do not work and prompts

Unable to init server: Could not connect: Connection refused
Error: cannot open display: :0

So what is the difference between root and rootless docker container when connecting to the host display and how to use gui in rootless docker containers?

Answer 1

In rootless Docker, the host machine cannot be reached even if you use --net=host.

Rootless Mode Known limitations:

Host network (docker run --net=host) is also namespaced inside RootlessKit.

You can display with sharing XServer socket.

docker run -it --volume=/tmp/.X11-unix/:/tmp/.X11-unix/ -e DISPLAY=$DISPLAY <image>

There is no need to xhost +, because the UID in the rootless container is mapped to the docker execution user on the host.