TL;DR-Version:

run: $ sudo pacman -S xorg-server-xephyr or $ sudo apt-get install xserver-xephyr

run: $ Xephyr :1 -ac -br -screen 1024x768 -resizeable -reset -terminate &

run: bash $ docker run -it -e DISPLAY=:1 --device /dev/snd -v /tmp/.X11-unix:/tmp/.X11-unix csicar/ubuntu-mate-desktop /usr/bin/mate-session

Window-Managers inside a container

As show here docker is not only useful for server applications, but can also be used for desktop applications.

Taking it a step further I wanted to run a window-manger from inside a docker container.

There are basically 2 steps to it:

1. Creating a virtual DISPLAY using a program like Xephyr
2. giving the container access to the DISPLAY

Creating a windowed X-Server

1. Installing Xephyr is pretty simple: Just do sudo pacman -S xorg-server-xephyr or sudo apt-get install xserver-xephyr
2. Now run Xephyr :1 -ac -br -screen 1024x768 -resizeable -reset -terminate to create a X-Server
   • :1 is the display-id; this will need to be passed to what ever wants to access the display
   • -ac disables access control restrictions
   • -br creates a window with a black background
   • -screen 1024x768 sets the default screen size
   • -resizeable makes the screen (for the guest) and the window (for the host) resizeable
   • -reset closes the host-window, when the guest exits the X-Server

Giving the container access to the DISPLAY

Just do: docker run -e DISPLAY=:1 -v /tmp/.X11-unix:/tmp/.X11-unix [container-id]

• -e DISPLAY=:1 will pass the value :1 as a environment variable DISPLAY through to the container
• -v /tmp/.X11-unix:/tmp/.X11-unix will pass the file through to the container`

The rest just like you are used to with docker.

Conclusion

Why?

because you can. And maybe because you can test new configurations of your WM (like i3) without worrying about breaking your main system.

What makes it better than virtualbox?

I get a lot beter performance when using a wm in a container instead of a vm.

Dockerfile

https://github.com/csicar/docker-wm