Display over SSH and inside a docker
====================================

Prerequisities:
  * /etc/ssh/sshd_config contains ''X11UseLocalhost no''
  * Assuming the use of ROS containers repo on git.cs.lth.se

Connect with -X or -Y (trusted) over SSH to the robot, using robotmind2 as an example here.

Run the first command to get your DISPLAY, it should be non-empty as otherwise the SSH connected with X11 forwarding failed.
<code bash>
$ echo $DISPLAY
robotmind2:12.0
</code>

In order for the container to connect it will also need a secret cookie that changes with each connection.

<code bash>
$ xauth list
robotmind2/unix:12  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
robotmind2/unix:11  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
robotmind2/unix:10  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
robotmind2:10  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
robotmind2:11  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
robotmind2:12  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
</code>

The cookie is different in the real world, but in hex. Copy the relevant one based on your $DISPLAY

Then go inside your container:
<code bash>
$ export DISPLAY=robotmind2:12.0
$ xauth add robotmind2:12  MIT-MAGIC-COOKIE-1  0123456789abcdef0123456789abcdef
</code>

Change names as needed, xauth add should have the matching cookie for your $DISPLAY.

Now X11 forwarding should work over ssh inside a docker container.