Sehr geehrter Dr. Nikolaus Klepp,

> Ok. To run programs as root on X11 you need to transfer X credentials
> to root. This can be done by hand (eek!) or just use "sux". 

Probably also the reason sux is dead upstream and sux was pretty much
a Debian issue.

To /etc/pam.d/su add:
---8<---
# Forward xauth keys between users if invoker is root or UID 1000 or
higher 
session  optional  pam_xauth.so systemuser=999
--->8---  

A 6 year old patch, that still works.

Regards, Peter.