YaST2 Control Center is not running as root

Today when I wanted to set up a terminal server that brings a VNC desktop into a browser using guacamole I got this error when calling yast:

YaST2 Control Center is not running as root.
You can only see modules that do not require root privileges.

Ok, first thing I checked was that I am root indeed:

cloud-server-01:~ # who am i
root     pts/2        Jun 29 09:46 (krlh-4d034b34.pool.mediaways.net)
cloud-server-01:~ # id
uid=0(root) gid=0(root) groups=0(root)

Next thing was that I checked there is no mess around SUID bits or so. On my other computer where yast worked without problems I saw:

tweedleburg:~ # ll /sbin/yast
lrwxrwxrwx 1 root root 5 May 29 06:33 /sbin/yast -> yast2
tweedleburg:~ # ll /sbin/yast2
-rwxr-xr-x 1 root root 10273 May  2 12:42 /sbin/yast2

So no SUID bits or so. Ok, next thing to do was an strace:

strace -ffs 100 yast 2>file

This will execute yast, write a trace (strace), follow calls to sub-processes (ff), print a size of 100 characters per string (s 100) and redirect this to file. When looking at the file, funny enough, I remember the error message wrong, and I searched for "cannot". And there it was, the root-cause:

[pid 26593] clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f1f54664a10) = -1 ENOMEM (Cannot allocate memory)

After resizing my server from 512 MB to 1024 MB it worked.