I fixed a permissin problem for nagios like discribed here.
The command was:
sudo dpkg-statoverride --update --add nagios www-data 2710 /var/lib/nagios3/rw
sudo dpkg-statoverride --update --add nagios nagios 751 /var/lib/nagios3
Okay its obvious that it is some sort of permission altering. But where does it take place? Where is it stored? Is it just a chmod modification?