Thanks for the quick reply!
No extra packages are installed, just PBS 3.x
However, PBS is installed as a vm on a Synology NAS. But that runs just fine.
(tempted to do a vm snapshot, but there are lots of GB's to "snapshot" and not much NAS...
short question:
in the PBS 3to4 upgrade wiki it is stated that minimum free space on "/" should be 10GB.
Can I upgrade with only 6GB free space or will I run into problems...?