Comment 26 for bug 262451

I got the same issue. It's first manifestation was when something has complained about a symlink in /usr during an update, but i wasn't paying attention and lost the logs. After reading and trying several things, i got to removing cups, and here's what i get:

~$ sudo dpkg --remove cups
(Reading database ... 143057 files and directories currently installed.)
Removing cups ...
 * Stopping Common Unix Printing System: cupsd [ OK ]
Processing triggers for ufw ...
ERROR: found symbolic link in path: /usr
dpkg: subprocess post-installation script returned error exit status 1

I do have a symlink in place of /usr. Is it forbidden for some reason? (I'm new to Linux)
The error appeared on first update after I replaced /usr with a symlink to a different partition.