Disk usage per user in Linux / Unix Print

Here is a simple and quick solution that I believe meets your requirement.

I assume that all your users have accounts in the /home directory. All you need to do is to change directory to the /home directory, and then do a du at a depth of 1.

cd /home
sudo du -d 1 -h

Your output will look something like this:

root@sisrv:/home# sudo du -d 1 -h
395M    ./Backups
2.1G    ./john
168K    ./debian
1.1G    ./sam

Or for finding the problem users (directories too),

du -xk | sort -n | tail -25