Quota

Set up

As root:

apt-get install quota quotatool

update /etc/fstab:

/dev/sdb1 /home ext4 usrquota,usrjquota=quota.user,jqfmt=vfsv0 0 0

Then run these commands:

touch /home/quota.user
chmod 600 /home/quota.user
mount -o remount /home
quotacheck -avum
quotaon -avu 

Manage

To see usage and quotas for all users:

repquota -a

To set a soft limit of 30GB and a hard limit of 32GB for barney:

setquota barney 31457280 33554432 0 0 /home

To copy barney's limit to charlie and darwin:

edquota -p barney charlie darwin

To turn quotas off and on:

quotaon
quotaoff

References

http://www.ubuntugeek.com/how-to-setup-disk-quotas-in-ubuntu.html

notes on journaled quotas: http://ubuntuforums.org/showthread.php?t=1014051&page=2