My server seems to eat disks. Constantly at 99% and when it hits 100% php barfs and can’t store variables thence it won’t let people login.
Ubuntu helpdesk saves the day,
https://help.ubuntu.com/community/RecoverLostDiskSpace
with every damn possible CLI you can think of to hunt down and identify all the files that hog space. Saved me a hell of a lot of effort. Maybe you too.