If df -h reveals that one of your linux filesystems is full, you’ll be asking yourself whats filled it.
find /myfs -mtime +1 -type f -size +1000000 -exec ls -al {} \;
Replace /myfs with the the name of the filesystem thats filled according to df -h
Knock a zero off -size and repeat to drill down into the largest files
Add 1 to -mtime to go back 1, 2, 3 days etc to see the largest files written to in the last 1, 2, 3 days.
If you’re lucky enough to have a GUI and internet connectivity (highly unlikely on a linux server in the datacenter), install a tree mapper such as baobab (equivalent to sequoia view for Windows).