I was running out of space on a server the other day and was wondering what directory was full and what files I could clean up. There is a simple command that is helpful to identify usage by directory. This works from within any directory so you can walk the path from / down through your largest directories and look for files to clean up.

[root@localhost]# du -hc --max-depth=1
4.0K ./misc
4.0K ./srv
576K ./root
29M ./sbin
16K ./tmp
2.0G ./usr
731M ./proc
12M ./boot
0 ./sys
379M ./appserver
28M ./opt
447M ./var
85M ./lib
8.0M ./etc
11M ./home
0 ./selinux
6.3M ./bin
16K ./lost+found
40K ./dev
24K ./mnt
3.7G .
3.7G total