Find the giants
You have many files and directories on your Linux or Unix server. Normally they sit quietly, waiting for you to look at them. Sometimes they grow enormous while you are not watching! Now you are getting paged because your disk is almost full. What do you do?
What are you du-ing?
On a Linux system, you use the du
command at the “root” of your file system to find and summarize each top-level directory size.
For example, here we are using -x
to stay on the /
(root) filesystem, and sorting by size:
# du -x --max-depth=1 / | sort -n 4 /media 4 /srv 12 /mnt 16 /lost+found 24 /tmp 6932 /bin 7592 /sbin 10652 /etc 20792 /home 22928 /boot.bak 75244 /opt 252124 /lib 715504 /usr 1040008 /root 2059816 /var 4211656 /

Source: Wikipedia
/var
is the biggest directory of /
. If we descend into /var
and again run du
, we eventually find the big files:
# ls -ls /var/cache/ | sort 102400 -rw-r--r-- 1 root root 104857600 May 22 18:07 its 103424 -rw-r--r-- 1 root root 105906176 May 22 18:08 a 104448 -rw-r--r-- 1 root root 106954752 May 22 18:08 giant 105472 -rw-r--r-- 1 root root 108003328 May 22 18:08 lion 106496 -rw-r--r-- 1 root root 109051904 May 22 18:08 get 107520 -rw-r--r-- 1 root root 110100480 May 22 18:08 in 108544 -rw-r--r-- 1 root root 111149056 May 22 18:08 the 109568 -rw-r--r-- 1 root root 112197632 May 22 18:08 car 4 drwx------ 2 root root 4096 Feb 21 10:50 ldconfig 4 drwxr-xr-x 26 man man 4096 May 22 06:25 man 4 drwxr-xr-x 2 root root 4096 Feb 21 10:51 debconf 4 drwxr-xr-x 2 root root 4096 Nov 13 2018 unbound 4 drwxr-xr-x 3 root root 4096 May 22 15:36 apt total 847892
Find it faster
There is a utility that both speeds this up, and keeps things sorted and organized for you: ncdu. Install it using apt/yum install ncdu
. Then launch it using ncdu -x /
.

ncdu
has already ordered the files and directories. It has even preselected the largest directory. Now we hit the “right-arrow” key, and descend all the way to /var/cache
:

From here, you can use the d
key to delete files (be careful!), the arrow keys to navigate, or q
to exit.