I need to find out what's contributing to the disk usage on a specific filesystem (/dev/sda2):

$ df -h /
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              96G   82G  9.9G  90% /

I can't just do du -csh / because I have many other filesystems mounted underneath /, some of which are huge and slow:

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              96G   82G  9.9G  90% /
/dev/sdb1             5.2T  3.7T  1.3T  76% /disk3
/dev/sda1              99M   18M   76M  20% /boot
tmpfs                  16G  4.0K   16G   1% /dev/shm
                      5.3T  1.6T  3.5T  32% /home/userA
                      5.3T  1.6T  3.5T  32% /home/userB

How can I retrieve disk usage only on /dev/sda2?

None of these work:

  • Attempt 1:

    $ du -csh /dev/sda2
    0       /dev/sda2
    0       total
  • Attempt 2:

    $ cd /dev/sda2/
    cd: not a directory: /dev/sda2/
  • Maybe I am missing something, but why doesn't the Used column give you what you are looking for?
    – StrongBad
    Apr 11, 2017 at 13:44

2 Answers 2


Use the -x (single file system) option:

du -cshx /

This instructs du to only consider directories of / which are on the same file system.

  • Thanks Stephen. Not sure this works the way I understand it does (see this followup) Apr 11, 2017 at 13:45
  • Note that the magic here is the -x option. The other options here, mirroring the OP approach, report in human-readable numbers, and summarize the results, including a grand total. So for example, du -x / would give a full description of all files on the root file system.
    – nealmcb
    Jul 31, 2021 at 17:03

There are two options to solving your problem:

Using the option --exclude which makes du ignore the given path.

du --human-readable --exclude=/home

Using the option --one-file-system would tell du to not go into a different file system.

du --human-readable --one-file-system /
  • I have home on a different partition but when I use `du -hd1x ` the home directory is included. I use debian stretch. What do I misunderstand in "one file system"?
    – user855443
    Nov 26, 2018 at 22:56
  • To find directories containing a large size, I would recommend adding --max-depth=1: du --human-readable --one-file-system --max-depth=1
    – koppor
    Sep 24, 2021 at 7:50

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