Disk usage on a specific filesystem

Question

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
nfshome.XXX.net:/home/userA
                      5.3T  1.6T  3.5T  32% /home/userA
nfshome.XXX.net:/home/userB
                      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/
  

Solution 1

Use the -x (single file system) option:

du -cshx /

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

Solution 2

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 /

Comments

[Amelio Vazquez-Reina]

Thanks Stephen. Not sure this works the way I understand it does (see this followup)

[user855443]

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"?

[nealmcb]

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.

[koppor]

To find directories containing a large size, I would recommend adding --max-depth=1: du --human-readable --one-file-system --max-depth=1