$ df -h
Filesystem                      Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-Backups  425G  377G   27G  94% /Backups
  • Size = 425G
  • Used = 377G
  • Available = 27G
  • Used + Available = 404G != 425G

Why is used+available different from total size? This is not happening in any other server.

I've tried remounting and rebooting the system.

du shows that the "Used" space in the /Backups directory from the df command is correct.


  • Slackware 13.37.0
  • Linux #1 SMP Sat Apr 9 14:01:14 CDT 2011 i686 Intel(R) Xeon(R) CPU E5530 @ 2.40GHz GenuineIntel GNU/Linux
  • HP DL360 G6
  • 1
    Hello BiFo. This is a programming Q&A site, not a general support forum. Please use a search engine, this type of question is asked (and answered) a lot.
    – Mat
    May 14, 2012 at 19:03
  • Possibly a portion of the filesystem capacity was automatically reserved for the superuser? Or you have some cleverly hidden something on there, or a broken filesystem. May 14, 2012 at 19:19
  • Try bind mounting your file system and see if there are any files hidden behind your mount points. May 14, 2012 at 22:35
  • 1
    See askubuntu.com/questions/79981/df-h-shows-incorrect-free-space (and tons of other similar discussions). May 15, 2012 at 7:01

1 Answer 1


This is most likely due to reserved space for the super-user on an ext2/ext3/ext4 filesystem, plus a small rounding error when converting blocks to gigabyte sizes. See this similar discussion.

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