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My df -h output:

root@haier-ubuntu:/# df -h
Filesystem                      Size  Used Avail Use% Mounted on
/dev/mapper/haier--ubuntu-root  457G  433G  691M 100% /
none                            4.0K     0  4.0K   0% /sys/fs/cgroup
udev                            1.9G  4.0K  1.9G   1% /dev
tmpfs                           385M  1.1M  384M   1% /run
none                            5.0M     0  5.0M   0% /run/lock
none                            1.9G  7.0M  1.9G   1% /run/shm
none                            100M  8.0K  100M   1% /run/user
overflow                        1.0M  4.0K 1020K   1% /tmp
/dev/sda1                       228M   88M  129M  41% /boot

See the line /dev/mapper/haier--ubuntu-root 457G 433G 691M 100% /, Used + Avail != Size and (Used / Size) * 100% != Use%. What is wrong?

Update:

I think this question is different from What is the difference between du -h and ls -lh?. The reason that du -h and ls -lh show different results is due to so called slack space. But my question is about reserved space.

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gzc
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  • Possible duplicate of [What is the difference between du -h and ls -lh?](http://serverfault.com/questions/290088/what-is-the-difference-between-du-h-and-ls-lh) – Jenny D Oct 13 '15 at 07:14
  • See for instance http://unix.stackexchange.com/questions/7950/reserved-space-for-root-on-a-filesystem-why – HBruijn Oct 13 '15 at 07:17
  • @HBruijn Thanks. This link tell me why there is reserved space in linux filesystem. – gzc Oct 13 '15 at 07:29

1 Answers1

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Most filesystems have some diskspace reserved for journaling, defragmentation, caching etc. Usually that is 5-10% of raw capacity.

Kondybas
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