[ltp] Disk damage?

Marius Gedminas linux-thinkpad@linux-thinkpad.org
Tue, 13 Jul 2004 22:06:55 +0300


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On Tue, Jul 13, 2004 at 08:43:31PM +0200, Ch. Veith wrote:
> I got a strange morning today...When I was booting my R40 I was=20
> wondering why my normal-user could not login to X-server, but root could!
> I thought that it might be a matter of diskspace and called df -h. It=20
> told me that that 0% were free - so I removed about 1GB to another=20
> machine. After that I called df again and still got 0% !!!

By default 5% (or 10%, I can't remember now) of free disk space is
reserved for the root user.  (The primary reason for this is that
ext2/ext3 does not suffer from fragmentation unless the partition fills
up, so keeping 10% always free is a good idea.  Also, the extra space
can be used in emergencies when some other user fills the disk.)

> After some testing around I removed another 2GB, and got the following:
>=20
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/hda2              37G   33G  1.7G  96% /

These 10% are not included in the "avail" column of df, so you now
actually have 1.7 + 1.5 GB =3D 3.2 GB physically free.

You can see the actual numbers with tune2fs -l /dev/hdaX:

  $ sudo tune2fs -l /dev/hda2
  tune2fs 1.35 (28-Feb-2004)
  Filesystem volume name:   <none>
  ...
  Inode count:              3784704
  Block count:              7567560
  Reserved block count:     378378
  Free blocks:              544080
  Free inodes:              3223487
  First block:              0
  Block size:               4096
  ...
  Reserved blocks uid:      0 (user root)
  Reserved blocks gid:      0 (group root)
  ...

On my 29 GB partition (7567560 * 4KB) 1.4 GB is reserved for user root
and group root.  2 GB is still free, but df -h only shows 648M free.

HTH,
Marius Gedminas
--=20
As far as we know, our computer has never had an undetected error.
                -- Weisert

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