Subject: Re: du & df
To: Lars Heidieker <firstname.lastname@example.org>
From: Robert Elz <kre@munnari.OZ.AU>
Date: 11/13/2001 00:04:57
Date: Mon, 12 Nov 2001 11:00:42 +0100
From: Lars Heidieker <email@example.com>
| Wouln't that be the other way around df showing less in use then du.
No. That should be impossible (race conditions excepted).
| I think a bunch of sparse files will cause this.
An open file (or files) that have been unlinked is the likely cause.
It also used to be the case (perhaps still is?) that if the filesys was
mounted with softdeps, and files had been deleted, it would take a while
for df to catch up (the space isn't actually released to the filesystem
immediately). On the other hand, du only ever shows the files that are
currently in directories.
A third (but very unlikely in this case I suspect) cause can be if some
other filesystem is mounted on top of the one under consideration, and it
is almost empty (so du finds little) but there's actually lots of files
that are now hidden under the mount point (the space is still in use on
the filesystem, but nothing can get at it - du included).