[CentOS] very large difference between df and du (10 GB, hard to believe)

Robert Heller heller at deepsoft.com
Mon Feb 1 15:58:37 UTC 2010


At Mon, 1 Feb 2010 08:36:29 -0700 CentOS mailing list <centos at centos.org> wrote:

> 
> On Mon, Feb 1, 2010 at 8:29 AM, Robert Grasso
> <robert.grasso+nv at cedrat.com> wrote:
> > Hello,
> >
> > I have a small server running a tool (RT : perl + mysql + apache) for our support team. I stripped down everything else. The OS is
> > CentOS 4.8. I noticed a difference between df and du which is hard to believe :
> >
> > according to df, I am using 29 GB
> >
> >
> > [root at cedrat-rt ~]$ df -h
> > Filesystem            Size  Used Avail Use% Mounted on
> > /dev/sda1              33G   29G  2.8G  92% /
> > none                  506M     0  506M   0% /dev/shm
> >
> > (there are no other partitions - ok, I could have partitioned it a bit more)
> >
> > but according to
> >
> > du -kshxc /*

This might be wrong -- are there any files starting with '.' under /? 
What does 'du -kshxc /' display?

Are df and du *still* off after the reboot?

When you boot with the live CD is df and du *still* off?  With the live
CD, what does a 'du -sh /mnt/<mumble>/{sys,proc,dev}' show (where
<mumble> is the mount point for you hard drive partition)?  In other
words, do you have stuff under the various tmpfs/kernel mount points?

> >
> > my largest directory is /var (because of mysql) and the grand total is
> >
> > 19 GB
> >
> > I have a 10 GB difference between both outputs.
> >
> > I verified with
> >
> > tune2fs -l /dev/sda1
> > (...)
> > Block count:              8703205
> > Reserved block count:     435160
> >
> > that is, the ordinary 5%
> >
> > the journal size :
> >
> > debugfs -R "stat <8>" /dev/sda1
> >
> > yields
> >
> > Size: 33554432 with a block size of 4096, this gives 128 MB
> >
> > I rebooted on the CentOS v4.8 CD #1, started "linux rescue" :
> >
> > mounting /dev/sda1, I get the same 29 GB used
> >
> > e2fsck reports a clean filesystem
> >
> > e2fsck -f does not reports further errors.
> >
> > Does anybody have a suggestion ?
> >
> > Best regards
> > ---
> > Robert GRASSO - System engineer
> >
> >
> > _______________________________________________
> > CentOS mailing list
> > CentOS at centos.org
> > http://lists.centos.org/mailman/listinfo/centos
> >
> 
> This is typical.  There were probably files deleted from the file
> system that are still in use by a process.  Restarting the process
> will release the files and df and du will jive.

The OP rebooted with a live CD, which should have dealt with any
lingering processes :-)

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>                                      

-- 
Robert Heller             -- 978-544-6933
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