[Techtalk] Different usage betweed df and du

Maria McKinley maria at shadlen.org
Wed Jul 13 15:49:00 EST 2005

Wow, that is a pretty significant difference.  I'm not sure this is very 
helpful, but maybe will give you some ideas.

I guess one of the first thing I would do is look at the subdirectories 
of /home using du and see if they make sense.  I'm assuming you are 
looking at du using something like:

du -h -d=1 /home

df is usually pretty straightforward and looks for free space, ie. if it 
says, so much used on such a disk, I'd trust it.  du works by going 
through directories and adding up file sizes, so I'm guessing it is 
missing something somewhere.  I'm not sure if du looks at dot files, so 
maybe there is a .trash somewhere that is really full?

Which number feels more accurate?  Do you think you should have about 
1GB used or 11GB?  That would be useful to know when looking for big 
files (whether they are likely to be hidden in a trash directory, for 

If you can't find anything, and you think your home should just be about 
1 GB, I would say that the disk has a bad spot on it (not sure what the 
correct terminology is), one that df thinks is being used, but du 
doesn't find files in.  Have you had any problems with this disk (other 
than problems caused by just being full)?  Do you have a backup, and how 
much room does that take?  Might want to do backup and run fsck.

good luck,

Sue Stones wrote:
> I received a message saying that /home is full.  (I deleted some stuff 
> so that I can get some work done.)
> When I run "df" it tells me that I have used 9.4 of my 11GB on /home 
> (before I deleted stuff it said I had used 11G)
> When I run "du" it tells me that /home has used 1.1GB.
> What it the likely cause of this difference?  How do I go about sorting 
> it out?
> Thanks to anyone who can help.
> sue
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