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Re: df discrepencies

On Mon, 2006-05-01 at 10:08 -0400, charlie derr wrote:
> On one of the machines that I oversee there is an issue with the df
> output that I don't understand.
> here's a part of the output from df -h
> /dev/sda1             440G  420G     0 100% /backup
> if i don't use the -h it looks like this:
> /dev/sda1            461293804 440335112         0 100% /backup
> It appears that there really are 20Gigs free, but that column shows 0
> -- can i reliably ignore that column and use subtraction with the 
> previous two to compute the true free space?

        dumpe2fs -h /dev/sda1

will show you exactly what is going on. On filesystems I have I want to
use the entire filesystem, I set the reserve to 16384 blocks (making the
reserved amount 64MB on ext3)

You can do this with:

        tune2fs -r 16384 /dev/sda1

I also typically disable max-mount-counts, causing fsck to run only when
unmounted uncleanly or after so much time.

So, really the command I use to for maximizing the amont of disk space
for general user use and so on is as follows:

        tune2fs -r 16384 -c 0 -e continue -i 3456000 /dev/sda1

BTW, 3456000 is 40 days.

> If I clear up enough more diskspace the 4th column will eventually
> show more than 0, but it won't be equivalent to the difference of the
> 2nd 
> and 3rd.   My recollection is that rebooting will fix this problem
> (for a while), but I'd prefer not to have to reboot every couple
> weeks.

What are you talking about? That only clears /tmp files from the /
or /tmp directories.

> This machine is running sarge and that partition is ext3 over a RAID5
> array.  I do slip up on occasion and allow this partition to 
> completely fill up (not sure if that might be relevant) so that the
> rsync processes that are writing to it fail (because of no more 
> remaining disk space).

Please make sure you wan to do this before you go any further. I have
had years and years of working with *NIX and can basically take risks
that other could not, as I understand *WHAT* I am trying to accomplish.
Not that I am saying you don't, just make sure you understand the
consequences, before you do.
greg, greg@gregfolkert.net

The technology that is 
Stronger, Better, Faster: Linux

Use Debian GNU/Linux, its a bazaar thing

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