minus disk usage

[Alheid, Gregory]

> From: Uematsu Takeshi <takeshi.uematsu at gmail.com>
> To: ext3-users at redhat.com
> Subject: minus disk usage
>
> Hi,This is Takeshi Uematsu.
>
> I have a trouble on the ext3 filesystem.
> The df command indicates minus disk usage.
> Dose anyone know why this happned ?
> Any ideas be appreciated.
>
> # df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda2              97G  -26G  118G   -  /
> /dev/sda1              99M   15M   80M  16% /boot
> tmpfs                 2.0G     0  2.0G   0% /dev/shm
> /dev/sda3             803G  3.9G  758G   1% /home
>
> fdisk /dev/sda
>
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1   *           1          13      104391   83  Linux
> /dev/sda2              14       13067   104856255   83  Linux
> /dev/sda3           13068      121193   868522095   83  Linux
> /dev/sda4          121194      121454     2096482+  82  Linux swap / Solaris

You should really do a fsck of the "/" FS. You should have a backup 
before doing a fsck because if there are major errors, running a 
fsck can make a FS unusable.

A couple of other things you can try before doing a fsck are:

Use dumpe2fs and see if there are any issues;

  dumpe2fs /dev/sda2


Use find cmd to list any "unusually" large files, adjust the 
value +100000 as needed;

    find / -mount -size +100000 -exec ls -l {} \;

Check the sizes of the directories and files within, here is a 
variation of a script I use to do this to list the 10 largest 
directories of the "/" FS;

  for d in $( ls -1 / ) ; do

    if [[ "x$d" = "xboot" || "x$d" = "xhome" ]] ; then
     :
    else
      ls -d /$d
      du -sk /$d
    fi

  done | sort -n | tail
  
You can then check each of the listed directories with the following;

  du -sk /usr/* | sort -n | tail

and do this on the directories listed until you find the issue.

Lastly re-boot the system with a CD installed it the system with, or 
later, enter "linux rescue" and run fsck on the root FS. If there 
are any errors, answering yes will try to correct the FS errors. 
  
Greg