Bug#505137: grub-common: grub-probe returns fat for ext3 root fs

[Scott Ashcroft]

Felix Zielcke <fzielcke at z-51.de> wrote:

> 
> Am Sonntag, den 09.11.2008, 19:11 +0000 schrieb Scott Ashcroft:
> > Package: grub-common
> > Version: 1.96+20080724-11
>> Severity: important
> > 
> > 
> > grub-probe misdetects the root fs of one of my PCs (works fine on all others).
> > 
...
> > 
> > It looks like grub-probe runs the FAT checks before the EXT2 check and I just happen to hit a false positive.
> > 
> > Hopefully 512 bytes of the partition should be enough to debug this?
> > 
> > sa:/# hexdump -Cn 512 /dev/sda1
> > 00000000  eb 4a 90 00 65 6c 6c 20  38 2e 30 00 02 04 01 00  |.J..ell 8.0.....|
> > 00000010  02 00 02 00 00 f8 4f 00  3f 00 ff 00 3f 00 00 00  |......O.?...?...|
> > 00000020  86 39 01 00 80 00 29 09  08 d6 07 44 65 6c 6c 55  |.9....)....DellU|
> > 00000030  74 69 6c 69 74 79 00 41  54 31 36 20 20 20 00 00  |tility.AT16   ..|
>                                                                       ^^^
> Seems like you had a FAT filesystem there.
> If I make a 1 MB file and format it with mkfs.vfat then I have exactly
> at the same place FAT12
> If I then format the file with mkfs.ext2 the first 512 byte get zero'ed.
> So I wonder why you still have a FAT header in there.
> 
> Maybe we could check if bpb.fstype contains FAT12/FAT16/FAT32, then this
> would solve the problem for you but I don't know if it would introduce
> one for others.

I don't remember exactly how the box got installed. I'm pretty sure I just used an early Etch AMD64 install CD.
The FAT that's there looks like the original Dell recovery partition.
I've zeroed out the block and now everything works fine.
I'm happy for the bug to be closed as it's just my machine being weird.

Cheers,
Scott