Recovering XFS Partition of Type FAT16

[Eric Sandeen]

On 7/7/11 2:57 PM, Volkan YAZICI wrote:
> On Thu, Jul 7, 2011 at 6:53 PM, Eric Sandeen <sandeen at sandeen.net> wrote:
>> It sounds like something changed your partition table as well as your
>> filesystem.  Putting the partition table back in place first probably
>> would have been the better first step, in retrospect.
>>
>> I can't tell for sure, though, what you've done (did you reparition?
>> mkfs?  with which tools?  what was the xfs_repair output?) so I'm not
>> sure what to tell you at this point.
> 
> I was struggling to boot an ISO image from a USB disk, hence I suspect
> that I had probably set the type of the host machine partition
> (/dev/sda1) to FAT16 with fdisk, instead of USB disk partition

well, almost nothing cares about the partition type, really...
not kernel, anyway, and not mount ...

> (/dev/sdb1). Then in the next boot, Linux doesn't come up and
> complained about XFS issues. Hence I rebooted the machine and repaired
> the fs with xfs_repair. This time partition is mounted properly but a
> significant portion of the disk content is missing. Then in the fdisk
> -l output I realized that /dev/sda1 is set to FAT16. (Isn't it strange
> that I can xfs_repair and mount a partition of type FAT16?) Later I

no, not really, (almost) nothing cares about those couple bytes in the 
partition table...

> set the type of /dev/sda1 to Linux, but nothing changed. I called
> xfs_repair again and tried mounting again, no luck: same fs size
> (20GB), same missing contents.
> 
> For the xfs_repair output... Honestly, I don't remember and I don't
> think I can reproduce the situation.

And I'm afraid I can't really imagine how you got here; apparently
your partition got shrunk, at least - and maybe mkfs'd as FAT?
And I don't think repair will cope well with a truncated block device...
perhaps your handy partitioning tool helpfully mkfs'd for you a few
times, as well...?

-Eric

> 
> Best.
>