Re: xfs_repair force_geometry

[Eric Sandeen <sandeen@sandeen.net>]

On 5/13/13 7:24 AM, Benedikt Schmidt wrote:
> Hi, currently I'm looking for the correct usage of the force_geometry
> option of xfs_repair. I wasn't able to find more documentation on
> this option beside that it exists. Could please somebody explain it
> to me?
> 
> For a more detailed description of my problem: I've got here a hard
> disk which is dying at the moment, so I copied all the content with
> dd_rescue to a new and bigger one. To use xfs_copy wasn't possible as
> the filesystem was already corrupted. So now I've got nearly
> everything on the second hard disk (dd_rescue could'nt copy something
> around 6 or 7 MB), but I can not mount the filesystem or even run
> xfs_repair on it, as it fails to find a superblock. I think the
> problem lies in the fact that the new disk has a different geometry
> than the previous one.

the geometry in "force_geometry" refers to the filesystem geometry,
not the CHS geometry of your disk.

It's only needed if the fs has only 2 allocation groups and they don't
match, or if the fs has only a single allocation group (and therefore
has nothing to test against).

So I don't think that's the option you need.

I don't know what you copied the fs to, but perhaps you copied the
entire disk, not the partition.  

How did you invoke dd_rescue?

If you dd_rescued to a file, what does:

# file <file you dd'd to>

say?

Or, if you dd_rescued to a device, what does

# file -s <dev you dd'd to>

say?

-Eric

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