[SunHELP] Currupt superblock and alternates

[velociraptor]

On 9/28/06, Reed Stoner <kaltekar at gmail.com> wrote:
> Having a bit of trouble with a scsi drive that has a bad superblock in
> Solaris 9.  I've tried running fsck with an alternate super block and
> it is still comming back with the error
>
> BAD SUPER BLOCK: MAGIC NUMBER WRONG
> USE AN ALTERNATIVE SUPER BLOCK TO SUPPLY NEEDED INFORMATION
> e.g. fsck [-F ufs] -0b=# [special...] where # is the alternative super block
>
> Any alternative super block I try using newfs -N returns the same
> error.  I'm trying to retreive the data on the drive because it
> doesn't have any back up. (someone forgot to add this server to the
> backup scheme) Any help would be handy.

"Magic number wrong" indicates the disk label or the filesystem type
in the partition info is corrupt.

You might want to have a look at this archive summary in the
Sunmanagers mail archives:
<http://www.sunmanagers.org/pipermail/summaries/2002-November/002695.html>

As a *last* resort if you have another disk of the exact same geometry
that you know has been partitioned *exactly* the same way, you could
try using the prtvtoc->hardfmt[0] command to put a new label on the
disk.

I say "last resort" because if you are guessing as to the
partitioning, doing a prtvtoc->hardfmt will totally trash any existing
good partial partition info on the disk with the bad label.  Needless
to say, I'd try other methods of recovery first, up to, and including
a dd of the disk if you don't have known good backups.

=Nadine=

[0]prtvtoc /dev/rdsk/cXtYd0s2 | fmthard -s - /dev/rdsk/cAtB}d0s2
                            ^^                                             ^^
                            disk with good label
disk with bad label