"Cannot find file system superblock" error - how to recover?

[Sergey 'DoubleF' Zaharchenko]

On Wed, 4 Feb 2004 06:37:11 -0800 (PST)
"Scott I. Remick" <scott at sremick.net> probably wrote:

> --- Sergey 'DoubleF' Zaharchenko <doublef at tele-kom.ru> wrote:
> > And /dev/ad2s1e?
> 
> bash-2.05b# mount -r /dev/ad2s1e /data
> mount: /dev/ad2s1e on /data: incorrect super block
> bash-2.05b# fsck /dev/ad2s1e
> ** /dev/ad2s1e
> BAD SUPER BLOCK: MAGIC NUMBER WRONG
> 
> LOOK FOR ALTERNATE SUPERBLOCKS? [yn] y
> 
> USING ALTERNATE SUPERBLOCK AT 32
> ** Last Mounted on
> ** Phase 1 - Check Blocks and Sizes
> 416 BAD I=2
> 412 BAD I=3
> 424 BAD I=4
> 414 BAD I=4
> 417 BAD I=5
> INCORRECT BLOCK COUNT I=4257794 (8928 should be 9952)
> CORRECT? [yn]
> 
> Hmmm that looks more promising, although I'm not sure exactly what it's
> trying to warn me about, or how bad things are from that, so I'm going to
> leave it there for now. :)

This really looks weird. The incorrect block counts seem somewhat
suspicious.

Try using fsck -n (answer `no'), and recording what else comes up.

If you know what fsdb(8) is, it might be helpful (still with the -r
(read-only) option, and the -d option as well). I don't, but I'm
learning it intensively at the moment:).

> And if I remember correctly, even though fsck has used an alternate
> superblock to perform the repair process, it hasn't actually replaced the
> master superblock with the alternate one, so I'd still need to fix that
> manually somehow... correct?

Yes, by means of dd.

--
DoubleF
The only possible interpretation of any research whatever in the
`social sciences' is: some do, some don't.
		-- Ernest Rutherford
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