Another possible way of getting backup superblock info is with
# mke2fs -n /dev/<your device>
And then use this with
#e2fsck -b <backup block> /dev/<your device>
mke2fs with the -n switch, runs as though it would create a new filesystem
without actually writing anything to disk. So it tells you where it would
put the backup superblocks if it were to run in full filesystem creation
mode. This means that if you use different parameters from the ones used in
actually creating the file system to begin with, you may get the wrong
backup superblock info. Nothing should break by doing this anyway.
> -----Original Message-----
> From: centos-bounces@xxxxxxxxxx [mailto:centos-bounces@xxxxxxxxxx] On
> Behalf Of Jason T. Slack-Moehrle
> Sent: 31 January 2012 02:38
> To: CentOS mailing list
> Subject: Re: One of my servers wont boot today
>
> > > > It says:
> > > >
> > > > /dev/VolGroup00/. The superblock could not be read or does not
> describe a correct ext2 filesystem. If the device is valid and it
> really contains an ext2 filesystem (and not swap or ufs or something
> else), then the superblock is corrupt, and you might try running e2fsck
> with an alternate superblock: e2fsck -b 8193 <device>
> > > >
> > > > So I tried e2fsck -b 8193 /dev/VolGroup00
> > > >
> > > > and it seems I get the same error coming up over and over
> > > >
> > > > I tried:
> > > >
> > > > fsck -y b=8193 /dev/VolGroup00 as well
> > > >
> > > > Any thoughts?
> > >
> > > You need to fsck each logical volume, not the whole volume group,
> e.g.
> > >
> > > e2fsck -b 8193 /dev/VolGroup00/LogVol01
> > sure, I thought of that too.
> >
> > under /dev/VolGroup00 is LogVol00, LogVol01, LogVol02.
> >
> > I do e2fsck -b 8193 /dev/VolGroup00/LogVol00 and I get the same super
> block error above.
> >
> > Same with LogVol01 and 02.
> Forgot:
>
> e2fsck: Bad magic number in super-block while trying to open LogVol00
>
> The superblock could not be read or does not describe a correct ext2
> filesystem. If the device is valid and it really contains an ext2
> filesystem (and not swap or ufs or something else), then the superblock
> is corrupt, and you might try running e2fsck with an alternate
> superblock:
> e2fsck -b 8193 <device>
>
>
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