[SWLUG] Kernel panic - not syncing: VFS: unable to mount root fs on unknown-block(3, 8)

[Neil Greenwood]

On 04/04/06, Julian Hall <lists at kaotic.co.uk> wrote:
>
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> Neil Greenwood wrote:
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> > Julian,
> >
> > The way I used the live CD is as follows (since I didn't make it
> > clear earlier):
> >
> > 1. Boot the live CD
> > 2. Mount the broken root partition into any directory of the running
> > live CD: in my case, I mounted it in /mnt
>
> Problem straight away here.  Knoppix mounted all the partitions except
> the broken one.  Ubuntu (5.10 Live) didn't mount any so I had to
> create the root user login just to be able to do it manually.  I
> mounted hda1 using the commands:
>
> mkdir /mnt/test$a
> mount /dev/hda1 /mnt/test1
>
> That worked.  However trying to mount /dev/hda2 as /mnt/test2
> complains about not knowing the fstype.  Why would this one be
> complaining when the first didn't?  Incidentally hda1 is the Windows
> C: drive.
>
>
Julian,

If you're trying to fix the Linux installation, I wouldn't mount the Windows
partitions, just in case :-)

Is /dev/hda2 the root partition that's broken? Can you remember what file
system is on there?

You might be able to find out using fdisk with the -l (lower-case L) option,
on the whole disk (not the hda2 partition), like so:
  fdisk -l /dev/hda
This should list all the partitions on the disc, together with the partition
table's idea of what file system is on there. This isn't 100% reliable,
since both ext2 and ext3 have the same identifier (0x82, i.e. 130 in
base-10, but you enter it in hex), and I had a case recently where I managed
to format a FAT32 (0xB) partition with ext2...

When you know what partition type it is, use the -t option on the mount
command, e.g.:
  mount /dev/hda2 -t ext2 /mnt/test2
Obviously, this is just an example and you need to change the values
appropriately. cat /proc/filesystems will tell you what fstypes the current
kernel knows about - this list can change when you load extra filesystem
modules.


If you can't find out what file system type it is, you could try a couple of
likely fstype values after the -t option, and use "-o ro" to mount
read-only. *WARNING* This may corrupt the filesystem, but I don't think it's
very likely - I haven't tested it though. But at this point, your partition
might be hosed anyway...


You do have a backup, don't you ;-)

Cheers,
Neil.
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