Re: read-only drive with reiserfs partiton not mountable

[Carl-Daniel Hailfinger <c-d.hailfinger.kernel.2003@gmx.net>]

Carl-Daniel Hailfinger wrote:
> [Sorry, I hit send a bit too early]
> Carl-Daniel Hailfinger wrote:
> 
>>Joel Ebel wrote:
>>
>>
>>>Ok.  I've got an unusual problem.  My hard drive decided yesterday to
>>> turn read-only.  I can't write anything to it.  The data seems to be
>>>all there and readable, but any write to the drive fails.  I have 
>>>partitions of NTFS, FAT32, ext3, and reiserfs.  I'm able to mount all
>>> the other partitions and copy files off of them, but the reiserfs 
>>>partition refuses to mount saying wrong fs type, bad superblock,
>>>etc... Is there a reason that a reiserfs partition on a read-only
>>>drive wouldn't mount?  I'd sure like to get what data I can off of
>>>it.  Any ideas?
>>
>>
>>Use UML (user-mode Linux) and arrange for writable backing store on 
>>another fs.
> 
> 
> To be more clear, the block device with reiserfs is the base for a COW
> (copy on write) device which can be used under UML. For the writes, you
> need to provide a file on a writable fs which will store the differences.
> ReiserFS inside the UML will not notice the fact that you tricked it.

If /dev/hdb8 is your read-only filesystem, try this:

./linux ubd1=reiser_cow,/dev/hdb8

and once you have booted the linux instance,

mount /dev/ubd1 /mnt

Another option is to copy the partition to a file on a writable fs and
loop mount it from there.

dd if=/dev/hdb8 of=/tmp/fsbackup
mount -o loop /tmp/fsbackup /mnt

The last option for coping with a readonly disk is to copy it over
completely with dd. Assuming /dev/hdb is your damaged disk and /dev/hdc is
your new shiny IDENTICAL model, you can also

dd if=/dev/hdb of=/dev/hdc

Note: If you are someone longing for SPEED, you can add bs=1M to the dd
commands. That should help quite a bit.


HTH,
Carl-Daniel
-- 
http://www.hailfinger.org/