Bad superblock
Hi
After a system crash, the superblock of /dev/hda4
(used for not so important data, hence no backup, sigh) is no longer readable.
An attempt to mount that device yields
/mnt # mount -t ext3 /dev/hda4 hda4
mount: wrong fs type, bad option, bad superblock on /dev/hda4,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
A simple fsck on that partition fails, since the first superblock seems to be
damaged:
/mnt# fsck /dev/hda4
fsck 1.37 (21-Mar-2005)
e2fsck 1.37 (21-Mar-2005)
fsck.ext3: Attempt to read block from filesystem resulted in short read while
trying to open /dev/hda4
Could this be a zero-length partition?
After that, I tried to use the first backup superblock and to mark the bad
blocks, verifying the position of that superblock with mke2fs -n,
and this resulted in
/mnt# e2fsck -ckv -b 32768 /dev/hda1
[...
Lots of bad blocks detected and file system errors corrected
...]
Error writing block 1 (Attempt to write block from filesystem resulted in short
write). Ignore error<y>? yes
Since the information could not be written, I was still not able to mount the
device. Also, the device can not be mounted giving the same superblock
information as above:
/mnt# mount -t ext3 -o sb=32768 /dev/hda4 hda4/
mount: wrong fs type, bad option, bad superblock on /dev/hda4,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
Dumping (part of) the data on the device with dd fails if one includes the
first block
/mnt# dd if=/dev/hda4 bs=4096 count=1
dd: reading `/dev/hda4': Input/output error
but succeedes if one ommits the first block (with skip=1).
Strangely enough, I had the same troubles with /dev/hda1 after the crash,
but there
/mnt# e2fsck -ckv -b 8193 /dev/hda1
solved the problem (the blocks are of 1k-size).
Is there a way to recover the data, since they turned out not to be so
unimportant after all? Any help would be appreciated, thanks in advance.
Greetings
Martin Schmid
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