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Re: Need Help restoring a filesystem on an external drive WD 'My Book'




Hi,

arne wrote:
> and I doubt if I understand what is a 'sparse' superblock

It's not a bad sign, as it seems:

  http://www.nongnu.org/ext2-doc/ext2.html#SUPERBLOCK
  "The first version of ext2 (revision 0) stores a copy at the start of
   every block group, along with backups of the group descriptor block(s).
   Because this can consume a considerable amount of space for large
   filesystems, later revisions can optionally reduce the number of backup
   copies by only putting backups in specific groups (this is the sparse
   superblock feature)."


> Command line: TestDisk /log /dev/sdb
> ...
> 1 P partition_map                  1         63         63

Looks like it recognized a GUID partition table (GPT).

> 3 P HFS                       262208 1953525151 1953262944

This would be the ext filesystem's partition.
The following superuser command establishes a read-only loop device which
begins at the given block:

  losetup -o $(expr 262208 '*' 512) -r -f /dev/sdb

(Contrary to the man page, losetup -f does not tell me the used device path.
 I have to run
   losetup -l | fgrep /dev/sdb
 to learn that it's /dev/loop0.)


>     Linux                     262208 1953525151 1953262944
>     ext2 blocksize=4096 Large file Sparse superblock, 1000 GB / 931 GiB
> recover_EXT2: "e2fsck -b 32768 -B 4096 device" may be needed

This is probably the normal superblock in that partition.
But running e2fsck might cause the end of the remaining data in the
filesystem.

I'd try to mount the loop device and hope to recover some files.
When this is queezed out, then maybe a run of e2fsck might recover more
valid files ... or ruin the filesystem.


Have a nice day :)

Thomas