Recovering a Lost Partition Using Gpart

December 22, 2009 Category: Uncategorized

Even today people do not understand how important it is for the safety of your data to make backups. I was asked to perform some data recovery on a hard drive of an old computer, which still contained important documents and photo's.

The first thing I did was to make a disk image with ddrescue. I always work with the image and not with the original drive, to prevent any risk of accidentally messing things up for good.

Example:

ddrescue -r 2 -v if=/dev/sdf of=/storage/image/diskofperson.dd bs=1M

Next, I tried using gparted on this file but got this error:

Welcome to GNU Parted! Type 'help' to view a list of commands.

(parted) p

Error: /storage/image/diskofperson.dd: unrecognised disk label

(parted) quit

Also fdisk -l didn't work:

Disk /storage/image/diskofperson.dd doesn't contain a valid partition table

It seemed that the partition table was gone. I used the utility testdisk to recover this partition, to no avail. Why this tool didn't work is beyond me.

I found a very old utility called 'gpart' that just searches a disk for existing partitions. I just want to know the starting offset of the relevant partition.

So I ran:

gpart -g /storage/image/diskofperson.dd

And I got nothing useful, although a partition was found:

Begin scan...

Possible partition(DOS FAT), size(57255mb), offset(0mb)

End scan.

So I ran the command again with more verbosity:

gpart -g /storage/image/diskofperson.dd

...

Begin scan...

Possible partition(DOS FAT), size(57255mb), offset(0mb)

type: 011(0x0B)(DOS or Windows 95 with 32 bit FAT)

size: 57255mb #s(117258372) s(63-117258434)

chs: (1023/255/0)-(1023/255/0)d (0/0/0)-(0/0/0)r

hex: 00 FF C0 FF 0B FF C0 FF 3F 00 00 00 84 38 FD 06

End scan.

...

This time I got something useful. The s(63-117258434) part shows the starting sector, which is 63. A sector is 512 bytes, so the exact starting offset of the partition is 32256.

So to mount this partition, just issue:

mount -o loop,ro,offset=32256 /storage/image/diskofperson.dd /mnt/recovery

And voilá, access to the filesystem has been obtained.

/storage/image/jdiskofperson.dd on /mnt/recovery type vfat (ro,loop=/dev/loop0,offset=32256)

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