Repair FAT hard drive superblock

conormacaoidh · 01-11-2012, 03:47 PM

Hi,

I'm attempting to fix a friend's hard drive for them. I'm pretty sure its formatted with FAT, but can't be certain. It's a 2.5" drive, i stripped the case and used a hard drive enclosure to access it.

I can't mount the drive, but "/dev/sdb" does appear when I plug it in. When trying to mount the drive i get this error:

Code:

[root@conor ~]# mount /dev/sdb /mnt/temp
mount: /dev/sdb: can't read superblock

fdisk -l doesn't show the disk, gparted doesn't show the disk.

I've tried fsck as well:

Code:

[root@conor ~]# fsck.vfat /dev/sdb
dosfsck 3.0.12, 29 Oct 2011, FAT32, LFN
Got 0 bytes instead of 512 at 0

I've also tried using testdisk to examine the drive, but it doesn't show up on the list of devices within fdisk.

I'm really at a loss as to what to do next, any advice would be helpful

thanks

Doc CPU · 01-11-2012, 04:03 PM

Hi there,

Quote:

Originally Posted by conormacaoidh

Code:

[root@conor ~]# mount /dev/sdb /mnt/temp
mount: /dev/sdb: can't read superblock

have you tried to force -t vfat? Probably you have, to no avail.

Quote:

Originally Posted by conormacaoidh

fdisk -l doesn't show the disk, gparted doesn't show the disk.

I've tried fsck as well:

Code:

[root@conor ~]# fsck.vfat /dev/sdb
dosfsck 3.0.12, 29 Oct 2011, FAT32, LFN
Got 0 bytes instead of 512 at 0

I've also tried using testdisk to examine the drive, but it doesn't show up on the list of devices within fdisk.

That's really weird. Summing all up, my concern is that the drive may be physically corrupted. Things like these happen when the drive's controller isn't able to even access the disk itself. Then it would announce itself as an IDE or SATA controller to the host system, but with no storage media. Had exactly that with a Fujitsu HDD a few years ago: It reported itself correctly to the BIOS, with type and model number, but any attempt to read a sector would only produce a block of 0-bytes.
Does your friend have precious data stored on that disk? If not, I'd declare the unit junk; if yes, consider spending a few 100$ for a professional data rescue expert.

[X] Doc CPU

mmrtnt · 01-11-2012, 05:21 PM

I seem to remember something about alternative superblocks.

I looked this up real quick.

Good luck!

business_kid · 01-13-2012, 02:58 PM

Quote:

[root@conor ~]# mount /dev/sdb /mnt/temp
mount: /dev/sdb: can't read superblock

It's trying ext. You want MBR, not superblock. and you want the partition

mount -t vfat or -t ntfs-3g /dev/sdb1

Presuming that doesn't work

If fdisk -l doesn't show it that looks grim. Try
hdparm -i /dev/sdb
hdparm -I /dev/sdb
smatrctl [clevber optione] /dev/sdb # man smartctl with coffee required

The first reads what the kernel picked up, the second asks the disk personally. Rhe third is a health check.

The best for that sort of thing is testdisk, imho. also try

dd if=/dev/sdb of=mbr bs=512 count=1. That's the mbr.

jefro · 01-13-2012, 05:31 PM

Mount it raw and look at the first few blocks with a hex editor.

Doc CPU · 01-14-2012, 04:10 AM

Hi there,

Quote:

Originally Posted by business_kid

and you want the partition

mount -t vfat or -t ntfs-3g /dev/sdb1

I guess using sdb1 (the partition) instead of sdb (the entire drive) is the key here. I completely missed that in my first post too.
By the way, I would preferrably leave the -t parameter out and let the OS auto-detect the file system. Works well most of the time.

[X] Doc CPU