Can't Read Superblock

[JediMasterOdd]

Hi Lads and Lasses,

I've been toying with Ubuntu on and off for a while now but still know very little about what I'm doing, I can use Google to find resolutions to most problems though.

My USB thumb drive can not be mounted as the Superblock can't be read. I would use Windows to reformat the drive however, I would like to keep the data on the drive if possible.

Error Message: Error mounting: mount: /dev/sdc: can't read superblock

I have been Googling for a while and came across the below some ideas that I then tried.
The commands and the results are below. Commands are in bold.

I gather that the first one only lists partitions(?) on the drive but I thought someone might find it more helpful than I do.

sudo fdisk -l /dev/sdc

Disk /dev/sdc: 8103 MB, 8103395328 bytes
250 heads, 62 sectors/track, 1021 cylinders, total 15826944 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x6f20736b

This doesn't look like a partition table
Probably you selected the wrong device.

Device Boot Start End Blocks Id System
/dev/sdc1 ? 778135908 1919645538 570754815+ 72 Unknown
/dev/sdc2 ? 168689522 2104717761 968014120 65 Novell Netware 386
/dev/sdc3 ? 1869881465 3805909656 968014096 79 Unknown
/dev/sdc4 ? 2885681152 2885736650 27749+ d Unknown

Partition table entries are not in disk order

dumpe2fs /dev/sdc1 | grep superblock
dumpe2fs 1.41.14 (22-Dec-2010)
dumpe2fs: No such file or directory while trying to open /dev/sdc1
Couldn't find valid filesystem superblock.
This one (below) brings up another window (some kind of disk management?) but I can't select /dev/sdc (the USB thumb drive)

sudo pysdm
[sudo] password for <Insert Username Here>

(pysdm.py:4897): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(pysdm.py:4897): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(pysdm.py:4897): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",

(pysdm.py:4897): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap",
I have also had a read of this article here (http://linuxexpresso.wordpress.com/2010/03/31/repair-a-broken-ext4-superblock-in-ubuntu/) (Linux Expresso). However, I can't figure out how to transpose it to FAT32.

Any ideas?

[TeoBigusGeekus]

Try checking the partitions for errors and correcting them with fsck:

sudo fsck /dev/sdc1
sudo fsck /dev/sdc2
sudo fsck /dev/sdc3
sudo fsck /dev/sdc4

[JediMasterOdd]

Thanks for the suggestion, but it's apparently not available.

This is the same for /dev/sdc1, 2, 3 and 4

sudo fsck /dev/sdc1
[sudo] password for <insert Username Here>:
fsck from util-linux 2.19.1
e2fsck 1.41.14 (22-Dec-2010)
fsck.ext2: No such file or directory while trying to open /dev/sdc1
Possibly non-existent device?
However...


sudo fsck /dev/sdc
fsck from util-linux 2.19.1
dosfsck 3.0.9, 31 Jan 2010, FAT32, LFN
There are differences between boot sector and its backup.
Differences: (offset:original/backup)
65:01/00
1) Copy original to backup
2) Copy backup to original
3) No action
? 2
/
Contains a free cluster (2). Assuming EOF.
FAT32 root dir starts with a bad cluster!

[killermist]

Is the Filesystem something other than ext2/3/4? Like xfs, jfs, reiser(4)?
If so, then doing checks for ext2/3/4 will obviously fail.

[killermist]

Try this:

sudo su
for count in 1 2 3 4; do mkdir /mnt/sdc$count; mount /dev/sdc$count /mnt/sdc$count; done
exit

paste the output (which should show any mount failures or whatnot), and also the output (after the command string) of

df -hT

[JediMasterOdd]

As requested:

for count in 1 2 3 4; do mkdir /mnt/sdc$count; mount /dev/sdc$count /mnt/sdc$count; done
mount: special device /dev/sdc1 does not exist
mount: special device /dev/sdc2 does not exist
mount: special device /dev/sdc3 does not exist
mount: special device /dev/sdc4 does not exist



df -hT
Filesystem Type Size Used Avail Use% Mounted on
/dev/sdb1 ext4 36G 2.9G 32G 9% /
udev devtmpfs 2.0G 12K 2.0G 1% /dev
tmpfs tmpfs 793M 964K 792M 1% /run
none tmpfs 5.0M 0 5.0M 0% /run/lock
none tmpfs 2.0G 200K 2.0G 1% /run/shm

[killermist]

Is the drive a USB (or other external connected) drive? Because the output of the commands indicates that the drive is not where it was when you were originally issuing it commands.

[JediMasterOdd]

Yes, It's a USB memory stick. It's meant to be FAT32

[killermist]

With it (potentially) changing places quasi-randomly, I can't give you specific commands.
If you know what the root device is that it moved to (like sdd or sde instead of sdc), you can substitute that in the commands I gave you, and that will give some useful output, hopefully.
Of course, some quasi-failed attempts could start to populate your /mnt directory with subdirectories you may never use. Though as unused/unpopulated directories their mere existence shouldn't harm anything.

[JediMasterOdd]

Sorry I have not replied earlier. I have been on holidays.

I have rerun the following script, specifically targeting the USB device (now /dev/sdb)

df -hT /dev/sdb
Filesystem Type Size Used Avail Use% Mounted on
udev devtmpfs 996M 4.0K 996M 1% /devWhen I ran the below script, I had to break it up line by line as I have no idea how to make a script, so I may have given a false reading

sudo su
for count in 1 2 3 4; do mkdir /mnt/sdc$count; mount /dev/sdc$count /mnt/sdc$count;
done exitDo you have a link with instructions for creating scripts?

Is it possible to copy a Superblock from another USB device to the corrupt one?

[killermist]

The operant line is:

for count in 1 2 3 4; do mkdir /mnt/sdb$count; mount /dev/sdb$count /mnt/sdb$count; done
"sudo su" just grabs superuser privileges (because you need them to create the directories and try the mounts)
and "exit" after executing the line just drops the superuser privileges, returning you to standard user again.

[JediMasterOdd]

Thanks :)


for count in 1 2 3 4; do mkdir /mnt/sdb$count; mount /dev/sdb$count /mnt/sdb$count; done
mount: special device /dev/sdb1 does not exist
mount: special device /dev/sdb2 does not exist
mount: special device /dev/sdb3 does not exist
mount: special device /dev/sdb4 does not exist



df -hT /dev/sdb
Filesystem Type Size Used Avail Use% Mounted on
udev devtmpfs 996M 4.0K 996M 1% /dev

[JediMasterOdd]

Well, I have found the data I was trying to save, hidden away in a Hard Disk image I took a while ago.

Thanks for your efforts and ideas. I think I'll just reformat the USB drive