How to retrieve data from a corrupted volume

Question

My Ubuntu 10.10 just crashed, probably due to hardware error (and in the end I was getting errors like Unknown filesystem ..... grub> .., and it went to the GRUB console before I could take any other action).

I reinstalled the same version from a USB stick. I had Ubuntu installed with the ext4 file system and I also have the same filesystem in the same hard disk on a different drive.

When I try to access my previous filesystem, I get errors:

Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sda6,
   missing codepage or helper program, or other error
   In some cases useful info is found in syslog - try
   dmesg | tail  or so

I had some important files in the previous volume ; I don't know how to retrieve them.

And what are the chances that I would get the same outcome (hardware error)? Please help me!

Answer 1

Try ddrescue to make an image of your failing drive/partition. Then use foremost on the image you made to try and save files.

As you say you're a layman, that would mean running, these commands:

ddrescue -i0 -s50M /dev/sda6 image.dd logfile
ddrescue /dev/sda6 image.dd logfile
ddrescue -d -r3 /dev/sda6 hdimage.dd logfile

Good information on how to use ddrescue on its documentation page.

After that, try foremost on the image:

foremost -i image.dd -t all -o savedfiles -v

Answer 2

If it is a hard drive failure SpinRite (www.grc.com) may be your only hope for disk recovery.