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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!

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Well, hopefully you have backups. – Olli Mar 4 '11 at 14:02
@Olli no i don't have backups :( ! – Santosh Linkha Mar 4 '11 at 14:10
What does dmesg | tail -20 say after you have unsuccessfully tried to mount the partition? – arrange Mar 4 '11 at 15:34
@arrange i am a ubuntu layman !!! – Santosh Linkha Mar 5 '11 at 5:08
up vote 3 down vote accepted

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

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