Superblock read error| Diagnosing correct ext file system | Surviving fsck.ext3.ext4 messages in Precise Pangolin 12.04.

Finally it happened. My laptop was a bit slow yesterday evening as also in the morning. In the evening it simply did not boot. It has Precise Pangolin 12.04 with Cinnamon. Unity has not been removed. The message it displayed was:

General Error mounting filesystem.
A maintenance shell will now be started.
Control-D will terminate this shell................
sulogin.............etc. etc.

Apparently the disk could not be read. A typical File system error. After the boot loader hands over the command to OS, the first thing it reads from disk is called “Superblock” which includes the disk’s geometry information, available free space, and most important is the location of the first i-node i.e. beginning of disk.

Now I rebooted with Puppy Linux (A 200 MB Distro with everything we need) but it could not find Wifi radio driver on the Dell XPS laptop but it booted well and quick. Puppy did not have fsck.ext3 command. So I rebooted with Knoppix and tried this command on the Terminal:

       fsck.ext3 -n /dev/sda2

This was the output:

"Superblock could not be read or does not describe correct ext2 
filesystem. If the device is valid and really contains an ext2
filesystem (and not swap or ufs or something else), 
then superblock is corrupt, and you might try
...............alternate superblock"

fsck.ext4 helpIt also suggested a command with alternate superblock number but that could have ruined harddisk. It did once earlier. “fsck –help” was not helpful either. Actually it was but message was hidden and I did not notice the relevant part earlier.  So how I survived this time? Continue reading