Two days ago "someone" took out brutally (but without intention) the power supply of my box; when I reboot the machine I've got this message just after the Grub was loaded:
No init found. Try passing init= boot arg
BusyBox v1.10.2 (Ubuntu 1: built-in shell (ash)
Mmm, I've never seen this, but I quickly understood that my box was seriously damaged, the access to my data was impossible; user in panic

After two days of trying to fix the issue I've been able to get back my disk intact; I know, I'm a pretty lucky folk.

First to all this "guide" worked for me and for my case; for what I've understood the problem was regarding something about EXT4 filesystem that was locking the access to the disk due to the unexpected shutdown (of course); Grub was ok, hardware disk was ok; I'm not so deep involved in the knowledge of the filesystem stuff, but I had the high suspect that the inode structure was denying the system to be mounted/accessed for some pending operations.

At this moment I've created a USB key with the live of Ubuntu Rescue Remix and I booted the machine with this distro.

As a first step I've just list my partitions (sda in my case it's the only drive):
sudo fdisk -l /dev/sda

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000619b6

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       29844   239721898+  83  Linux
/dev/sda2           29845       30401     4474102+   5  Extended
/dev/sda5           29845       30401     4474071   82  Linux swap / Solaris
The damaged partition, in my case, was /dev/sda1.
Now I've tried to do an fsck:
sudo fsck -yv /dev/sda1
fsck: Device or resource busy while trying to open /dev/sda1
Filesystem mounted or opened exclusively by another program?
What? The disk was obviously not mounted (although I did an umount); no way, I was not able to do an fsck on that partition.

I've tried everything:
  • Create an image with dd and mount the image after an fsck (the image was unusable due to an arror in the filesystem)
  • Back-up the partition with PhotoRec (the files saved were really trivial)
  • Mount the disk as slave (the Ubuntu Rescue freezed trying to mount it)

I've was almost to give up and prepare myself to format the disk, when I came across this technical document (for EXT3)
So I decided to try it as last resource (remove the first inode), based on consideration that all my data was already lost.
sudo debugfs -w /dev/sda1
debugfs 1.41.11 (14-Mar-2010)
debugfs:  clri <8>
debugfs:  quit
Then I've launch fsck:
sudo fsck -yv /dev/sda1
fsck: Device or resource busy while trying to open /dev/sda1
Filesystem mounted or opened exclusively by another program?
Damn! No way; but I was thinking that maybe a reboot (*) was needed.
(*) to reboot with Ubuntu Rescue I've used ALT+PrnScreen+r+e+i+s+u+b instead of normal reboot because the normal reboot was not working

Then I've launch fsck again:
sudo fsck -yv /dev/sda1
and now this time worked!
Fsck fix the filesystem errors; I've had not need to do a tune2fs as stated in the document reported above for the re-creation of the journalized filesystem.

Rebooted the machine with my disk and everything is all there.
Happy user.