Ext4 file system corruption and possible data loss

[Ari Torhamo]

Hello,

Thanks Markus for your reply. The problem with this non-booting Ubuntu
9.10 system has turned out to be serious. I connected the hard disk it's
installed on to my own computer to test it, and found out that both ext4
partitions on the disk are more or less unreadable. Gnome disk utility
says that the /home partition is "unknown or unused" and it also isn't
visible in Nautilus. The system partition is shown as "Linux ext4
(version 1.0)", but the content cannot be read (the lost+found folder is
there, but I'm not able to set the permission to myself - and there's no
user data on that partition anyway).

I ran "fsck.ext4 -pfv" for both partitions (I'm not familiar with this
tool, so I may have done something wrong), and I got the following
results.

Home partition:

..............................

sudo fsck.ext4 -pfv /dev/sdb5

   15256 inodes used (0.03%)
     281 non-contiguous files (1.8%)
       5 non-contiguous directories (0.0%)
         # of inodes with ind/dind/tind blocks: 0/0/0
         Extent depth histogram: 15116/128
 4623284 blocks used (2.08%)
       0 bad blocks
       1 large file

   13343 regular files
    1902 directories
       0 character device files
       0 block device files
       0 fifos
       0 links
       2 symbolic links (2 fast symbolic links)
       0 sockets
--------
   15247 files

.............................

System partition:

.............................

ari at mung-papu:~$ sudo fsck.ext4 -pfv /dev/sdb6

      11 inodes used (0.00%)
       0 non-contiguous files (0.0%)
       0 non-contiguous directories (0.0%)
         # of inodes with ind/dind/tind blocks: 0/0/0
         Extent depth histogram: 1
   99190 blocks used (2.71%)
       0 bad blocks
       1 large file

       0 regular files
       2 directories
       0 character device files
       0 block device files
       0 fifos
       0 links
       0 symbolic links (0 fast symbolic links)
       0 sockets
--------
       2 files

..............................

When I tried to re-install Ubuntu to the problematic system partition,
the following error message was shown right after the installation
started:

"Failed to remove conflicting files
The installer needs to remove operating system files from the install
target, but was unable to do so. The install cannot continue."

I also tried to remove and recreate the system partition before
installing, but got the same error message anyway. 

I run a thorough test for the hard disk, and no errors were found.
Complete run of Memtest showed no errors either (in the computer that
the hard disk belongs to). The Windows installation on the disk works
without problems.

The motherboard on the computer is Asus M4A78T-E and the processor is
AMD Phenom 2 X4 955. Before this problem the installation had been in
use for a couple of months and working well. As I told in my previous
message, the  problem started when the machine was booted for the first
time after installing the updates that became available on Tuesday 5th
of January (or so) two weeks ago (can't know of course, if there's a
connection).

What might be the next step to try to get the /home partition readable?
It's been more than a month since the user did the last back-up, so some
data will be lost, if there's no success. Of course it would be
important to know what lead to this situation too, as the reliability of
the operating system (using the word in the broad meaning) might be in
question.

Thanks

-Ari-