Hello folks
I've come across a problem on a friend's computer.
The computer is fairly old (see below), running Ubuntu 10.10, with / on 
a 40GB IDE drive, and /home on a 120GB Maxtor SATA drive.
It's /home that's the problem.  It's on a single partition /dev/sda1, 
formatted as ext4.  I've run the Maxtor diagnostics on the drive, and no 
problems were reported.
Ubuntu wants to check the filing system on every boot.  Running 'fsck 
-f' manually (from Knoppix 6.2) gives:
   Block bitmap differences: <some number ranges, different each time>
Sometimes it also offers to fix:
   Free blocks count wrong for group #<numbers that change each time>
I choose to fix those problems, but they're still there next time.
I've also run 'fsck -fc /dev/sda1' -- it didn't report any bad blocks, 
and the other were still there.
So I rsync'd all the files to an external hard drive, recreated the 
filing system with
   mkfs.ext4 /dev/sda1
and fsck'd the empty filing system -- it was fine.
I then rsync'd the data back with
   rsync -av <backup dir> /dev/sda1
ran fsck again, and the errors have returned!
Why would copying data into a filing system cause errors like that?
Googling hasn't turned up anything useful.
As I mentioned, the PC is old, and a few capacitors on the motherboard 
are looking a bit swollen, so I would accept the possibility of random 
freezes or other weirdness.  But this doesn't seem like randomness -- 
it's consistently wrong.
cheers
Chris
-- 
Chris Dennis                                  cgdennis@???
Fordingbridge, Hampshire, UK