ext3 partition can not be mounted as ext3 but as ext4

Theodore Tso tytso at mit.edu
Wed Feb 20 13:44:33 UTC 2008

On Wed, Feb 20, 2008 at 02:03:41PM +0100, Gunter Zenkl wrote:
> After my NAS (QNAP TS109 with embedded Linux) behaved a bit strange, I 
> removed the hard disk (Seagate 500GB) and made a 1:1 image of the whole 
> drive with dd_rescue on my desktop. I worked on the image from here on 
> forward. The kernel version of the QNAP TS109 is at least 
> probably something newer.

That seems.... very strange.  Either your filesystem is horribly
corrupted, or your NAS box did something very unusual.  Do you have a
hard drive image from a working NAS box that is known good, so we can
see if they are doing something strange the ext3 filesystem format.
(I doubt they are using ext4 as well, but maybe they grabbed some
feature flags because they did do something wierd with the filesystem
format with some kind of private extension?  Unlikely, but we can't
rule it out.)

Another approach would be to get the sources for the kernel from the
NAS manufactuerer (which must be available per the GPL) and diff
against the baseline kernel to make sure they didn't do something
wierd with the filesystem code.

> Oh and debugfs on the ext4dev mounted partition gave:
> -----------------------------------------
> root at grml ~ # debugfs /mnt/floppy
> debugfs 1.40.3 (05-Dec-2007)
> /mnt/floppy: Attempt to read block from filesystem resulted in short read 
> while opening filesystem
> debugfs:  stats
> stats: Filesystem not open

You need to run debugfs on the device, not on the mounted partition:

i.e., "debugfs /dev/sdd3".  You mist also try using catastrophic mode
("debugfs -c /dev/sdd3") if the first invocation doesn't work.

Good luck!

						- Ted

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