Re: [BUG] e2fsprogs & ext2/3 behave poorly with corrupt group descriptors

On Wed, Aug 23, 2006 at 04:46:36PM -0600, Andreas Dilger wrote:
> What about using one of the backup group descriptors?  I'm not sure about
> e2image, but e2fsck should try that automatically (older versions were
> worse at that, and if there is still a problem for e2fsck to find backups
> this should be fixed).  The kernel can be told to use a backup with
> "-o sb=32768" (or 32768 * {3,5,7}^n) when mounting (assuming 4kB blocksize).

Doesn't particularly seem to help in mounting the filesystem:

[root@woody spare]# mount -t ext2 -o loop,ro,sb=8277 laptop.img mnt/
EXT2-fs: loop0: couldn't mount because of unsupported optional features (4).    
...
[root@woody spare]# mount -t ext3 -o loop,ro,sb=8277 laptop.img mnt/
EXT3-fs error (device loop0): ext3_check_descriptors: Block bitmap for group 0 !
EXT3-fs: group descriptors corrupted!                                           

but then I might not be providing the right superblock number; it's just 
what I found in the filesysetem dump.  At the very least e2image needs to be 
taught to do the right thing with this sort of corruption.

		-ben
-- 
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