Re: ext2fs repairs

Thomas E. Dodd /CSDC (ted@cypress.com)
Tue, 19 Jan 1999 13:50:24 -0600

Guest section DW wrote:
>
> From: "Thomas E. Dodd /CSDC" <ted@cypress.com>
>
> I boot 2.2pre6 with a new CPU (686MX from 686).
> First boot was fine. Went to Win9x to check new CPU,
> fine. Reboot 2.2. Unable to mount /var (ext2fs on hdb2)
> Ran fsck complained bad-super block. Ran with -b 8193,
> fixed errors, mounted fine. Rebooted to check.
>
> Failed to mount /var again. Now fsck, mount, and other
> ext2fs utils say not a valid ext2fs, bad magic number.
> I tried fsck again with trhe first 10 superblocks,
> and get the same results.
>
> Looking at results of 'dd if=/dev/hdb2 bs=1024'
> the magic number is the same as a good ext2fs (0xEF53)
> at same offset from begining of partition.
>
> Any ideas what is wrong?
> How to fix?
>
> -Thomas
>
> The way you present things here it sounds as if Win9x did
> something to the superblock. That is possible, such things
> have been seen before. But of course something else may
> have been wrong, and the intermediate booting of Win9x
> might not have had anything to do with these fs problems.

Windows doesn't see the drive or the partition, so it didn't
get to the filesystem.

> It is a pity that you did e2fsck. (My experience is that
> when things are mildly broken, e2fsck fixes everything fine,
> but when things are badly broken e2fsck makes things even worse.)

I thought it was mild:(

> If there are no valuable data on this disk, so that you can play
> with it, perhaps you could try to repeat the procedure?
> Make a fresh ext2 filesystem on the same partition as before,
> Save the partition table and the first 100 blocks or so of this
> ext2 partition. Perform the same actions. Report reproducible
> results.

It happened once befor on a different drive but still /var.
So I moved it. the other disk is still fine and this one
was before. I can't force it to happen at will, but it
has happened before.

> My first conjecture would be that nothing is wrong with Win9x

I agree

> maybe this new CPU was overclocked or so. If you get reproducible
> problems, do these go away if you use a different CPU?

No. The previous time was a different CPU.
Not overclocked.

I need a way to recover the data. I need the logs and info
for RPM. I don't have enough room to backup and reinstall,
then restore my changes.

Anyone know the ext2fs well enough to help?

-Thomas

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