Re: ext3 corruption

From: Molle Bestefich
Date: Wed Aug 09 2006 - 19:07:15 EST


Duane Griffin wrote:
> How close to 1-1 does "-n" relate to non-"-n" ?
>
> For example, does e2fsck take into consideration the changes it would
> have done itself in regular mode when it proceeds to the next problem
> and/or phase of a -n operation?

It corresponds perfectly to you answering "no" to all questions :)
Sorry, I don't have a much better answer than that.

A good answer, even if it's one that can be found in the manual :-).

> If it doesn't, then that command is, well, totally useless.

That is too strong.

I don't think so.

If it doesn't take into account own changes, then the -n command is
unable to produce even a slightly accurate resemblence of what would
happen if I did a real run.

And that's about the only use case I can come up with for -n...

You should be able to get an idea how severe the damage
is, at least.

If it's complete inaccurate, I can't trust the result, so that doesn't
help me much, if any.

From a quick read of the code it looks like your problem
is related to dodgy data in the superblock, and e2fsck will attempt to
recover & continue by reading the backup superblock.

Thanks a lot for checking !

I wonder then, will it write back this alternate superblock?

Is there anything I can do to control the process, like:
Do a test mount with one of the alternate superblocks?
Tell fsck to test a specific superblock; afterwards tell fsck to use a
specific superblock?

That would be useful.

It does that regardless of whether you use -n,
so in that respect at least it will operate in the
same way as "normal" operation.

Ok, that's very good to know, thanks a lot.
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