Subject: Re: recovering from a bad crash, ffs recovery
To: None <netbsd-users@netbsd.org>
From: Manuel Bouyer <bouyer@antioche.lip6.fr>
List: netbsd-users
Date: 01/08/2004 21:27:06
On Tue, Jan 06, 2004 at 03:17:22PM -0500, Charles Shannon Hendrix wrote:
> Tue, 06 Jan 2004 @ 00:44 +0100, Manuel Bouyer said:
> 
> > > Maybe a tool to tell ffs to use an alternate superblock or something?
> > 
> > Well, no. What you really needs to is to play with fsdb now.
> 
> I have no idea what to do with that.
> 
> I did run it and look around, but I'd cause more damage than help.
> 
> I ran a restore of a dump from last year from a 4mm DDS2 tape, and it
> worked fine.

Over the same drive, or a different one ?

> 
> This is an archive drive with 12+ years of misc files.  The reason it is
> a loss is because of the years of time it took to collect the files, and
> some of them are archives of stuff no longer available on the net.
> 
> Now that I have it updated as of last year, the loss is not so painful.
> 
> I'd like to recover the last year of updates, but is it feasible to
> do this with fsdb?

I think it is but I'm not sure exactly how ...

> 
> I scanned for superblocks with vim and read through all the deleted
> directories and files... is there any way to reactivate the metadata
> with fsdb quickly?

Not quickly. I'd probably require an automated tool, but I don't know how
to do it.
The main problem is directory entries. We need to recover dp->d_namelen,
and I can't see how to do this safely in an automated way.
Once we have that we need tools to scan directories entries, and for each
of them mark the inode and associated blocks as non-free.

Would be interesting to have such a tool, but I don't know of any existing
yet.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 23 ans d'experience feront toujours la difference
--