Memory requirement for fsck_ffs in recovery session

Polytropon freebsd at
Tue Aug 19 22:26:50 UTC 2008

On Tue, 19 Aug 2008 14:45:18 -0400, Lowell Gilbert <freebsd-questions-local at> wrote:
> Polytropon <freebsd at> writes:
> > I always thought I needed to modify the
> > file system so fsck_ffs could do its job, now I think I rather would
> > modify fsck_ffs so it would skip these errors I can't see any reason
> > for.
> I'm not following your logic, but I suspect you're jumping into
> dangerous waters here...

I think so, too, but that's the only way I think I can recover
at least a part of my files without buying an expensive and "Windows"
based recovery program or even sending the harddisk to a recovery
service for 50 times the price of a new harddisk.

I found out that fsck_ffs version 7 seems to stumble at incorrectly
read or processed variables maxino and lastvalidinum. After "removing"
these obstacles from the source code fsck seemed to process further,
but did not reach the point where collected inode data would be
restored into the lost+found/ directory. This is what I do expect.

> > Out of curiosity, I booted my system with a done version 5 installation
> > harddisk I had extracted from a system some years ago, and guess what?
> > fsck_ffs version 5 seemed to do more than version 7 did! This is what I
> > get:
> >
> > 	fsck_ffs: cannot alloc 1073796864 bytes for inoinfo
> >
> > My question: My machine has 768 MB RAM (512 + 256 MB SDR-SDRAM) and
> > fsck_ffs seems to request 1 GB RAM (1073796864/1024/1024/1024). Is
> > it possible to provide this amount of RAM via a harddisk backed RAM
> > disk or a swap partition?
> Swap should be fine; the allocation is just a regular calloc(3) call.

So I should assert a swap partition big enough; /dev/ad2s1b should
be fine for this.

> > I think I'll try ffsck_ffs version 6 from a PC-BSD installation that
> > must be somewhere around here...
> Not likely to help, but since you aren't working with the original
> disk, you don't have much to lose by trying...

That's why I'm glad (haha) that dd replicates the error 1:1.
Maybe fsck_ffs version 6 behaves differently than 5 or 7.

If I gathered more information and did try some more things,
I may bring up my most sad problem here again.

And: No, I didn't have a backup. :-(

>From Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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