OpenBSD-4.6/sbin/scan_ffs/scan_ffs.8

.\"	$OpenBSD: scan_ffs.8,v 1.16 2008/03/23 23:28:46 krw Exp $
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.\" Copyright (c) 1997 Niklas Hallqvist, Tobias Weingartner
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.\" .TH scan_ffs 8
.Dd $Mdocdate: March 23 2008 $
.Dt SCAN_FFS 8
.Os
.Sh NAME
.Nm scan_ffs
.Nd find UFS/FFS partitions on a disk
.Sh SYNOPSIS
.Nm scan_ffs
.Op Fl lsv
.Op Fl b Ar begin
.Op Fl e Ar end
.Ar device
.Sh DESCRIPTION
This is the life-saver of typos.
If you have ever been working too long,
and just happened to type 'disklabel -w sd0 floppy', instead of 'disklabel
-w fd0 floppy', you know what I am talking about.
.Pp
This little program will take a raw disk device (which you might have to
create) that covers the whole disk, and finds all probable UFS/FFS partitions
on the disk.
It has various options to make it go faster, and to print out
information to help in the reconstruction of the disklabel.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b Ar begin
Tell
.Nm
where to begin searching for filesystems.
This makes it easier to skip swap
partitions, or other large non-UFS/FFS partitions.
.It Fl e Ar end
Ditto for telling
.Nm
where to stop.
.It Fl l
This will make
.Nm
print out a string looking much like the input to disklabel.
With a little massaging, this output can usually be used in the disklabel edit.
.It Fl s
This tells
.Nm
to be smart about skipping partitions (when it thinks it found a valid one).
By not scanning partitions for superblocks, the program completes a couple of
orders of magnitude faster.
However, sometimes being smart is too good for
its own good,
especially if your disk has had a different layout previously, or contains
other non-UFS/FFS filesystems.
.It Fl v
Tell
.Nm
to be verbose about what it is doing, and what it has found.
.It Ar device
This specifies which device
.Nm
should use to scan for filesystems.
Usually this device should cover the whole disk in question.
.El
.Pp
The basic operation of this program is as follows:
.Bl -enum -width "1111"
.It
Panic.
You usually do so anyways, so you might as well get it over with.
Just don't do anything stupid.
Panic away from your machine.
Then relax, and see if the steps below won't help you out.
.It
Try to find your old disklabel by any other means possible.
This includes
printouts, backups
(look in
.Pa /var/backups/ ) ,
screendumps, and whatever other method you can think of.
The more information you have, the better your chances are in recovering the
disklabel of the disk.
.It
Create a disklabel on the affected disk, which covers the whole disk, and has
at least one partition which covers the whole disk.
As the
.Dq c
partition
usually covers the whole disk anyways, this sounds like a good place to start.
.It
Run
.Nm
over this partition.
If you have any information about the disklabel
which used to exist on the disk, keep that in mind while
.Nm
spews out its things.
.It
Use
.Xr disklabel 8
to reconstruct the disklabel on the affected disk, using
all the information you gathered from
.Nm
and other sources.
.El
.Pp
Last but certainly not least, we wish you good luck.
The UFS/FFS filesystems are pretty sturdy.
I've seen them reconstructed after some pretty weird and
awesome fumbles.
If you can't have backups, at least have funky tools to help
you out of a jam when they happen.
.Sh SEE ALSO
.Xr disklabel 8
.Sh BUGS
It is not perfect, and could do a lot more things with date/time information
in the superblocks it finds, but this program has saved more than one butt,
more than once.