find UFS/FFS partitions on a disk
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.
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.
The options are as follows:
scan_ffs where to begin searching
for filesystems. This makes it easier to skip swap partitions, or other
large non-UFS/FFS partitions.
- Ditto for telling
scan_ffs where to
- This will make
scan_ffs 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.
- This tells
scan_ffs 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.
scan_ffs to be verbose about what
it is doing, and what it has found.
- This specifies which device
should use to scan for filesystems. Usually this device should cover the
whole disk in question.
The basic operation of this program is as follows:
- 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.
- Try to find your old disklabel by any other means possible. This includes
printouts, backups (look in
/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.
- 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
“c” partition usually covers the whole disk anyways, this
sounds like a good place to start.
scan_ffs over this partition. If
you have any information about the disklabel which used to exist on the
disk, keep that in mind while
spews out its things.
- Use disklabel(8) to
reconstruct the disklabel on the affected disk, using all the information
you gathered from
scan_ffs and other
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.
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