recovering disks with trashed labels

[Operator]

> problem is as follows
> We had a Sun 3/180 with a single Eagle disk drive.  One day the machine
> spontaneously crashed and refused to boot.  After mounting another drive
> and reloading from the distribution tapes, I tried to mount one of the
> partitions on the failed disk to no avail.  The sunos formatter said the
> lable is corrupted.  I need to know if there is any way to get the
> information off the disk.  I'm not sure where to proceed from here.

By your description, it sounds like the disk label is gone. The data
that was on the disk may or may not still be there, but here are some
things you can try:

1) if you know what the partition map was before the crash, simply restore
it using format(8s), and if your data is there you should be okay (with
maybe a few fsck's). 

2) if you haven't tried recovering the label from format(8s), you should.
This is done by spinning up the damaged disk on the system, not as the
boot disk, running format, and then selecting the "backup" command from
the format menu.  If your backup labels exist, this will find them and
replace your primary labels.

3) if you have access to the source fro fsck, you can do what I did
(pre-format(8s)) when the same thing happened to me: hack the part of the
program that checks for superblocks so that it checks every block until it
finds one.  If the filesystems aren't trashed, this method works just
fine. If you don't have the source, I may be able to let you have a
binary.  However, this may be illegal.  If you ask, I'll check into it.

Mark Hickey          Computervision Division
O/S Development      Prime Computer, Inc.
                     Bedford, MA     01730

UUCP    : {decvax|linus|sun}!cvbnet!mhickey
Internet: mhickey at cvbnet.prime.com