Summary: 2 Corrupted Disk Recovery Questions: After the fact

From: Greg Freemyer <freemyer_at_NorcrossGroup.com>
Date: Fri, 25 Jan 2002 18:26:08 -0500

Original question at the bottom.

Thanks to Shane Southwood, Shawn Keller, Robert Weirick and Pat O'Brien

I have not had a chance to test anything yet, but the answers are:

1) In general try using btcreate/btextract. It works great for these kinds of situations.

2) For what I thought was a corrupted bootstrap, it was really a missing /osf_boot. I had never noticed this little file in the root directory. It is apparently loaded before /vmunix. If I would have known this, I could have just copied it from the CD to the disk (once I had it mounted).

3) For creating the /dev/tape/tape0 device I should have done a "hwmgr -scan" instead of dsfmgr -K. Possibly a /dev/MAKEDEV tz# or /dev/MAKEDEV rmt# would help as well.

4) For those that don't know, to mount a root AdvFS filesystem, the command is "/sbin/advfs/advscan -r dsk0; mount -t advfs domain_dsk0#root /mnt"

The most interesting part of the above to me is the /osf_boot file. I gather that booting involves:

a) Executing the bootstrap file that is written by disklabel.
b) It in turn runs /osf_boot
c) /osf_boot runs vmunix (or genvmunix, or whatever you pass in to your boot command).

I never knew about that /osf_boot step.

Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
The Norcross Group
www.NorcrossGroup.com

=================
Managers,

Yesterday, we had a major screw-up. A technician mistakenly pulled the power plug on a running production DS-10.

I think the bootstrap code and part of the root filesystem got damaged.

Note being sure what to do, I re-installed the OS from CD (Tru64 V5.0) and read in my backups. So life is Okay, but we were down for far too long.

If I would have known how to do it, I would have preferred to:

1) Boot from the OS CD and get a prompt.

2) Re-write the bootstrap loader.

3) Mount the root drive as /mnt

4) Restore my root backup.

I don't know how to do 2 or 4 .

2) I suspect can be done with disklabel, but I did not want to blow away the data already on the disk.

4) requires a /dev/tape/tape0 type device (the server has a internal DAT drive), I tried to create it with dskmgr -K, but it did not work.

Details on how to write a bootstrap and access a tape drive while booted from the OS CD would be appreciated.

Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
The Norcross Group
www.NorcrossGroup.com
Received on Fri Jan 25 2002 - 23:30:06 NZDT

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