Recovering files after a crash

[Roland Smith]

On Wed, Aug 19, 2009 at 09:59:32AM +0200, Erik Norgaard wrote:
> Thanks, I couldn't decipher these GEOM_LABEL messages, nice to know that 
> I can stop worrying. But for future incidents, the second question remains:
> 
> 1. How do I best protect my system from disk errors in case of a crash?

One word: _backups_!

Multiple solutions are possible. You can have two disks in RAID1 (mirroring,
which is like instantaneous backup). Or you can have two disks where the
second is kept up-to-date by rsync running from cron (this also gives you a
limited undo functionality if you accidentaly delete a file). Ar you can back
up to a NAS, USB connected disk or to tape.

> I have a headless system with no spare head to attach and doing 
> single-user blind-folded is further complicated by the fact that I'm not 
> native to the US keyboard layout, so my top priority is that it boots.

If you can connect it to another system (that has a monitor) via a serial
null-modem cable and you enable the serial console (see the Handbook), you can
watch the boot process from the other system.

If you don't have anothe machine closeby, you should get a network-accessible
KVM switch with serial connectors. [maybe something like this:
http://www.knuerr.com/web/en/products/kvm/kvm-switch-dominion-ksx.html] 
With such a switch and the serial console you should be able to watch the boot
of the machine remotely.

> 2. When you have lost inodes or similar errors and stuff ends up in 
> lost+found, how do you figure out what it was and recover the lost files?

You have to look at the contents of the files in lost&found. Usually it is
easier to restore from backup.

> Is there a FBSD crash guide?

Not that I know of. The only guidance that really matter would be "make sure
you have backed up critical data". No need for elaborate guides. :-)

Roland
-- 
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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