Mirroring the root disk of already installed machine

[Mike Meyer]

In <20060908100337.73c0c88d.vlady at gbservices.biz>, Vladimir Terziev <vlady at gbservices.biz> typed:
> 	i have a machine running FreeBSD 5.4 . It has 2 HDDs. Recently the non-root HDD failed and lost all the data on it. Since the machine is working 24/7 i want to mirror its root disk (this one with the OS on it) in order to prevent a severe downtime and data loss.
> 
> 	Is there a safe way to do the above using gmirror ?

Yes. I started doing it on FreeBSD 5.5. It's pretty simple: shut down
to single user. Create a mirror with your root disk in it. Edit
/etc/hosts to change the device name from ad* to
mirror/*. Reboot. Once you're back up, add the second disk to the
mirror. If you want exact instructions, consult google. The tricky
part is creating the initial mirror on a mounted file system - you
have to toggle a sysctl (I think that's what it was) to do that. Some
directions include that; others recommend you boot on a recovery CD to
create the mirror initially.

BTW, this probably should have gone to -questions.

	<mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.