Nut and RAID on FreeBSD 7.0

Derrick Ryalls ryallsd at
Wed Jan 9 16:51:22 PST 2008


I have a RAID fileserver plugged into a UPS and nut is able to
communicate with it successfully.  With the winds making the lights
flicker, I started looking into having the computer shut down when
power goes out for more than say 5 minutes or so.  Looking at the
documentation, I found that the 'true' solution is more like the
system goes into a safe state when the battery gets low, then the ups
eventually dies.  When power is restored, the UPS and computer are
supposed to both come back to life.  This would be a great system to
have in place, but it does sound a bit risky and so may not be worth
doing just to save my home fileserver.

The instructions and the conf file have the shutdown command of
'shutdown -h +0' which will halt the system.  The man page for halt
says the the disk cache will be flushed, but doesn't mention anything
about going to read-only or anything.  I suppose my first question is
whether or not flushing the cache is sufficient to save the RAID (5)
array, or if I need to find a way to get the file systems into read
only mode?

The second question has to do with a rc.d script that nut recommends
creating.  The script does a 'upsdrvctl shutdown' and then a sleep
120, basically waiting for the machine to die while in the script.
Won't this block the other rc.d scripts?  Also, is this the magic part
that enables the machine to auto power up when power is restored?

Changing the shutdown command in nut to 'shutdown -p +0' looks like
the sure fire way to get the system down clean before the power is
lost, but if my concerns are not valid, then I could be missing out on
some nice functionality for no reason.

Does anyone have experience with this?

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