Date: Fri, 28 Dec 2001 00:24:34 +0100 From: Thomas Quinot <thomas@cuivre.fr.eu.org> To: Garance A Drosihn <drosih@rpi.edu> Cc: freebsd-current@FreeBSD.ORG Subject: Re: reboot -p Message-ID: <20011228002434.A10135@melusine.cuivre.fr.eu.org> In-Reply-To: <p05101003b8510bd15ac4@[128.113.24.47]>; from drosih@rpi.edu on Thu, Dec 27, 2001 at 12:43:01PM -0500 References: <47197.1009447811@critter.freebsd.dk> <p05101003b8510bd15ac4@[128.113.24.47]>
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Le 2001-12-27, Garance A Drosihn écrivait :
> If I understand your request, you would want
> shutdown -p now
> to behave the same as
> shutdown -r now
> if the operating system does not know how to power down the hardware.
> Is that what you want?
Actually what I want would be more like support for a combination like:
shutdown -r -p now
(which is currently unsupported because we have assigned one signal
that says init 'shutdown -r' and another for 'shutdown -p', but that's
not the issue here.)
More precisely, right now if you do
reboot -p
then you have exactly the same behaviour as
halt -p
I.e. try to power down the system, and if the power down fails, then
halt.
What I would like to have is a means to try to powerdown the system,
and if the powerdown fails, then reboot. This comes in handy in the
following scenario:
1. UPS signals impending low battery condition;
2. UPS monitoring daemon starts shutdown;
3. kernel syncs buffers and umounts file systems;
4. using an ad hoc event handler registered in shutdown_final,
we then signal the UPS that it can stop outputting AC from
the battery backup (this is the powerdown action);
If the UPS is still on battery power at stage 4, then it will actually
power down the machine. On the other hand, if power was restored after
stage 2 (eg while the kernel was flushing its buffers), then the
signalling at stage 4 will have no effect and the machine needs to
reboot.
An alternative solution is to make a special-purpose binary that calls
shutdown(2) with RB_POWER set and RB_HALT cleared, or to use a different
method altogether for starting that emergency powerdown/reboot sequence.
On the other hand, it seems to me that RB_POWER should be the proper way
of requesting a powerdown action from the kernel.
Thomas.
--
Thomas.Quinot@Cuivre.FR.EU.ORG
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