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

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

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.



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