Mike Smith wrote:
>
> The canonical way to do this is actually to shudown and reboot.
>
> In the _startup_ phase, while the root filesystem is still mounted
> readonly, you check the UPS status. At this point, you have access to
> the disk in a read-only fashion, and you can power-off (or have the UPS
> die) at any time.
By the way, for anyone interested, one way to achieve this if your UPS
is too
dumb to provide a "power good" signal is to take a 12vdc wall-wart and
plug
it into an _unprotected_ outlet. Connect this to a serial port, + to
ground,
- to DCD. Presto - that port's DCD signal now is a wall-power-good
signal.
You might optionally put a 1k resistor across the two pins to make sure
that
any filter caps bleed quickly off (a 12 ma load at 12 volts).
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