Date: Sat, 20 May 2000 17:53:10 -0700 From: Nick Sayer <nsayer@quack.kfu.com> To: Mike Smith <msmith@FreeBSD.ORG> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Post-shutdown hook for UPS shutdown? Message-ID: <39273376.529E92F7@quack.kfu.com> References: <200005191821.LAA09144@mass.cdrom.com>
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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). To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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