Date: Sat, 07 Feb 1998 06:57:56 -0800 From: Mike Smith <mike@smith.net.au> To: John Fieber <jfieber@indiana.edu> Cc: Calin Andrian <calin@ibd.dbio.ro>, freebsd-hackers@FreeBSD.ORG Subject: Re: Powering off the system/UPS Message-ID: <199802071457.GAA00739@dingo.cdrom.com> In-Reply-To: Your message of "Fri, 06 Feb 1998 09:25:53 EST." <Pine.BSF.3.96.980206092018.9421F-100000@fallout.campusview.indiana.edu>
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> > Maybe I missed it in the thread, but why it is a Good Thing to > put UPS support in the kernel as opposed to a purely user mode > daemon that monitors the UPS and does the Right Thing, like > shutdown(8), when things get to a critical state? There are a couple of cases where this is important: - Many UPS systems have a command that says "power off, and don't come back until the line is OK". Regardless of the line state, they *will* power off first, which guarantees that you get a hard reset. Some, but *not*all* of these provide a delay in the command, but you can't tell how long a shutdown is going to take. If you leave off commanding the cycle until after shutdown, it doesn't matter. - Other UPS systems are stupid, and with those the correct course to take is to reboot, and wait early in the boot phase (well before filesystems are mounted) until the line power comes back. To do this, you need a driver. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\
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