74 lines
3.1 KiB
Groff
74 lines
3.1 KiB
Groff
'\" -*- coding: UTF-8 -*-
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.\" Copyright (C) 1994 Miquel van Smoorenburg.
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.\"
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" the Free Software Foundation; either version 2 of the License, or
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.\" (at your option) any later version.
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.\"
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.\" This program is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program; if not, write to the Free Software
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.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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.\"
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.TH POWERD 8 "Feb 14, 1994" "" "Linux System Administrator's Manual"
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.SH NAME
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.\" powerd \(em monitor a serial line connected to an UPS.
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powerd -- monitor a serial line connected to an UPS.
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.SH SYNOPSIS
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.B /sbin/powerd
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.RB " serial-device "
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.SH DESCRIPTION
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.B Powerd
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is a daemon process that sits in the background and monitors the state
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of the DCD line of the serial device. This line is meant to be
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connected to a UPS (Uninterruptible Power Supply) so that \fBpowerd\fP knows
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about the state of the UPS. As soon as \fBpowerd\fP senses that the
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power is failing (it sees that DCD goes low) it notifies \fBinit\fP(8),
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and \fBinit\fP then executes the \fBpowerwait\fP and \fBpowerfail\fP entries.
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If \fBpowerd\fP senses that the power has been restored, it notifies \fBinit\fP
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again and \fBinit\fP will execute the \fBpowerokwait\fP entries.
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.SH ARGUMENTS
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.IP serial-device
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Some serial port that is not being used by some other device, and does not
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share an interrupt with any other serial port.
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.SH DIAGNOSTICS
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\fBPowerd\fP regularly checks the \fBDSR\fP line to see if it's high.
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\fBDSR\fP should be directly connected to \fBDTR\fP and \fBpowerd\fP
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keeps that line high, so if \fBDSR\fP is low then something is wrong
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with the connection. \fBPowerd\fP will notify you about this fact every
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two minutes. When it sees that the connection has been restored it
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will say so.
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.SH HOWTO
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It's pretty simple to connect your UPS to the Linux machine. The steps
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are easy:
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.TP 0.5i
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.B 1.
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Make sure you have an UPS with a simple relay output: it should
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close its connections (make) if the power is gone, and it should
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open its connections (break) if the power is good.
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.TP 0.5i
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.B 2.
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Buy a serial plug. Connect the DTR line to the DSR line directly.
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Connect the DTR line and the DCD line with a \fB10 kilo ohm\fP
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resistor. Now connect the relay output of the UPS to GROUND
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and the DCD line. If you don't know what pins DSR, DTR, DCD and
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GROUND are you can always ask at the store where you bought the plug.
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.TP 0.5i
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.B 3.
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You're all set.
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.SH BUGS
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Well, not a real bug but \fBpowerd\fP should be able to do a broadcast or
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something on the ethernet in case more Linux-boxes are connected to
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the same UPS and only one of them is connected to the UPS status line.
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.SH SEE ALSO
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.BR shutdown (8),
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.BR init (8),
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.BR inittab (5)
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.SH AUTHOR
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Miquel van Smoorenburg, miquels@cistron.nl
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