c1c27e3b7e90e6fd0fc05f9f47ed11b3cb17dce5
[sysvinit.git] / obsolete / powerd.8
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2 .\" Copyright (C) 1994 Miquel van Smoorenburg.
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18 .TH POWERD 8 "Feb 14, 1994" "" "Linux System Administrator's Manual"
19 .SH NAME
20 .\" powerd \(em monitor a serial line connected to an UPS.
21 powerd -- monitor a serial line connected to an UPS.
22 .SH SYNOPSIS
23 .B /sbin/powerd
24 .RB " serial-device "
25 .SH DESCRIPTION
26 .B Powerd
27 is a daemon process that sits in the background and monitors the state
28 of the DCD line of the serial device. This line is meant to be
29 connected to a UPS (Uninterruptible Power Supply) so that \fBpowerd\fP knows
30 about the state of the UPS. As soon as \fBpowerd\fP senses that the
31 power is failing (it sees that DCD goes low) it notifies \fBinit\fP(8),
32 and \fBinit\fP then executes the \fBpowerwait\fP and \fBpowerfail\fP entries.
33 If \fBpowerd\fP senses that the power has been restored, it notifies \fBinit\fP
34 again and \fBinit\fP will execute the \fBpowerokwait\fP entries.
35 .SH ARGUMENTS
36 .IP serial-device
37 Some serial port that is not being used by some other device, and does not
38 share an interrupt with any other serial port.
39 .SH DIAGNOSTICS
40 \fBPowerd\fP regularly checks the \fBDSR\fP line to see if it's high.
41 \fBDSR\fP should be directly connected to \fBDTR\fP and \fBpowerd\fP
42 keeps that line high, so if \fBDSR\fP is low then something is wrong
43 with the connection. \fBPowerd\fP will notify you about this fact every
44 two minutes. When it sees that the connection has been restored it
45 will say so.
46 .SH HOWTO
47 It's pretty simple to connect your UPS to the Linux machine. The steps
48 are easy:
49 .TP 0.5i
50 .B 1.
51 Make sure you have an UPS with a simple relay output: it should
52 close its connections (make) if the power is gone, and it should
53 open its connections (break) if the power is good.
54 .TP 0.5i
55 .B 2.
56 Buy a serial plug. Connect the DTR line to the DSR line directly.
57 Connect the DTR line and the DCD line with a \fB10 kilo ohm\fP
58 resistor. Now connect the relay output of the UPS to GROUND
59 and the DCD line. If you don't know what pins DSR, DTR, DCD and
60 GROUND are you can always ask at the store where you bought the plug.
61 .TP 0.5i
62 .B 3.
63 You're all set.
64 .SH BUGS
65 Well, not a real bug but \fBpowerd\fP should be able to do a broadcast or
66 something on the ethernet in case more Linux-boxes are connected to
67 the same UPS and only one of them is connected to the UPS status line.
68 .SH SEE ALSO
69 .BR shutdown (8),
70 .BR init (8),
71 .BR inittab (5)
72 .SH AUTHOR
73 Miquel van Smoorenburg, miquels@cistron.nl