| .TH POWERD 8 "Feb 14, 1994" "" "Linux System Administrator's Manual" |
| .SH NAME |
| .\" powerd \(em monitor a serial line connected to an UPS. |
| powerd -- monitor a serial line connected to an UPS. |
| .SH SYNOPSIS |
| .B /sbin/powerd |
| .RB " serial-device " |
| .SH DESCRIPTION |
| .B Powerd |
| is a daemon process that sits in the background and monitors the state |
| of the DCD line of the serial device. This line is meant to be |
| connected to a UPS (Uninterruptible Power Supply) so that \fBpowerd\fP knows |
| about the state of the UPS. As soon as \fBpowerd\fP senses that the |
| power is failing (it sees that DCD goes low) it notifies \fBinit\fP(8), |
| and \fBinit\fP then executes the \fBpowerwait\fP and \fBpowerfail\fP entries. |
| If \fBpowerd\fP senses that the power has been restored, it notifies \fBinit\fP |
| again and \fBinit\fP will execute the \fBpowerokwait\fP entries. |
| .SH ARGUMENTS |
| .IP serial-device |
| Some serial port that is not being used by some other device, and does not |
| share an interrupt with any other serial port. |
| .SH DIAGNOSTICS |
| \fBPowerd\fP regularly checks the \fBDSR\fP line to see if it's high. |
| \fBDSR\fP should be directly connected to \fBDTR\fP and \fBpowerd\fP |
| keeps that line high, so if \fBDSR\fP is low then something is wrong |
| with the connection. \fBPowerd\fP will notify you about this fact every |
| two minutes. When it sees that the connection has been restored it |
| will say so. |
| .SH HOWTO |
| It's pretty simple to connect your UPS to the Linux machine. The steps |
| are easy: |
| .TP 0.5i |
| .B 1. |
| Make sure you have an UPS with a simple relay output: it should |
| close its connections (make) if the power is gone, and it should |
| open its connections (break) if the power is good. |
| .TP 0.5i |
| .B 2. |
| Buy a serial plug. Connect the DTR line to the DSR line directly. |
| Connect the DTR line and the DCD line with a \fB10 kilo ohm\fP |
| resistor. Now connect the relay output of the UPS to GROUND |
| and the DCD line. If you don't know what pins DSR, DTR, DCD and |
| GROUND are you can always ask at the store where you bought the plug. |
| .TP 0.5i |
| .B 3. |
| You're all set. |
| .SH BUGS |
| Well, not a real bug but \fBpowerd\fP should be able to do a broadcast or |
| something on the ethernet in case more Linux-boxes are connected to |
| the same UPS and only one of them is connected to the UPS status line. |
| .SH SEE ALSO |
| .BR shutdown (8), |
| .BR init (8), |
| .BR inittab (5) |
| .SH AUTHOR |
| Miquel van Smoorenburg, miquels@cistron.nl |