powerd

NAME

       powerd -- monitor a serial line connected to an UPS.

SYNOPSIS

       /sbin/powerd  serial-device

DESCRIPTION

       Powerd is a daemon process that sits in the background and
       monitors the state of the DCD line of the  serial  device.
       It  is  meant that this line is connected to an UPS (Unin-
       terruptible Power Supply) so that it knows about the state
       of  the  UPS.  As  soon as powerd senses that the power is
       failing (it sees that DCD goes low)  it  notifies  init(8)
       and init will execute the powerwait and powerfail entries.
       If powerd senses that the  power  has  been  restored,  it
       notifies  init again and init will execute the powerokwait
       entries.

ARGUMENTS

       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.

DIAGNOSTICS

       Powerd regulary checks the DSR line to see if  it's  high.
       DSR  should  be directly connected to DTR and powerd keeps
       that line high, so if DSR is low then something  is  wrong
       with  the  connection.  Powerd  will notify you about this
       fact every two minutes. When it sees that  the  connection
       has been restored it will say so.

HOWTO

       It's  pretty  simple  to  connect  your  UPS  to the Linux
       machine. The steps are easy:

       1.   Make sure you have an UPS with a simple  relais  out-
            put:  it  should  close its connections (make) if the
            power is gone, and it  should  open  its  connections
            (break) if the power is good.

       2.   Buy  a  serial  plug. Connect the DTR line to the DSR
            line directly.  Connect the DTR line and the DCD line
            with  a 10 kilo ohm resistor. Now connect the relais-
            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.

       3.   You're all set.

BUGS

       Well,  not  a  real  bug but powerd 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.

SEE ALSO

       shutdown(8), init(8), inittab(5).

AUTHOR

       Miquel van Smoorenburg, miquels@drinkel.ow.org