powerd − UPS monitoring daemon


/sbin/powerd [tty]


powerd monitors the serial port connected to an UPS device and will perform an unattended shutdown of the system if the UPS is on battery longer than a specified number of minutes. powerd needs to watch a tty with modem control properties. Please refer to the powerd documentation for further information.
also has the capabilities of notifying other clients on the network that may have a UPS but not be connected to the serial line that there is a power outage, and id configured through the powerd.conf file


Here is the configuration format:
Lines beginning with ’#’ are ignored.
MODE <mode>

specifies the mode the UPS should be in. Valid arguements are MONITOR and PEER MONITOR being the mode to actually watch a UPS serial port, and PEER being to listen for a connection from a machine in MONITOR mode

MONITOR <device>

Specifies which device to monitor while in MONITOR mode. Specify an actual device file. Example: /dev/ttyS0

POWERFAIL <line> <high|low>

Specifies which lines on the serial ports indicate that the power is out. Valid arguements are DCD, CAR, CTS, and RNG. Also specify if the line being HIGH or LOW indicates a power failure.
Since most people may not know this arguement, Please use the enclosed upsdetect program to automatically find this line.

NOTIFY <hostname[:port]> <password>

Specified in MONITOR mode to notify a client running in PEER mode. Specify the hostname of the machine, and optional port the daemon is running on, And the password as specified by their LISTEN command. See below for more details.

LISTEN <hostname> <password>

Specified in PEER mode, specifies a hostname that is allowed to notify us of when the power is out, and the password they shall give us to authenticate themselves. The 2 passwords should match on the MONITOR mode machines NOTIFY password, and the PEER modes LISTEN password.


Specified in PEER mode, specifies the port that powerd should listen on. If you use this arguement, powerd shall not default to using port 532, and the machine in MONITOR mode must specify the port you use in their NOTIFY command.

DELAY <delayinseconds>

Specifies how many seconds before notifying init of a power outage. Note that this doesnt mean that the system will shut down in that many seconds, as it depends on how init is configured. Init usually issues a 2 min shutdown.

USER <username>

Specifies which username to drop to from root. The program will reobtain root access only when it needs to, Like when notifying init that the power is out. This is simply a security feature, and not needed for powerd to operate. Note: powerd must still be run initially as root. It will then drop to the user if, and only if, a username is specified.


None: Please use the configuration file /etc/powerd.conf which can be generated with detectups. See detectups(8) for more information



powerd configuration file


indicates line power status


init is what actually issues the



powerd(8), shutdown(8), wall(1), init(8), inittab(5).


James Brents <James@nistix.com> (with parts of this man page borrowed from all over the Linux community)

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