POWERD(8) MidnightBSD System Manager’s Manual POWERD(8)


powerd — system power control utility


powerd [−a mode] [−b mode] [−i percent] [−n mode] [−p ival] [−P pidfile] [−r percent] [−v]


The powerd utility monitors the system state and sets various power control options accordingly. It offers three modes (maximum, minimum, and adaptive) that can be individually selected while on AC power or batteries.

Maximum mode chooses the highest performance values. Minimum mode selects the lowest performance values to get the most power savings. Adaptive mode attempts to strike a balance by degrading performance when the system appears idle and increasing it when the system is busy. It offers a good balance between a small performance loss for greatly increased power savings. The default mode is adaptive.

The powerd utility recognizes the following runtime options:

−a mode

Selects the mode to use while on AC power.

−b mode

Selects the mode to use while on battery power.

−i percent

Specifies the CPU idle percent level when adaptive mode should begin to degrade performance to save power. The default is 90% or higher.

−n mode

Selects the mode to use normally when the AC line state is unknown.

−p ival

Specifies a different polling interval (in milliseconds) for AC line state and system idle levels. The default is 500 ms.


Specify an alternative file in which to store the process ID. The default is /var/run/powerd.pid.

−r percent

Specifies the CPU idle percent level where adaptive mode should consider the CPU running and increase performance. The default is 65% or lower.


Verbose mode. Messages about power changes will be printed to stdout and powerd will operate in the foreground.


acpi(4), apm(4), cpufreq(4)


The powerd utility first appeared in FreeBSD 6.0.


Colin Percival first wrote estctrl, the utility that powerd is based on. Nate Lawson then updated it for cpufreq(4), added features, and wrote this manual page.


The powerd utility should also power down idle disks and other components besides the CPU.

If powerd is used with power_profile, they may override each other.

The powerd utility should probably use the devctl(4) interface instead of polling for AC line state.

MidnightBSD 0.3 April 10, 2005 MidnightBSD 0.3