FreeBSD 7.0 manual page repository

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powerd - system power control utility



      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 con‐
      trol options accordingly.  It offers three modes (maximum, minimum, and
      adaptive) that can be individually selected while on AC power or batter‐
      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
      -p ival     Specifies a different polling interval (in milliseconds) for
                  AC line state and system idle levels.  The default is 500 ms.
      -P pidfile  Specifies an alternative file in which the process ID should
                  be stored.  The default is /var/run/
      -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.
      -v          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.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.