NetBSD Documentation: Power Management
Power Management for Laptops
Sensor data includes battery, temperature, fan speed, and AC adapter status readings, which are provided through ACPI on most modern laptops.
NetBSD's framework for sensors is envsys(4).
The command line tool provided with NetBSD for examining sensors is
envstat(8), but various software in pkgsrc can also
read from envsys, including
sysutils/xbattbar, and various
ACPI Suspend (a type of low power mode where most devices are inactive, but can be quickly resumed) is supported. NetBSD can suspend to RAM with the following command:
sysctl -w hw.acpi.sleep.state=3
The system will automatically resume when it is triggered by the hardware (e.g. by the power button being pressed, or by the lid being lifted).
Suspend events can be automatically triggered by powerd(8)
scripts. For example, you can add a suspend command to
/etc/powerd/scripts/lid_switch to suspend
when your laptop's lid is closed. Make sure powerd is enabled in
Reducing the CPU frequency is a common way to reduce power consumption when the system is less active. The current CPU frequency is also controlled via sysctl(8), e.g:
sysctl -a | grep freqmachdep.cpu.frequency.target = 2300 machdep.cpu.frequency.current = 2300 machdep.cpu.frequency.available = 2300 2200 2000 1900 1800 1700 1500 1400 1300 1100 1000 900 800 600 500
sysctl -w machdep.cpu.frequency.target=1800
sysutils/estd package in
pkgsrc provides a daemon that scales the CPU frequency automatically
in line with the current CPU load.
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