Power Management

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man 4 acpi

hw.acpi.acline AC line state (1 means online, 0 means on battery power).

hw.acpi.lid_switch_state Suspend state (S1-S5) to enter when the lid switch (i.e., a note- book screen) is closed. Default is ``NONE (do nothing).


Suspend state (S1-S5) to enter when the power button is pressed. Default is S5 (power-off nicely).

hw.acpi.s4bios Indicate whether the system supports S4BIOS. This means that the BIOS can handle all the functions of suspending the system to disk. Otherwise, the OS is responsible for suspending to disk (S4OS). Most current systems do not support S4BIOS.

hw.acpi.sleep_button_state Suspend state (S1-S5) to enter when the sleep button is pressed. This is usually a special function button on the keyboard. Default is S3 (suspend-to-RAM).


Wait this number of seconds between preparing the system to sus- pend and actually entering the suspend state. Default is 1 sec- ond.


Suspend states (S1-S5) supported by the BIOS.

S1 Quick suspend to RAM. The CPU enters a lower power state, but most peripherals are left running.

S2 Lower power state than S1, but with the same basic char- acteristics. Not supported by many systems.

S3 Suspend to RAM. Most devices are powered off, and the system stops running except for memory refresh.

S4 Suspend to disk. All devices are powered off, and the system stops running. When resuming, the system starts as if from a cold power on. Not yet supported by FreeBSD unless S4BIOS is available.

S5 System shuts down cleanly and powers off.


hw.acpi.reset_video Enables calling the VESA reset BIOS vector on the resume path. This can fix some graphics cards that have problems such as LCD white-out after resume. Default is 0 (disabled).

man 4 powerd

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