General information about ACPI.

Here, specify when the system should wake from a sleep state. Currently, this feature is not fully supported.

Provides information about possible sleep states.

All events are reported here and processed by a daemon like acpid or powersaved. If no daemon accesses this file, events, such as a brief click on the power button or closing the lid, can be read with cat /proc/acpi/event (terminate with Ctrl + C).

These files contain the ACPI tables DSDT (differentiated system description table) and FADT (fixed ACPI description table). They can be read with acpidmp, acpidisasm, and dmdecode. These programs and their documentation are located in the package pmtools. For example, acpidmp DSDT | acpidisasm.

Shows whether the AC adapter is connected.

Detailed information about the battery state. The charge level is read by comparing the last full capacity from info with the remaining capacity from state. A more comfortable way to do this is to use one of the special programs described below (see Section 9.3.1.2. “ACPI Tools”). The charge level at which a battery event is triggered can be specified in alarm.

This directory contains information about various switches.

Shows if the fan is currently active. The fan can be activated and deactivated manually by writing 0 (on) or 3 (off) into this file. However, both the ACPI code in the kernel and the hardware (or the BIOS) overwrite this setting when it gets too warm.

Information about the energy saving options of the processor.

Information about the current processor state. An asterisk next to ‘C2’ indicates that the processor is idle. This is the most frequent state, as can be seen from the usage figure.

This interface is no longer used.

Enables further linear throttling of the processor. This interface is outdated. Its function has been taken over by the settings in /etc/sysconfig/powersave/common (see Section 9.5.2.3. “Adapting the Power Consumption”).

If the performance and the throttling are automatically controlled by a daemon, the maximum limits can be specified here. Some of the limits are determined by the system, some can be adjusted by the user. However, their function has been taken over by the settings in /etc/sysconfig/powersave/common (see Section 9.5.2.2. “User-Defined Battery States”).

A separate subdirectory exists for every thermal zone. A thermal zone is an area with similar thermal properties whose number and names are designated by the hardware manufacturer. However, many of the possibilities offered by ACPI are rarely implemented. Instead, the temperature control is handled conventionally by the BIOS. The operating system is not given much opportunity to intervene, as the life span of the hardware is at stake. Therefore, some of the following descriptions only have a theoretical value.

Current temperature of the thermal zone.

The state indicates if everything is “ok” or if ACPI applies “active” or “passive” cooling. In the case of ACPI-independent fan control, this state will always be “ok”.

Enables the selection of the passive (less performance, very economical) or active (full performance, uninterrupted fan noise) cooling method for full ACPI control.

Enables the determination of temperature limits for triggering specific actions like passive or active cooling, suspension (“hot”), or a shutdown (“critical”).

If the value in temperature is not updated automatically when the temperature changes, the polling mode can be toggled here. The command echo X > /proc/acpi/thermal_zone/*/polling_frequency causes the temperature to be queried every X seconds. Set X=0 to disable polling.