Datasheet

“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 363 — #389
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17
Power Management
17.3.1 ACPI in Action
If the kernel detects an ACPI BIOS when the system is booted, ACPI is
activated automatically (and APM is deactivated). The boot parameter
acpi=on may be necessary for some older machines. The computer must
support ACPI 2.0 or later. Check the kernel boot messages in /var/log/
boot.msg to see if ACPI was activated. If this is the case, there is a direc-
tory /proc/acpi/, which is described later.
Subsequently, a number of modules must be loaded. This is done by the
start script of the ACPI daemon. If any of these modules causes prob-
lems, the respective module can be excluded from loading or unloading in
/etc/sysconfig/powersave/common. The system log (/var/log/
messages) contains the messages of the modules, enabling you to see
which components were detected.
In /proc/acpi/, find a number of files that provide information about the
system state or can be used to change some of the states actively. However,
many features do not work yet, either because they are still under develop-
ment or because they have not been implemented by the manufacturer.
All files (except dsdt and fadt) can be read with cat. In some files, set-
tings can be modified by entering echo X <file> to specify suitable val-
ues for X (the objects in /proc are not real files on the hard disks but inter-
faces to the kernel). The most important files are described below:
/proc/acpi/info General information about ACPI.
/proc/acpi/alarm Here, specify when the system should wake from a
sleep state. Currently, this feature is not fully supported.
/proc/acpi/sleep Provides information about possible sleep states.
/proc/acpi/event 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
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/proc/acpi/dsdt and /proc/acpi/fadt
These files contain the ACPI tables DSDT (differentiated system de-
scription 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.
363SUSE LINUX Enterprise Server