Advanced Power Management in Linux Operating System (2)

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Advanced Power Management in Linux Operating System (2) [Copy link]

1. Advanced Power Management

　　APM applications include: apmd (APM background service program) and other applications (such as APM). It is recommended to go to rpmfind.net to find the latest version suitable for your use. After installing and running OK, we can try the APM command.

　　The simplest use of APM is to display the battery capacity in the machine.

　　APM
　　AC on-line, no system battery

　　If APM is not supported, it will display "No APM support in kernel". At this time, first check whether there is /proc/apm. If not, check whether the kernel is running after APM is installed. If you have APM as a module, check whether the module is loaded. APM can also use -S/-s to enter standby and suspend state respectively.

Figure 1

　　Figure 1 is the KDE system interface, which uses APM to check battery capacity, manage other hardware energy saving modes (Figure 2), and display them in the taskbar. For more information, please visit www.linuxdoc.org .

　　2. ACPI

　　Linux has better support for ACPI and more related documentation than APM.

　　The authoritative website of ACPI is http://phobos.fs.tum.de/acpi/ , which includes two contents in the download column: acpid and pmtools, which can better optimize and manage ACPI.

Figure 2

　　There is a command in Pmtools called Pmtest that allows you to test devices. Basically, it shows the ACPI devices on your system and allows you to "suspend" or "standby" them. It must be run as root.

/pmtools/pmtest
VGA (D0)
keyboard (D0)
PCI 0×0 (D0)
system 0×0 (D0)

　　It seems that the VGA display, keyboard, PCI bus and system are all recognized as ACPI devices. Their state is D0, which is the active state. We can set the state to D1/D2 (minimize power consumption) or D3 (completely shut down). For example:

　　/pmtools/pmtest -d1 VGA

　　The monitor should now go black. This does not stop the graphics card from producing a video signal (the monitor will also indicate that there is an input signal), it just turns the signal all black. /pmtools/pmtest -d0 VGA should recover.

　　We have only given a few examples above. You can learn from them and manage your system well to give full play to the advanced voltage management functions.