27.6 The YaST Power Management Module

The YaST power management module can configure all power management settings already described. When started from the YaST Control Center with System Power Management , the first dialog of the module opens (see Figure 27-1).

In this dialog, select the schemes to use for battery operation and AC operation. To add or modify the schemes, click Edit Schemes, which opens an overview of the existing schemes like that shown in Figure 27-2.

In the scheme overview, select the scheme to modify then click Edit. To create a new scheme, click Add. The dialog that opens is the same in both cases and is shown in Figure 27-3.

First, enter a suitable name and description for the new or edited scheme. Determine if and how the CPU performance should be controlled for this scheme. Decide if and to what extent frequency scaling and throttling should be used and whether processes with low priority (niced processes) should be ignored when adjusting the CPU frequency. In the following dialog for the hard disk, define a Standby Policy for maximum performance or for energy saving. The Acoustic Policy controls the noise level of the hard disk (supported by few hard disks). The Cooling Policy determines the cooling method to use. Unfortunately, this type of thermal control is rarely supported by the BIOS. Read /usr/share/doc/packages/powersave/powersave_manual.html#Thermal to learn how you can use the fan and passive cooling methods.

Global power management settings can also be made from the initial dialog using Battery Warning, ACPI Settings, or Suspend Permissions. Access these controls by clicking Other Settings and selecting the appropriate item from the menu. Click Battery Warning to access the dialog for the battery charge level, shown in Figure 27-4.

The BIOS of your system notifies the operating system whenever the charge level drops under certain configurable limits. In this dialog, define three limits: Warning Capacity, Low Capacity, and Critical Capacity. Specific actions are triggered when the charge level drops under these limits. Usually, the first two states merely trigger a notification to the user. The third critical level triggers a shutdown, because the remaining energy is not sufficient for continued system operation. Select suitable charge levels and the desired actions then click OK to return to the start dialog.

Access the dialog for configuring the ACPI buttons using ACPI Settings. It is shown in Figure 27-5. The settings for the ACPI buttons determine how the system should respond to certain switches. Configure the system response to pressing the power button, pressing the sleep button, and closing the laptop lid. Click OK to complete the configuration and return to the start dialog.

Click Enable Suspend to enter a dialog in which to determine if and how users of this system may use the suspend or standby functionality. Click OK to return to the main dialog. Click OK again to exit the module and confirm your power management settings.