Controlling Your Desktop’s Power Management

GNOME Power Manager is a session daemon for the GNOME desktop that manages the power settings for your laptop or desktop computer. When running on battery, the GNOME Power Manager displays a battery icon showing the battery state in the panel. When hovering the mouse over the icon, a pop-up with more information is shown. To view detailed information about the batteries current state, left-click the icon and choose Laptop Battery. On certain events, such as a critically low battery state, the GNOME Power Manager will display notifications informing you about the event.

GNOME Power Manager is usually started automatically when GNOME starts, but you can manually start GNOME Power Manager by using the following command:

gnome-power-manager --verbose --no-daemon

Viewing Power Statistics

The statistics program lets you view the power consumption of your laptop hardware in graphic form. To access the statistics graphs, right-click the battery icon and choose Power History, or click Computer+More Applications+System+Power Statistics.

The Power History graph shows the power history charge used by the composite primary battery. The line represents the amount of power that is either being used to charge the batteries in the system or the power being used by the system from the batteries. You should see the line go up when processor intensive tasks are performed, and go down when the system is at idle (or when the screen is dimmed). A legend is shown with this graph when data events have been received.

You will not receive rate data from your computer if it is not charging or discharging, or if the computer is suspended. This is due to hardware limitations (where the rate is only sent from the battery management chip, rather than the power management chip on the motherboard).

Depending on your hardware, other graphs will be available from the Graph Type menu. You might also see additional hardware that can be accessed via the optional Devices button.

Modifying Power Management Preferences

The Power Management Preferences dialog box lets you control the LCD brightness when your system is on AC or battery power, the idle time for the screen power-down and suspend action, the actions to perform when the laptop lid is closed and the notification area icon policy.

To access Power Management Preferences, right-click the battery icon and choose Preferences, or click Computer+More Applications+System+Power Management.

On AC Power Preferences

Use the options on the On AC Power dialog box to automatically put your computer to sleep when it has been inactive for a specified amount of time. When your computer is asleep, it is turned on but in a low power mode (suspend to RAM). It takes less time for a computer to wake up from sleep than it does for the computer to start up after being turned off.

You can also set only the display to sleep and adjust the display brightness. If your computer is in the middle of a task (for example, burning a DVD) that you want to finish while you are away, set only the display to sleep.

Figure 2.5. GNOME Power Manager On AC Power Preferences

GNOME Power Manager On AC Power Preferences

On Battery Power Preferences

Use the options on the On Batter Power dialog box to automatically put your computer to sleep when it has been inactive for a specified amount of time, to specify what happens when the laptop lid is closed, and what happens when battery power is critically low.

When your computer is asleep, it is turned on but in a low power mode (suspend to RAM). It takes less time for a computer to wake up from sleep than it does for the computer to start up after being turned off.

You can also set only the display to sleep. If your computer is in the middle of a task (for example, burning a DVD) that you want to finish while you are away, set only the display to sleep.

Figure 2.6. GNOME Power Manager On Battery Power Preferences

GNOME Power Manager On Battery Power Preferences

General Preferences

Use the options on the General Power Management Preference dialog box to configure miscellaneous options related to GNOME Power Manager’s behavior, such as the actions to perform when the power or suspend buttons are pressed, if an icon is displayed in the Notification area and if sound is used to notify you in the event on an error.

Figure 2.7. GNOME Power Manager General Preferences

GNOME Power Manager General Preferences

Session and System Idle Times

gnome-screensaver is a session daemon that monitors user input (if the mouse has or has not been moved and if the keyboard has or has not been pressed) then starts a timeout. When the value of this timeout reaches the value set in Screensaver Preferences (using the Regard the computer as idle after option), then the login is marked as session idle.

As soon as the session is marked idle, GNOME Power Manager starts it's own system timer. When the timeout set in GNOME Power Manager Preferences is reached, and the CPU load is idle, then the idle action is performed (such as turning off the screen, suspending or hibernating the computer).

To make this clearer, the sliders in GNOME Power Manager Preferences are set to start at the value of the session-timeout + 1 minute, as GNOME Power Manager Preferences cannot logically trigger before the session is marked as idle. If you adjust the value of the session idle timeout in Screensaver Preferences, the start time of the sliders in GNOME Power Manager Preferences will change accordingly.

Figure 2.8. Changing the Session Idle Timeout in Screensaver Preferences

Changing the Session Idle Timeout in Screensaver Preferences

To access the screen saver preferences, click Computer+More Applications+Utilities+Screensaver. For more information, see Section 3.3.4, “Configuring the Screen Saver”.