KDE Power Management 101

While there are exceptions, power management is primarily the concern of laptop, netbook, and tablet users, and as the world becomes increasingly reliant on these mobile devices, getting good battery life and conserving energy are top priorities.

KDE’s power management is controlled by an application called PowerDevil. There are three ways to access and manage PowerDevil:

1.System Settings module
2.Plasma Battery Monitor widget
3.Krunner plugin

System Settings

The PowerDevil System Settings module is found under the “Advanced” tab in the “Advanced User Settings” section. Click on “Power Management” to start it.

There are three side tabs:

PowerDevil configuration

1. General Settings – Here you can configure global settings that will apply to all profiles, such as “lock screen on resume”. It also allows you to assign profiles to certain situations. For example, when your laptop or netbook is unplugged, the “Powersave” profile is assigned by default.

The last button sets notifications. For example, when the laptop is unplugged, a system tray notification will pop up.

The “Advanced Battery Settings” tab allows users to set custom battery power levels.

PowerDevil configuration settings

2. Edit Profiles – Each profile has a plethora of settings, allowing users full control over the system’s power management. Here are some key features:

Disable desktop effects, if active – This is commonly used for lower-power situations. KWin desktop effects will use more CPU and GPU power. By enabling this setting, KDE will temporarily disable effects until the power profile changes.

Action settings – Pressing the power button, closing the laptop lid, or pressing the suspend key all have actions assigned to them, and PowerDevil gives you the ability to change those actions or disable them completely.

Screen – Dimming or turning off the screen can save power and extend the life of the screen. In this tab, you can set the specific times for each state, as well as the default brightness level for the given profile.

CPU – With multi-core systems, you can disable one or more of the CPUs when a profile is activated. If you have CPU scaling enabled, you can also set the scaling policy to run the CPU at a slower speed when on battery power.

3. Capabilities – The capabilities tab is essentially an information center that provides you with valuable information about your mobile computer. It will tell you what power features and actions are enabled and available.

Plasma Widget

Plasma battery monitor widget

The batter monitor widget displays the percentage of battery power remaining and tells the user if the cord is plugged in or not. Left click on the battery icon to bring up a quick access panel. From there, you can change the brightness, power profile, enable suspend or hibernate, and access the previously-mentioned system settings module. Right clicking brings up configuration options for the module.

Krunner

Krunner is an advanced command and application launcher. With it, you can quickly access settings, enable power actions, or change the system state. You can access it by pressing Alt+F2 or right clicking on the desktop and clicking “Run Command”.

Screen Brightness: To change the brightness of the screen, type “Screen Brightness ##”, replacing ## with a percentage number. For example: Screen Brightness 65. If you type “screen brightness” with no number, it will give you general options like “dim screen by half” and “turn off screen”.

Power Profile: Simply type in “power profile”, and Krunner will give you a list of profile options.

Power Governor: If enabled, this allows you to set the CPU governor profile.

Suspend: Type “suspend” and then select “Suspend to Disk” or “Suspend to RAM”

Troubleshooting

Q. My suspend and/or brightness keys do not work
A. Make sure you have KHotkeys enabled in System Settings/Advanced/Service Manager. If it still does not work, you may need to consult your distribution’s documentation on hotkeys for your particular laptop.

Q. I have an Nvidia card, and the GPU does not run at full speed. Where do I configure that?
A. If you are using Nvidia’s proprietary drivers, configure it with nvidia-settings.

Q. Suspend does not work, works only once, or freezes/crashes the laptop.
A. Linux suspend support will vary depending on the device. Check your distribution’s help documentation or forums.

KDE PowerDevil makes power management easy and completely integrated with the KDE graphical interface. Because of this, users can create their own Krunner plugins or Plasma widgets to interact with it. As Linux becomes more popular, particularly on netbooks, PowerDevil should play an important role.