ACPI

The Advanced Configuration and Power Interface (ACPI) [9] lets you intervene actively with the system's power management. Tools such as Acpitool [10] and Acpiclient [11] inhabit the ACPI framework. To reduce the power used by unnecessary interfaces and devices, you can turn to GUI power management tool for your desktop interface, or use a tool such as Hdparm or Sdparm for hard drives.

Mobile devices such as laptops benefit from tools in the laptop-mode-tools package [12]. A graphical interface lets users change many parameters with a single mouse click (Figure 4). For example, if you are not connected to a wireless network, simply disable the wireless chip (Enable modules wireless-ipw-power, wireless-iwl-power, or wireless-power) to easily save the power these components otherwise require. For information on the parameters, check out the laptop-mode-tools project documentation, as well as the wikis for Arch Linux [13] and Ubuntu [14]. And see the article on ACPI elsewhere in this issue.

Figure 4: The graphical interface of laptop-mode-tools.

Powertop [15] gives you details of the system load. The program comes with five views: Overview, Idle stats, Frequency stats, Device stats, and Tunables. You can press Tab or Shift+Tab to change tabs. The device statistics answer the question of which devices are consuming too much power: In addition to the battery discharge rate, Powertop shows the extent to which a device or interface is busy (Figure 5).

Figure 5: Powertop shows how much each component is being used.

Conclusions

Linux is not known for maximizing the theoretical maximum battery life of a mobile device, but current kernels and modern desktop environments with integrated power saving mechanisms have helped Linux narrow the gap with other systems. The Linux environment includes several useful tools you can use to configure the power configuration manually.

Keeping unneeded components and processes active costs energy without giving the user anything in return. You can find these power hogs with the current crop of tools and put your laptop on a battery diet.