How to fix broken power management in Xubuntu 15.10 (16.04)

As we know Ubuntu has switched to the new "shiny" init system called systemd since the release 15.04. But the integration of that new init system isn't yet completely finished because some things aren't working as before the switch. Power management that utilized pm-utils previously is completely broken for example and no alternative solution is offered. In this article I'll explain how to restore pm-utils's old behaviour as a temporary workaround that can be used until a new and of course better official solution will be implemented.

Improving pm-utils power management scripts for pci devices

By default pm-utils changes power control parameters only for a subset of device classes. The classes id's are hardcoded into the /usr/lib/pm-utils/power.d/pci_devices script. Unfortunately it is not possible for a user to define his own set of classes to be treated by the script.