Lately I needed to configure an Eaton 5L UPS for the P2C controller node. Power outages are becoming frequent nowadays. The main requirement is that when a power outage occurs, controller services (keystone, glance, nova, etc.) should be stopped and the node will shutdown, as well as the UPS. I am running Ubuntu 14.04 for the controller so NUT is easy to install (sudo apt-get install nut). It took me half a day to configure this, so to save you some time you can check out my config. Enjoy!