Many thanks to those that responded to my original posting with information about Network UPS Tools and commercial UPS products. In our planning a path forward to implement UPS-based power fail protection, we have come across what appears to be an issue with the state of the CentOS 6 machines being UPS protected. Most of these machines are desktop/deskside machines that are likely to be idle during non-work hours. It is also likely that they will be hibernating or in a power save mode. In the power save mode, these machines do not respond to keyboard or mouse activity. They also do not respond to network traffic such as a ping from other systems on the network. The method we use to wake them up is a quick push on the power button when the hibernation state is indicated by the button's yellow LED display. This state of hibernation leaves us wondering if these systems will be able to respond to network messages sent by the UPS. We have not yet made it all the way through the NUT and UPS documentation. The hibernation answer may very well be therein, but we have not found it so far. Any help or direction regarding the hibernation issue as it relates to UPS power fail protection will be appreciated. Thanks again and best regards.