reduce the power consumption of a system when inactive

 PowerNap watches a series of configurable monitors. When no activity
 has occurred on any of these monitors for some specified time, PowerNap
 deems the system inactive, and takes action, as configured by the system
 administrator.
 .
 PowerNap can monitor:
   * User Activity (Console, Keyboard, Mouse)
   * System Activity (Load, Processes, Process IO)
   * Network Activity (wake-on-lan, UDP ports, TCP ports)
 .
 Some of these are event-based, while others are poll-based. PowerNap's
 polling interval, INTERVAL_SECONDS, is configurable.
 .
 The required length of inactivity, ABSENT_SECONDS, is configurable.
 .
 The action taken by PowerNap when the system is active, is configurable,
 and might be one of pm-powersave, pm-suspend, pm-hibernate, poweroff,
 or any executable script as chosen by the system administrator.
 .
 See /etc/powernap/config for all configurable options and defaults.