UWMLSC > Beowulf Systems > Medusa

Network UPS Tools (NUT)

How It Works

NUTs Init Script

  • /etc/init.d/nuts starts 3 programs
    1. /usr/sbin/tripplite (or other UPS driver name)
    2. /usr/sbin/upsd
    3. /usr/sbin/upsmon
  • NOTE: Whether or not UPSD gets started is determined by /etc/sysconfig/ups.
  • This will determine if the machine will be a UPS server or client based on its IP address.


  • UPSD is the server software that runs on s001, s021, s041....
  • It will look at /etc/ups/upsd.conf for access information.


  • This is the driver that allows communication between UPSD and the UPS.
  • It will look at /etc/ups/ups.conf for driver information.


  • This is the program that queries UPSD as to the status of the UPS.
  • UPSMON runs on all machines running NUTs.
  • The prorgram looks to /etc/ups/upsmon.conf for config info.
  • NOTE: Changes should be made to /etc/ups/upsmon.conf.base as this file generates the upsmon.conf file.

    UPSSCHED Script

  • Upon power loss, the ON BATTERY status will cause upssched.sh to run.
  • This will begin a countdown to when the machine will shutdown.
  • Changes should be made to /etc/ups/upssched.conf

    How NUTs Works On Cluster Nodes s001 Through s296
    How NUTs Works On The Servers
    How To Install NUTs On A GC Machine

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