Ubuntu Nut UPS (with Eaton 3s)

Nut / UPS




Status Values


  • OL - On line (no power failure) (opposite of OB - on battery)
  • LB - Low battery
  • SD - Shutdown load
  • CP - Cable power (must be present for cable to have valid reading)
  • CTS - Clear to Send. Received from the UPS.
  • RTS - Ready to Send. Sent by the PC.
  • DCD - Data Carrier Detect. Received from the UPS.
  • RNG - Ring indicate. Received from the UPS.
  • DTR - Data Terminal Ready. Sent by the PC.
  • ST - Send a BREAK on the transmit data line

A "-" in front of a signal name (like -RNG) means that the indicated condition is signaled with an active low signal. For example, [LB=-RNG] means the battery is low when the ring indicate line goes low, and that the battery is OK when that line is held high.


  • apt-get install nut

  • lsusb

    • 0463:ffff MGE UPS Systems UPS

  • vi /etc/default/nut

    • START_UPSD=yes
  • vi /etc/nut/ups.conf
    • https://networkupstools.org/docs/man/ups.conf.html
    • [eaton3s]
              desc="EATON UPS"
              # Power down the server at a higher battery charge level (40%) than default 20%
              # This should help with older, weaker batteries
              ignorelb = yes
              override.battery.charge.low = 40
      # !!! Comment out, invalid for Ubuntu 18.04:
      #maxretry = 3
  • vi /etc/nut/upsmon.conf
    • MONITOR eaton3s@localhost 1 monuser pass master
      SHUTDOWNCMD "/etc/nut/shutdown"
  • vi /etc/nut/nut.conf
    • MODE=standalone
  • vi /etc/nut/upsd.users
    • [monuser]
      upsmon master
      actions = SET
      instcmds = ALL
  • vi /etc/nut/shutdown
    • #!/bin/bash
      # UPS didn't shutdown, so we wrote this script
      upsdrvctl stop
      upsdrvctl shutdown
  • chmod 750 /etc/nut/shutdown
  • chown root:nut /etc/nut/shutdown
  • Reboot

Mute Beeper

  • upscmd -l eaton3s
  • upscmd eaton3s beeper.mute
    • username: monuser
    • password: pass

Test / Troubleshooting

  • Ubuntu 16.04 and older
    • service upsd status
    • service upsmon status
  • The commands above do not exist in Ubuntu 18.04. Instead?
    • service nut-driver status
    • service nut-server status
    • service nut-monitor status
  • lsusb
    • Bus 001 Device 004: ID 0463:ffff MGE UPS Systems UPS
  • upsc eaton3s
  • upsmon -c fsd
    • simulates a ups shutdown event, power down, upc cuts power, restarts

Problem: Nut Driver does not start


  • upsc eaton3s
  • service nut-server status
  • service nut-server restart

Try manual start and look for errors

  • /sbin/upsdrvctl start

This in turn executes

  • /lib/nut/usbhid-ups -a eaton3s


Problem: Nut Driver does not start up correctly on reboot

Old solution:

  • vi /etc/rc.local
    • #!/bin/sh -e
      # rc.local
      # This script is executed at the end of each multiuser runlevel.
      # Make sure that the script will "exit 0" on success or any other
      # value on error.
      # Sometime UPS driver does not start up correctly
      sleep 300
      service nut-driver restart
      exit 0

Still occasional problems, ups usb device not found

Try usb reset... (did not work)

  • lspci | grep XHCI | cut -d' ' -f1
    • 00:10.0
  • echo -n "0000:00:10.0" | tee /sys/bus/pci/drivers/xhci_hcd/unbind
  • echo -n "0000:00:10.0" | tee /sys/bus/pci/drivers/xhci_hcd/bind
  • lspci | grep EHCI | cut -d' ' -f1
    • 00:12.0

  • echo -n "0000:00:12.0" | tee /sys/bus/pci/drivers/ehci-pci/unbind

  • echo -n "0000:00:12.0" | tee /sys/bus/pci/drivers/ehci-pci/bind



  • service nut-driver restart;service nut-driver status
  • lsusb -v
    • Bus 001 Device 004: ID 0463:ffff MGE UPS Systems UPS
  • /lib/nut/usbhid-ups -a eaton3s -DDD
  • /lib/nut/usbhid-ups -a eaton3s -DDD -x explore -x vendorid=0x0463

Cron Job

Eaton 3s has regular driver connection problems. Some times it takes multiple tries to connect to the UPS.
This cronjob checks the USP connection every five minutes and restarts the driver if necessary.
If it still does not work, try another USB port, a USB 2.0 port if available and finally a (better?) USB cable.

  • vi /etc/cron.d/nutups
    • # check nut ups driver and force reload if failure
      */5 *     * * *     root  upsc eaton3s ups.status > /dev/null 2>&1; if [ $? != 0 ]; then echo "UPS driver connection failed, trying restart..." >&2; systemctl restart nut-driver; fi 
  • chmod 755 /etc/cron.d/nutups


Power off another server

Goal: the master server with the UPS connected, should shutdown other server(s), e.g. "server1" in case of low UPS battery state. All commands as user "root".

On master server with UPS connected via USB:

  • vi /etc/nut/shutdown.local
    • #!/bin/bash
      # For every target server add the following lines:
      # Pipe message to logger and stderr
      echo Shutting down server1, which is also using the master server UPS | tee /dev/stderr | logger
      ssh -p 2222 nutremote@server1.example.com sudo systemctl poweroff -i
  • cat ~/.ssh/id_rsa.pub
    • ssh-rsa AAAAB3NzaC1yc2EAAA...
    • Copy to clipboard/editor, we need this output later.

On server without UPS, e.g. "server1":

Server needs BIOS setting "Power on after power loss" to automatically turn on again after low battery shutdown!

  • adduser nutremote
  • adduser nutremote ssh-user
    • optional, this group may not exist on your system
  • passwd --lock nutremote
    • Disable password login
  • mkdir /home/nutremote/.ssh
  • vi /home/nutremote/.ssh/authorized_keys
    • restrict,command="sudo systemctl poweroff -i"
    • Paste master server public ssh key from above (~/.ssh/id_rsa.pub)
      The goal is a long single line of text separated by a space:
    • restrict,command="sudo systemctl poweroff -i" ssh-rsa AAAAB3NzaC1yc2EAAA...
  • chmod 600 /home/nutremote/.ssh/authorized_keys
  • chown -R nutremote:nutremote /home/nutremote
  • visudo
    • # Allow master server NUT UPS to power off this host
      nutremote ALL = NOPASSWD: /bin/systemctl poweroff -i

Testing the setup

On master server with UPS connected via USB:

  • /etc/nut/shutdown.local
    • The target server, e.g. "server1" should shut down.


Alternative Hardware

BlueWalker PowerWalker VI 600 SCL