Overview

Shutdown design

When your UPS batteries get low, the operating system needs to be brought down cleanly. Also, the UPS load should be turned off so that all devices that are attached to it are forcibly rebooted.

Here are the steps that occur when a critical power event happens:

1. The UPS goes on battery

2. The UPS reaches low battery (a "critical" UPS), that is to say upsc displays:

   ups.status: OB LB

   The exact behavior depends on the specific device, and is related to:

   • battery.charge and battery.charge.low
   • battery.runtime and battery.runtime.low

   
   

3. The upsmon master notices and sets "FSD" - the "forced shutdown" flag to tell all slave systems that it will soon power down the load.

   (If you have no slaves, skip to step 6)

4. upsmon slave systems see "FSD" and:

   • generate a NOTIFY_SHUTDOWN event
   • wait FINALDELAY seconds - typically 5
   • call their SHUTDOWNCMD
   • disconnect from upsd

   
   

5. The upsmon master system waits up to HOSTSYNC seconds (typically 15) for the slaves to disconnect from upsd. If any are connected after this time, upsmon stops waiting and proceeds with the shutdown process.

6. The upsmon master:

   • generates a NOTIFY_SHUTDOWN event
   • waits FINALDELAY seconds - typically 5
   • creates the POWERDOWNFLAG file - usually /etc/killpower
   • calls the SHUTDOWNCMD

   
   

7. On most systems, init takes over, kills your processes, syncs and unmounts some filesystems, and remounts some read-only.
8. init then runs your shutdown script. This checks for the POWERDOWNFLAG, finds it, and tells the UPS driver(s) to power off the load.
9. The system loses power.
10. Time passes. The power returns, and the UPS switches back on.
11. All systems reboot and go back to work.

...

• upsname = qnapups
• user = deepthought
• password = 123456

Setup Timer to Shutdown after 1 Minute

Edit the upssched.conf file

$ sudo vi /etc/nut/upssched.conf

Ensure that the CMDSCRIPT is set

CMDSCRIPT /bin/upssched-cmd

Add the following

# Timer to shutdown machine after 60 seconds
AT ONBATT * START-TIMER onbattwarn 60
AT ONLINE * CANCEL-TIMER onbattwarn

Edit the Command Script

$ sudo vi /bin/upssched-cmd

case $1 in
        onbattwarn)
                logger -t upssched-cmd "Timer On Battery Warning has been triggered - Shutting Down!"
                wall "Shutting down in 30 seconds!"
                shutdown -h `date --date "now + 30 seconds"`
                shutdown -h now
                ;;
        *)
                logger -t upssched-cmd "Unrecognized command: $1"
                ;;
esac

Restart Nut Client

Restart nut client:

...