Configuring email notification on UPS shutdown.

[SingularityOS]

Hi all,

I’m seeking assistance to configure Proxmox to send an email (or Telegram message, if possible) when the system shuts down due to a UPS-triggered shutdown.

Setup Overview:

• My Proxmox server is a NUT client of a Synology NAS, which is connected to the UPS.

• During a live power outage test, when the Synology shuts down, Proxmox follows shortly after. This works fine with the default NUT config.

Goal:

I want Proxmox to notify me when a UPS-triggered shutdown is initiated, and tell my UDM SE to shutdown.

Current Attempt:

I used ChatGPT to do this, but later realised its not quite what I want.
I’ve created a shutdown script at /usr/lib/systemd/system-shutdown/udm_shutdown.sh with the following content:

#!/bin/bash
# This script runs during system shutdown to power off the UDM SE and send an email notification.

# Define email parameters
EMAIL_SUBJECT="Proxmox Shutdown Initiated"
EMAIL_RECIPIENT="my_email@example.com"
EMAIL_BODY="Proxmox is initiating shutdown. A command to power off the UDM SE has been sent."

# Send an email notification
echo "${EMAIL_BODY}" | mail -s "${EMAIL_SUBJECT}" "${EMAIL_RECIPIENT}"

# Send shutdown command to UDM SE via SSH
sshpass -p "your_password_here" ssh -o StrictHostKeyChecking=no root@192.168.1.1 ubnt-systool poweroff

The script works for shutting down my UDM SE. However, the email notification doesn’t send.

I believe this script runs too late in the shutdown process — possibly after email services are already terminated? When watching the hardware physically, I only see the UDM SE start shutting down moments before the proxmox host machine cuts power.

Additionally, I realised this script runs for all shutdowns and not just NUT-triggered ones.

I’m still a novice with most things Linux and would appreciate any guidance to:

1. Ensure the email notification is sent before Proxmox shuts down, even if it means it sends it on ALL shutdowns, I can live with this. I can't have my UDM shutting down on all shutdowns though.

2. Make this notification specific to NUT-triggered shutdowns, if possible.

Perhaps I need to spin up a VM, or external machine to handle the shutting down of the UDM SE and sending the email notification?

Thank you in advance for your help!