A LAN-connected watchdog using an ESP32 that safely shuts down your NAS or server when power is lost — like a literal canary in a server mine.

My Zimacube Pro server (MU/TH/UR) runs on a basic UPS without NUT or similar connectivity. I wanted a reliable, local-only way to detect when the power goes out — and shut things down cleanly before ZFS could cry.

Enter: Dead Canary
An ESP32 sits on the same power strip as the NAS (but not on the UPS), and serves a local / endpoint returning "CHIRP". When that chirp goes silent, the NAS knows it’s time to go dark.

• ESP32 development board
• Arduino IDE
• A Linux server or NAS
• Local Wi-Fi
• (Optional) Hipster film cannister for housing

• Connects to Wi-Fi
• Hosts a webserver on port 80
• Responds to http://CANARY_IP/ with "CHIRP"

• Cron job pings the canary every minute
• If no chirp in 5 minutes, triggers:

  shutdown -h now
  
  
  
  
  

• Update ssid and password with your Wi-Fi credentials
• Upload the sketch using Arduino IDE
• Use Serial Monitor to see the assigned IP

Place the script:

sudo nano /usr/local/bin/canary-watchdog.sh

Make it executable:

sudo chmod +x /usr/local/bin/canary-watchdog.sh

Add it to root’s crontab to run every minute:

sudo crontab -e

Then add this line:

* * * * * /usr/local/bin/canary-watchdog.sh >> /var/log/canary-watchdog.log 2>&1

To simulate power loss:

• Unplug the ESP32 or disconnect its Wi-Fi
• After 5 minutes of silence, the NAS will shut down
• (Optional) Replace shutdown -h now with a log echo to test safely

• I used Uptime Kuma to monitor the Canary IP.
• If the MU/TH/UR is still up but Kuma alerts me, I know the ESP has been unplugged (likely by Arnold the cat).

• ESP32 must not be powered by the UPS
• No cloud dependencies
• Local, autonomous, and extremely reliable