OpenClaw + NUT: Smart UPS Monitoring and Graceful Shutdown Automation

Power Goes Out. Then What?

Jeff Geerling’s “NUT on my Pi” post resonated with every homelabber. Uninterruptible Power Supplies keep things running during outages — but someone needs to decide when to shut down. That someone is now OpenClaw.

The Setup

UPS (CyberPower 1500VA)
    │ USB
    ▼
Pi 5 (NUT Server + OpenClaw)
    │ Network
    ├── Pi (k3s cluster)
    ├── Pi (NAS)
    └── Switch

Installing NUT

# On the Pi connected to UPS via USB
sudo apt install nut

# Configure NUT
sudo cat > /etc/nut/ups.conf << 'EOF'
[cyberpower]
  driver = usbhid-ups
  port = auto
  desc = "CyberPower CP1500AVRLCD"
EOF

# Start NUT
sudo systemctl enable nut-server
sudo systemctl start nut-server

# Test
upsc cyberpower@localhost

OpenClaw Monitors NUT

Every heartbeat cycle, OpenClaw checks the UPS:

# Quick UPS status check
upsc cyberpower@localhost battery.charge
upsc cyberpower@localhost ups.status
upsc cyberpower@localhost battery.runtime

The Intelligence Layer

Here’s where OpenClaw beats a simple NUT script. Instead of “battery below 20% → shutdown everything,” OpenClaw makes smart decisions:

Scenario 1: Brief Outage

Power out. Battery: 95%. Runtime: 45 minutes.
→ OpenClaw: "Power outage detected. Battery at 95% (45 min runtime). 
   Monitoring. No action needed yet."
→ Waits quietly.
→ Power returns after 3 minutes.
→ OpenClaw: "Power restored. Total outage: 3 minutes. Battery at 92%."

Scenario 2: Extended Outage

Power out. Battery: 60%. Runtime: 25 minutes.
→ OpenClaw: "⚠️ Power out for 15 minutes. Battery at 60%.
   Plan: At 30% I'll shut down the NAS (save data).
   At 20% I'll shut down k3s workers.
   At 10% I'll shut down everything except myself."

Scenario 3: Critical

Battery: 15%. Runtime: 6 minutes.
→ OpenClaw: "🔴 CRITICAL: Battery at 15%. Initiating shutdown sequence."
   1. SSH to NAS: "sudo zpool export tank && sudo shutdown -h now" ✅
   2. SSH to k3s nodes: "kubectl drain && sudo shutdown -h now" ✅
   3. "All nodes shut down safely. I'll power off at 5%."
   4. Final message: "Going dark. Everything shut down clean. 
      I'll restart when power returns."

The Shutdown Script

#!/bin/bash
# /home/pi/graceful-shutdown.sh
# Called by OpenClaw when battery critical

echo "Phase 1: Stopping services"
ssh pi-nas "sudo systemctl stop jellyfin && sudo zpool export tank && sudo shutdown -h now"

echo "Phase 2: Draining k3s"
ssh pi-k3s-1 "kubectl drain pi-k3s-2 --ignore-daemonsets --force"
ssh pi-k3s-2 "sudo shutdown -h now"
ssh pi-k3s-1 "sudo shutdown -h now"

echo "Phase 3: Self-shutdown at 5%"
# OpenClaw will call: sudo shutdown -h now

Power-On Recovery

When power returns, the Pi (set to boot on power restore in BIOS/firmware) starts up, OpenClaw comes online, and:

1. Checks which nodes are back
2. Waits for NAS to boot and import ZFS pool
3. Verifies k3s cluster health
4. Sends recovery report:

✅ Power Restored — Recovery Complete Outage duration: 1 hour 23 minutes All 4 nodes back online ZFS pool: ONLINE, no errors k3s: 23/23 pods running UPS: Charging (currently 34%)

UPS Sizing

For my 30W homelab:

CyberPower 1500VA / 900W
Actual load: 30W
Runtime at 30W: ~2+ hours
Cost: $150

That's 2+ hours of grace period. More than enough for most outages.

The UPS doesn’t just keep things running — combined with OpenClaw, it orchestrates a clean shutdown and recovery. No data loss, no ZFS corruption, no orphaned pods.