PebbleRack

Guide 21 of 25 · intermediate

Protect a lab with a UPS and graceful shutdown

Match load to a UPS, monitor its state, and rehearse a controlled shutdown.

Source-verified · Not lab-testedOfficial sources checked 2026-09-29. No PebbleRack hardware compatibility claim.

Outcome

You will have a documented power-failure plan, a monitored UPS state, and a safe shutdown sequence that you have rehearsed without pulling power from production equipment. A UPS buys time; it is not an indefinite power source or a substitute for backups. Exact runtime and shutdown timing depend on your actual UPS, load, battery condition, and software. PebbleRack has not tested or selected a compatible UPS for its planned products.

Before you start

Inventory the devices that must stay alive long enough to shut down: host, storage, network switch, and router if they are needed to send alerts. Measure or obtain actual power draw and inrush information; size the UPS using the manufacturer's published runtime curve with margin. Confirm electrical outlet and UPS ratings and follow the vendor's instructions. Choose a supported communication method, often USB or network, and check the Network UPS Tools (NUT) compatibility list for the exact model. Keep a local console path.

Steps

  1. Write the shutdown dependency order before connecting anything. Applications and guest workloads should stop cleanly before the host; network equipment may need to remain up until monitoring and storage have finished. Note which storage arrays require their own shutdown and whether a virtualized UPS monitor would disappear before the host. Prefer a monitor running on the system that can actually initiate host shutdown.
  2. Place the UPS where it can ventilate, connect only the loads in the capacity plan, and charge/test it per manufacturer guidance. Label battery-backed and surge-only outlets. Record model, serial number privately, battery age, warranty, and replacement date. Do not connect laser printers or other high-draw equipment to battery outlets unless explicitly supported.
  3. Install a supported NUT package for your OS and follow its current user manual to configure a driver for the exact UPS. Start in read-only observation: use upsc UPS_NAME@localhost or your configured host to read input status, battery charge, and runtime. Confirm values change sensibly when the UPS self-test runs. A recognized USB device alone is not proof that shutdown control works.
  4. Configure upsmon for a planned low-battery or forced-shutdown signal. Use a dedicated local monitor account and least-privilege credentials. Ensure the shutdown command targets the intended host. For a Proxmox node, review guest start/shutdown order and shutdown timeouts in the current administration guide. Never copy a generic threshold without comparing it to the observed time needed for your guests and host to shut down.
  5. Configure an alert for power-on-battery and low-battery events, ideally delivered through a path that remains powered. Document what happens if the network fails first. Alert delivery is secondary to a local automatic safe shutdown once battery charge reaches the danger threshold.
  6. Rehearse non-destructively: review the NUT status, stop a disposable guest normally, time its shutdown, and inspect the host's configured shutdown order. If safe under the UPS vendor's instructions, perform a controlled unplug-the-UPS-from-wall test with noncritical loads only and a local operator present. Never test on the only live data copy or during an active backup.

Check it worked

The UPS status is visible and plausible, the intended host has a shutdown trigger, the guest order is documented, and measured shutdown time fits within conservative battery time. An event produces a useful alert. A full outage response remains unverified until safely tested on the actual configuration.

If it fails / rollback

If NUT does not recognize the UPS, confirm exact model support, cable, driver, permissions, and service logs. If the shutdown plan is uncertain, leave automatic shutdown disabled while you fix it; retain local console access and the vendor's manual procedure. Reverse only new NUT service settings and restore the previous power wiring with the host already stopped if needed.

Safety and data notes

Power work can injure people or damage equipment. Follow the UPS manufacturer's electrical and battery safety instructions; do not open a UPS enclosure. Never simulate battery exhaustion on production to “prove” a guide. Battery runtime estimates are approximations and change with age and load.

Sources

Official sources checked 2026-09-29: NUT documentation; NUT manual pages; Proxmox VE administration guide.

Next guide

Continue with the incident runbook.