Power Out, Data Safe: UPS Sizing, NUT, Graceful Shutdown for Proxmox and TrueNAS, and Cutting Your Homelab’s Power Use

Power Out, Data Safe is a practical guide to protecting a Proxmox and TrueNAS homelab from power cuts, and to making it draw less power every ordinary day. It starts from the job a homelab UPS actually has: not keeping everything running through a long outage, but buying enough minutes for every machine to shut down cleanly, in the right order, and to come back on its own. You size the UPS from your own measured load and the vendor's published runtime chart, install Network UPS Tools on the Proxmox host as the one machine that talks to the UPS, and connect TrueNAS, Linux machines and Home Assistant as clients. Proxmox stops its guests in order with the guest agent and timeouts you measured, a timer forces the shutdown before the battery runs low, and the UPS power-cycles the load so everything boots again in order when the mains returns. Then you prove it: a status check from every machine, a forced shutdown with the mains still on, and a real plug-pull test, with the logs read afterwards and a battery calendar. The last part measures what the homelab draws at the wall and in the CPU, and cuts idle power without breaking anything, including the USB link to the UPS. Every version, option, default and menu path was checked against the official NUT, Proxmox VE, TrueNAS, Debian, Linux kernel and Home Assistant documentation in November 2026. No prices, no runtime or wattage claims about your hardware: you measure your own.

What you get

• Before We Start: what a power cut does to a homelab, the reference build (one UPS, NUT on the Proxmox host, everything else as a client) and the versions in this book
• What a UPS actually does: standby, line-interactive and online designs, VA versus watts and power factor, runtime as a chart rather than a number, sine-wave output, lead-acid and LiFePO4 batteries, and USB, serial or network-card communication
• Sizing the UPS to the job: what goes on battery, measuring the real load, how many minutes a clean shutdown needs, a sizing worksheet and plugging it in the right way
• NUT on the host: installing NUT on Proxmox VE / Debian 13, nut-scanner, ups.conf with usbhid-ups, nut.conf, upsd.conf, upsd.users, upsmon.conf as primary, file permissions, upsc and upscmd
• Clients and shutdown order: how a NUT shutdown runs (FSD, HOSTSYNC, FINALDELAY), a Debian secondary, TrueNAS's UPS service as a client, other appliances, Home Assistant's NUT integration, and an upssched timer that shuts down after a set time on battery
• Proxmox shutdown done right: what the host does at shutdown, the QEMU guest agent everywhere, start and shutdown order with timeouts, backups during an outage, and the HA shutdown policy on a cluster
• Coming back up: offdelay and ondelay, power-on after AC loss in firmware, ordering the comeback, services that wait for their storage, and Wake-on-LAN for machines off the UPS
• Test it before the storm: a status check from everywhere, upsmon -c fsd with the mains on, a plug-pull test, reading the evidence, the battery self-test and a battery calendar
• Measuring power use: wall meters, smart plugs and the Home Assistant Energy dashboard, turbostat and powertop for the CPU, and a measurement log with one change per row
• Cutting idle power: fewer machines, C-states and ASPM, intel_pstate and amd-pstate with an energy-performance preference, powertop --auto-tune without putting the UPS to sleep, disk spindown and ZFS reality, and unused devices
• Putting it together: the complete server and client configuration, the Proxmox settings, the numbers that have to agree, and alerts for the monitor itself, then a power-ready checklist and a cheat sheet

74 pages, 24 diagrams plus a chapter-opener graphic for every chapter, a power-ready checklist and a cheat sheet. PDF and EPUB. Homelab the Right Way, Book 17.

Not sure yet? Read the free sample first: the cover, the full table of contents and all of Chapter 3, "NUT on the Host" (how NUT is put together, installing it on the Proxmox host, finding the UPS with nut-scanner, ups.conf with the usbhid-ups driver, nut.conf, upsd.conf and upsd.users, upsmon.conf as the primary, starting the services, reading the UPS with upsc and listing its commands with upscmd), at https://payhip.com/b/OnKvx

Also in a bundle: Everything Bundle: every ebook in the store, $89 · Homelab Bundle, $59.