Making a Linux home server sleep on idle and wake on demand (2023)

Original Article ↗ Hacker News Discussion ↗

Power usage realities and measurement

  • Several commenters report very low-power home servers (7–15 W mini PCs / Mac Mini) and argue that elaborate sleep/wake setups make less sense if hardware already sips power.
  • Others have “pig” servers idling at 100–130 W, often due to many drives, SAS controllers, or older/server-grade platforms; heat buildup is a real annoyance.
  • Power meters and smart plugs (Kill‑A‑Watt, Sonoff, IKEA, Shelly, etc.) are widely used to measure draw; some share UK numbers (~£25/year per 10 W 24/7).
  • Debate over how low idle can realistically go: some claim ~1 W with very careful hardware/ASPM/C‑states, others say that’s a “unicorn” and <10 W is more realistic. Intel is praised for deep C‑states; modern AMD chiplet designs are said to idle higher.

GPUs, AI servers, and “big iron” at home

  • One thread discusses huge GPUs (e.g., RTX 5090) with high idle power; advice includes avoiding such GPUs in backup boxes, using nvidia‑smi power limits, and headless/server drivers.
  • Counterpoint: some home servers are explicitly for AI experiments, not just backups, so high‑power hardware is expected.

Alternatives to the Pi sleep proxy approach

  • Many suggest simpler WoL‑based setups: enable WoL in BIOS, send magic packets from router, another host, or over the internet with static ARP on the router.
  • Others use:
    • SBCs or microcontrollers (Pi, RockPi S, ESP32) as always‑on WoL emitters.
    • PiKVM / NanoKVM or ATX control boards to simulate power‑button presses and provide out‑of‑band management.
    • Smart plugs with scripts, or even mechanical timers plus RTC wake for backup windows.
  • Some want extra features like port knocking for wake, or mimicking Apple’s Sleep Proxy so clients don’t need to know about WoL.

Complexity vs savings vs tinkering

  • Critics say the described system is over‑engineered to save only modest electricity, introduces brittle dependencies (SD cards, IPs, Python libs), and ignores mature tools (rtcwake, powerprofilesctl, Windows Task Scheduler).
  • Defenders point out high electricity prices (especially in parts of Europe), cumulative savings across multiple servers, environmental aesthetics, and the intrinsic fun/education in hardware–software tinkering.
  • There’s broad agreement that if you’re willing to use WoL magic packets explicitly, much simpler and more robust solutions are possible.

Hardware quirks and tips

  • Some motherboards cut power to NICs/USB in sleep, breaking WoL; workarounds include BIOS options (disabling certain energy modes), using special USB hubs, or different NICs.
  • Tools like powertop are recommended to tune idle power, with warnings that some aggressive settings can hurt responsiveness.