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AN EIGHT YEAR OLD PHONE BOUGHT BROKEN FOR THIRTY DOLLARS NOW RUNS A HOME SERVER ON NINE KILOWATT HOURS A YEAR

An eight year old Xiaomi bought broken for thirty dollars now runs a home server on nine kilowatt hours a year.

by postmarketOS community

FULL CAD BOM FIRMWARE DOCS

HomeAutomation

difficulty
●●●●○
time
a weekend-plus
license
GPL-3.0
repo
repo ACTIVE276 stars

WHAT YOU’LL NEED

Videos
1
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COMPAREE VERDICT

postmarketOS is a free and open source Linux distribution that extends the useful life of phones and tablets by replacing the closed software that usually kills them. Hardware Haven tested this with an eight year old Xiaomi Mi A1 bought beaten up for about thirty dollars, chosen because it is well supported. The catch is device support: only some phones run this properly, so check the list before you start. He first tried the Plasma Mobile image, found it clunky, and moved to a setup without a user interface. Docker and Home Assistant needed firewall rules (including mDNS) before networking behaved, and a Minecraft server ran into Java problems, so he narrowed the goal to Home Assistant. To avoid running a lithium battery on the charger 24/7, he removed the battery and fed the battery connector from a USB supply through a diode — a hack he calls janky. The result idles at about one watt and drew around six watts under a stress test; at a pricey 50 cents per kilowatt hour that is still only about four dollars a year. His verdict on the software was not a sales pitch: clunky, with real issues, and genuinely impressive for what it is. The thing most likely to go wrong is buying a phone that is not properly supported.

GOOD TO KNOW

  • —postmarketOS is GPL-3.0, free and open source with no commercial restrictions.
  • —Installation requires fastboot from Android SDK platform tools and pmbootstrap to build a custom image.
  • —Only a handful of devices have community-level support — the Xiaomi Mi A1 is one, but the phone in your drawer may not be on the list.
  • —Documentation exists but the builder says the process is clunky, with real issues, and requires SSH over USB networking to configure WiFi.
  • —Docker container networking required firewall rules before it behaved; this is documented in the community but not always obvious.
  • —No BOM or parts list — this is a software project repurposing an old phone, not a hardware build.

Parts to buy

3 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • Old phone with community-level support in postmarketOSFind
  • USB cableFind
  • Phone stand if you want it off the deskFind

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Can I build this?

Printnothing required
BuyAn old phone with community-level support in postmarketOS (check the device list first), a USB cable, a phone stand if you want it off the desk
ToolsA Linux machine or VM, Android SDK platform tools for fastboot, pmbootstrap, SSH, basic command line skills
SkillsComfortable with command line Linux, flashing devices via fastboot, SSH, editing firewall rules. This is not a beginner project — the builder says the process is clunky and he documents where it broke rather than glossing over it.
TimeA weekend-plus if you know what you are doing and your device is supported; longer if you hit firewall or networking issues
Cost$, dominated by the cost of an old phone (thirty dollars in the example) plus electricity at about four dollars a year
SafetyA phone battery left on the charger 24/7 can swell, which is why the builder removed it. If you do the same, feed the battery connector from a properly regulated supply (an adjustable buck converter set to about 4 V) rather than raw 5 V, insulate the joints, and keep the phone on a non-flammable surface. Beyond that, this is a software project.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

Videos

Broken phone as a home server (build by Hardware Haven)

Hardware Haven's full build video: choosing the phone, flashing postmarketOS, and running Home Assistant on it.

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Gallery

Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Check the postmarketOS device support list for your phone (Only devices with community-level support will work properly. If your phone is not on the list, this project will not work.)
  2. 2.Install Android SDK platform tools for fastboot(You will need fastboot to flash the phone.)
  3. 3.Install pmbootstrap and build a minimal image(Plasma Mobile was clunky on the Mi A1; a minimal image is the better answer.)
  4. 4.Use USB networking to SSH into the phone and configure WiFi(You can set up WiFi without touching the screen.)
  5. 5.Add firewall rules for Docker container networking(Docker will not behave until you do this; the builder documents it rather than glossing over it.)

Resources

Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.

KNOWN ISSUES

  • Buying a phone that does not have community-level support in postmarketOS and discovering pmbootstrap will not build you a working image.
  • Assuming Plasma Mobile will run well on old hardware — it is clunky, and a minimal image is the better answer.
  • Forgetting to add firewall rules for Docker container networking, which will break before you realise what is wrong.
  • Expecting this to be a beginner project — it requires command line Linux, fastboot, SSH, and the patience to debug when things do not work first time.
  • Treating the power and cost figures as universal — they are the builder's own measurements on one device, and your mileage will vary.

Will this work on the phone in my drawer?

Only if it has community-level support in postmarketOS. Check the device list first — only a handful of phones are supported properly.

How much does it cost to run?

At idle it drew about one watt, which is about 0.024 kilowatt hours a day or roughly nine a year. The builder points out that even at an expensive 50 cents per kilowatt hour that is only about four dollars a year. Under a stress test it drew around six watts, and your cost depends on your local rate.

Do I need to remove the battery?

The builder removed it. Running a phone battery on the charger 24/7 risks a swollen 'spicy pillow', so he replaced the battery with a USB supply soldered to the battery connector through a diode to drop 5 V to a safe level. It is a janky hack he says himself; a proper adjustable buck converter set to about 4 V is the safer way. After the mod the phone reports 99 percent battery, but that is the fake supply, not a real backup.

Is this easier than a Raspberry Pi?

No. This is harder, clunky, and requires more debugging. The builder says so plainly. The advantages are very low power draw (about one watt at idle) and reusing a device you already own.

Community builds

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Discussion1

FROM THE COMPAREE TEAM

About 0.024 kilowatt hours a day, roughly nine a year, for a phone running Home Assistant — but only if your phone is properly supported. What would you run on yours?

CompareeTEAM2mo agoedited

Practical notes from our verification: postmarketOS itself lives in the pmaports repository on the postmarketOS GitLab, and the device list on the postmarketOS wiki is where you check your phone before buying anything. The power and cost figures come from Hardware Haven's own test on a Xiaomi Mi A1 bought broken, and the video is upfront that this is not a tutorial: flashing, power, Docker networking and Java all caused problems along the way, and he ended up building his own headless image and removing the battery. Treat it as proof that an old phone can run a small server, not as a polished experience. The biggest trap is device support: the Mi A1 was chosen because it has community-level support, and many phones do not. Check yours first. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.

postmarketOS community

postmarketOS is a free and open source Linux distribution for phones and tablets, maintained by a community of developers whose stated mission is to extend the useful life of consumer electronics and give people full control over their own devices. The project exists because what kills a phone is usually closed software, not worn out hardware.

Web

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  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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