A real Linux on my phone. Fedora 44 on a Galaxy S26 Ultra, on top of Android. No root, bootloader still locked, phone is completely stock. I don't really use it myself, I built it so an AI agent would have a proper Linux to sit in.
Setup is in docs/setup.md, about 20 minutes, and I ran every step of it on this phone. The AI side is in docs/ai-layer.md, including the parts that broke. There are two scripts in scripts/, one that does the inside-the-container setup for you and one little bridge thing the agent needs. The app that gives the agent hands is its own repo, the-body.
Termux is a Linux userland packaged as a normal Android app. Terminal, package manager, ssh, tmux, compilers, all of it inside one app's sandbox. It's genuinely good. But it's built against Android's libc instead of glibc, so it's its own thing and plenty of normal Linux binaries just won't run on it.
Then proot-distro takes a real Fedora root filesystem, drops it in a folder, and runs programs out of that folder while telling them the folder is /. A fake root. Fedora has no idea, it sees a normal / and gets on with it.
That fake root is the whole trick and it's also why it's slow. Every time a program asks the kernel for something, open this file, or list a directory, whatever it is, proot catches the request before the kernel sees it and rewrites the paths so /etc/passwd really means <that folder>/etc/passwd. It does that with ptrace, which is the same thing debuggers use to stop a program at every step. So the whole OS gets translated live, syscall by syscall. Or whatever the right term for it is.
I timed the same Python script in Termux and then inside the proot:
| native | inside the proot | |
|---|---|---|
| 300k bignum additions (pure CPU) | 2553 ms | 2558 ms |
| 3000 files created, stat'd, deleted | 303 ms | 2334 ms |
Arithmetic is free, because it never asks the kernel anything. Touch files and you pay about 8x. So npm install and compiling and git status on a big repo are all painful. A model that spends most of its time waiting on an API doesn't care.
It lies about the kernel too. uname -r says 6.17.0-PRoot-Distro and the phone is really on 6.12, which proot fakes so software that checks for an old kernel doesn't refuse to start.
You're root in there but it's proot pretending. You can't touch the Android system and nothing gets loaded into the kernel. systemd is installed but it can't run, because it isn't PID 1 and never will be, so systemctl just tells you the system wasn't booted with it. You start everything yourself.
Other than that it's a full Fedora. dnf works. Mine has about 1600 packages in it now, a JDK, gcc, node, python, tmux, llama.cpp that I compiled on the phone, a whole Android build toolchain. It's a Linux box in my pocket with better specs than the ThinkPad I built Bero-OS on, which is a bit annoying actually.
Because using it as a human on a phone is a pain in the ass. The on-screen keyboard is wrong for a terminal and the screen is tiny, and Samsung kills Termux in the background whenever it feels like it. Battery goes fast too. I end up sshing into it from my laptop, which kind of defeats the point of the thing being in my pocket.
So I turned it around. It isn't usable for a human on a phone, so the best thing to run on it is a CLI AI tool. I use Claude Code. Inside the proot it gets a real shell and real files and the phone's network. With the-body it gets the phone itself, so it can read the screen, tap things, answer a notification, and ping me with a yes or no question when it's stuck.
One tap on a home screen widget opens Claude Code inside the Fedora. Or it just runs on a timer with nobody touching it at all. That's how I ran a companion agent through most of the summer, waking up every fifteen minutes to deal with whatever had happened while I wasn't looking. That one isn't public and won't be, it knows way too much about my life, but how it was wired up is in docs/ai-layer.md.
I built a lot of this with AI help. The app too, and these docs. Claude Code did most of the typing and all the boring repetitive bits, I did the reading and the deciding, and honestly most of my actual time went on arguing with Samsung.
So it goes up here and not in a footnote at the bottom. The whole idea is a machine that an agent and I run together, so pretending otherwise would be strange.
Bero-OS is the same idea from the other end: there I'm building the machine from source, here the machine was already in my pocket.
| Layer | What it is |
|---|---|
| Android 16, One UI 8.5 | the phone, untouched |
| Termux 0.118 | Linux userland as an app. Its own packages, ssh on 8022, tmux, and the Boot / Widget / API add-ons |
| proot-distro 5.4 + proot 5.1 | pulls a distro image and runs it under the fake root |
| Fedora 44 aarch64 | the actual OS. zsh, starship, dnf, node, JDK, python, the lot |
| Claude Code 2.1 | the agent, installed normally, run with permissions off |
| the-body | Android app. Eyes, hands and a mouth over a loopback HTTP API |
I call the Fedora layer spirit and the app the body. There was a sky layer too which was just the Termux prompt. The names are Avatar, I'm not being deep about it.
- Slow as hell in the way measured up there. Fine for an agent that spends most of its time waiting on the network. Don't expect a laptop.
- Samsung kills things. Android's memory killer eats Termux's sshd every one to four days even with battery optimisation off, so anything that has to stay up needs something else watching it.
- Boot scripts don't run at boot. Android only tells apps the phone booted after the first unlock, so if it reboots at 3am nothing happens until I pick it up.
- adb over loopback doesn't survive a reboot, and nothing on the phone can bring it back. Anything built on adb is fragile, which is half the reason the body app exists.
- No real root, no systemd, no services.
- Only ever tested on this one phone.
MIT. The app and the writing are mine, the rest obviously isn't.