nix-on-droid/README.md

Nix-on-Droid

Nix package manager on Android, in a single-click installable package. This is not full NixOS running inside Android, but you get easy access to nixpkgs' vast collection of (precompiled!) software and the best package manager under the sun. It's prototype-grade quality as of now, but hey, it works!

It does not require root, user namespaces support or disabling SELinux, but it relies on proot and other hacks instead. It uses a fork of Termux-the-terminal-emulator app, but has no relation to Termux-the-distro. Please do not pester Termux folks about Nix-on-Droid.

This repository contains:

1. Nix expressions that generate a bootstrap zipball, which is then used to install Nix package manager on Android along with the nix-on-droid executable.
2. A module system for configuring the local Nix-on-Droid installation directly on the device.

It is only tested with aarch64 (64-bit ARM devices). It may also support x86 devices, but the developers don't own one and nobody has reported whether it actually works or not.

Sorry, it would not work on 32-bit ARM devices and it's not an easy feat to pull off.

Try it out

Prebuilt stuff resides at https://nix-on-droid.unboiled.info Install the APK, launch the app, press OK.

nix-on-droid and the module system

Config file

The Nix-on-Droid system can be managed through a custom config file in ~/.config/nixpkgs/nix-on-droid.nix as generated on first build, for example:

{ pkgs, ... }:

{
  environment.packages = [ pkgs.vim ];
  system.stateVersion = "19.09";
}

An alternative location is ~/.config/nixpkgs/config.nix with the key nix-on-droid, for example:

{
  nix-on-droid =
    { pkgs, ... }:

    {
      environment.packages = [ pkgs.vim ];
      system.stateVersion = "19.09";
    };
}

Currently there is no complete list of all available options. Please have a look inside the ./modules directory for all modules.

home-manager integration

To enable home-manager you simply need to follow the instructions already provided in the example nix-on-droid.nix:

1. Add home-manager channel:

   nix-channel --add https://github.com/rycee/home-manager/archive/master.tar.gz home-manager
   nix-channel --update
   

2. Configure home-manager:

   { pkgs, ... }:
   
   {
     # insert nix-on-droid config
   
     home-manager.config =
       { pkgs, ... }:
       {
         # insert home-manager config
       };
   
     # or if you have a separate home.nix already present:
     home-manager.config = import ./home.nix;
   }
   

nix-on-droid executable

This executable is responsible for activating new configurations: Use nix-on-droid switch to activate the current configuration and nix-on-droid rollback to rollback to the latest build.

For more information, please run nix-on-droid help.

Build stuff on your own

The terminal emulator part is probably not interesting for you, just download and use a prebuilt one. If you really want to rebuild it, you can just use Android Studio for that.

The zipball generation is probably what you are after. Get an x86_64 computer with Nix. Run one of the following:

nix build -f ./pkgs --argstr arch aarch64 bootstrapZip
nix build -f ./pkgs --argstr arch i686 bootstrapZip

Put the zip file from result on some HTTP server and specify the parent directory URL during the installation. To re-trigger the installation, you can use 'clear data' on the Android app (after backing stuff up, obviously). Now that we have an upgrade path for everything, this should not be needed anymore.

If you want to change the nix-on-droid channel to your custom one, you can do that either with nix-channel after the installation, or by using --argstr nixOnDroidChannelURL <URL>.

Note: The proot binary is currently not build on the android device because we are not able to pre-build and cache the proot package in cachix. The reason for that is that proot needs to be cross-compiled with bionic toolchain which results in different nix store paths in comparison to building it natively on the device.

The current workaround is to hardcode the path to the wanted proot nix store path in modules/environment/login/default.nix. During evaluation time on the android device this store path will be downloaded from the binary cache (https://nix-on-droid.cachix.org/). This in return means the proot derivation has to be present there or in any other binary cache configured in the nix.conf on the device.

Tips

• To grant the app access to the storage, use the toggle in the app settings (reachable from Android settings).
• If the terminal freezes, use 'Acquire wakelock' button in the notification and/or tone down your device's aggressive power saving measures.

Technical overview

OK, real brief.

Developer's device:

0. Required tools are compiled or downloaded in pre-compiled form
1. proot for the target platform is cross-compiled against bionic, (to fake file paths like /nix/store; think 'userspace chroot')
2. Target nix is taken from the original release tarball
3. Target nix database is initialized (with host proot and qemu-user)
4. Support scripts and config files are built with nix and the Nix-on-Droid module system
5. From these, a bootstrap zipball is built and published on an HTTP server

User's device:

6. Android app is installed and launched, bootstrap URL is entered
7. Bootstrap zipball gets downloaded and unpacked
8. 'First boot' begins, Nix builds the environment (or, possibly, pulls it from Cachix)
9. Nix installs the environment (login scripts, config files, etc.)

You can refer to a NixCon 2019 presentation talk for a more extensive overview of the subject.

Licensing and credits

Licensed under GNU Lesser General Public License v3 or later, see COPYING. Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.

Initially based off the official Nix install script (https://nixos.org/nix/install), presumably written by Eelco Dolstra.

Is deployed and used with a fork of Termux-the-terminal-emulator app, but has no relation to Termux-the-distro.

Previous project that did use Termux-the-distro: https://github.com/t184256/nix-in-termux