pr

Android app that runs Linux distributions via proot — no root, no Termux required.

What it does

• Install and run Linux distributions (Alpine, Debian, Ubuntu, and 5 more) on any Android device
• Full package manager support: apk, apt-get
• Compile and run C, Rust, and other programs inside the guest
• targetSdk 35 — Play Store compatible

Supported distributions

Alpine, Debian, Ubuntu, Arch Linux, Fedora, OpenSUSE, Manjaro, Rocky Linux

How it works

proot uses Linux ptrace() to intercept syscalls and translate filesystem paths, creating a virtual root filesystem without actual root privileges.

The app bundles:

• Patched proot (C, ~90 source files) — handles Android-specific seccomp filters, SELinux, and W^X restrictions
• pr-cli (Rust, ~2K LOC) — replaces the original proot-distro.sh bash script
• Android APK (Kotlin + Compose) — install/login/remove UI with embedded terminal

Android compatibility

Android enforces several restrictions on app processes:

• W^X (Write-XOR-Execute): Prevents executing files in app-writable directories
• SELinux: Blocks certain filesystem operations
• Zygote seccomp: Blocks 18+ syscalls via BPF filter

Our proot fork handles all of these:

• SIGSYS handlers intercept blocked syscalls and emulate them in userspace
• The PROOT_LOADER mechanism uses nativeLibraryDir to bypass W^X
• Fake root (--change-id=0:0) makes dpkg and apt-get work without real root
• CLONE_VM/CLONE_VFORK stripping enables Rust's cargo build to work inside proot

Building

Prerequisites

• Android SDK with NDK r27c (auto-downloaded by build script)
• Rust toolchain with aarch64-linux-android target
• Java 17+

Build steps

# 1. Build proot
scripts/build.sh --arch=arm64

# 2. Build test binary
cd src/proot-integration-test && cargo build --target aarch64-linux-android --release

# 3. Build pr-cli (embeds test binary)
cd src/pr-cli && cargo build --target aarch64-linux-android --release

# 4. Copy binaries to APK
cp build/out/arm64/proot android/app/src/main/jniLibs/arm64-v8a/libproot.so
cp build/out/arm64/loader android/app/src/main/jniLibs/arm64-v8a/libproot-loader.so
cp src/pr-cli/target/aarch64-linux-android/release/pr-cli \
   android/app/src/main/jniLibs/arm64-v8a/libpr-cli.so

# 5. Build APK
cd android && ./gradlew assembleDebug

Testing

On-device (requires connected Android device)

# Install Alpine or Debian via the app UI, then:
adb shell run-as id.or.oo.pr files/usr/bin/pr-cli test alpine
adb shell run-as id.or.oo.pr files/usr/bin/pr-cli test debian

37 tests across 8 suites: distro, clone, readlink, gcc, rust, git, pipe, general

Host-side (pr-cli unit tests)

cd src/pr-cli && cargo test

Project structure

src/proot/                  # Patched proot C source
src/pr-cli/                 # Rust CLI — install, login, remove, test, backup, etc.
src/proot-integration-test/ # Guest-side test binary (TAP output)
src/scripts/                # Distro plugins (.sh), bootstrap.sh
android/                    # Android APK (Kotlin + Jetpack Compose + JNI)
scripts/                    # Host-side build scripts
vendor/                     # Git submodules (upstream proot, termux-proot)
docs/                       # Technical documentation

Documentation

Document	Description
docs/important-notes.md	Critical constraints, seccomp handlers — read first
docs/proot-improvement.md	Our proot fork vs upstream and Termux (27 sections)
docs/phase7-targetSdk35.md	How targetSdk 35 works (PROOT_LOADER mechanism)
docs/phase8-rust-support.md	vfork/CLONE_VM fix, link2symlink readlink fix
docs/phase9-integration-tests.md	Integration test suite (37/37 pass)

Credits

• proot — upstream proot v5.4.0 (GPL-2.0)
• termux-proot — Termux's proot fork with Android patches (GPL-2.0)
• proot-distro — distro plugins (GPL-3.0)

License

This project uses different licenses for different components. See LICENSE for details.

Component	License	Why
src/proot/ (C)	GPL-2.0-or-later	Derivative of proot (GPL-2.0) and termux-proot (GPL-2.0)
src/scripts/plugins/	GPL-3.0-or-later	Derivative of termux-proot-distro plugins (GPL-3.0)
src/pr-cli/ (Rust)	MIT	Clean reimplementation of proot-distro CLI
src/proot-integration-test/ (Rust)	MIT	Standalone test binary
android/ (Kotlin)	MIT	App UI and JNI bridge
scripts/, docs/	MIT	Build scripts and documentation