Android Chroot

Conveniently run ArchLinuxARM at near native performance on your rooted Android device.

Disclaimer:

/*
* Your warranty is now void.
*
* I am not responsible for bricked devices, dead SD cards,
* thermonuclear war, or the current economic crisis caused by you following
* these directions. YOU are choosing to make these modifications, and if
* you point your finger at me for messing up your device, I will laugh at you.
*/

This script uses root capabilities to be able to run. Please read this ENTIRE readme to limit the risk of harming your device, or even brick it. I really encourage you to use this tool with care, as I almost bricked my device and wiped all my data while developing it. Please see #Limitations/UNSAFE for further details.

Features:

1. Chroot Environment: The script sets up a chroot environment, isolating the Linux distribution from your Android system, ensuring an independent environment for running Linux applications.

2. Mounting and Unmounting: The script provides options to mount and unmount specific directories within the chroot environment, allowing seamless access to the Android system (/sys, /dev, /dev/pts and /proc) and the user's directories. This includes the user storage (/storage/emulated/0) and the Termux home directory (/data/data/com.termux/files/home).

3. VNC Server and Viewer: The script includes functionality to start a VNC server in the background, enabling remote desktop access to the chrooted Linux distribution. It also offers an option to launch a VNC viewer to connect to the VNC server with customizable profiles.

4. Firefox Integration: The script supports launching Firefox within the chroot environment using the bspwmrc configuration file.

5. Graceful Termination: The script ensures a graceful termination of the chroot session by unmounting directories and killing processes associated with the chroot environment. It offers options for forceful termination if necessary.

6. Multiple sessions: Before terminating and unmounting the chroot session upon shell exit, the script checks for any other parallel chroot session. If one or more are found, the current session will exit without impacting the state of the other concurrent sessions.

Limitations:

1. UNSAFE: Even though the chroot script logs into a non-su account, any abuse or risky behavior can and will impact your Android device. To limit risks, do not mount the system directories using the option --no-mount. Remember that the parent process of the session is root, which means that the ressource usage priority will be equal to the Android system itself, and will be prioritized over any user process. For instance, launching a program that exceeds the RAM capabilities of your Android device will result in a freeze and crash of the system, including the screen itself. Only the 10 second poweroff button can save you in such a case.
   
   Also, here is a stupid mistake I made that you should avoid: I tried to "sudo rm -rf" the linux distribution folder itself with /sdcard, /data/data/com.termux/files/home, /sys, /dev, /dev/pts and /proc mounted. That made my device crash so hard that the command wasn't able to complete, or at least that's what I believe. Just after entering this command, my screen froze and I realized my mistake. I crushed the power button as hard as I can, only to expect the next reboot to not complete, even though it miraculously did with no data loss.

2. Manual Setup: This script is NOT a ONE-CLICK solution. You will have to configure and dig stuff by yourself. You will need and use some Linux knowledge. If you don't, don't go further. ChatGPT will not unbrick your device.

3. Compatibility: The script's compatibility may vary depending on the Android device and the Linux distribution used. This script was tested on a Mi 11 Ultra and a Mi 9T Pro, running Miui 14 from xiaomi.eu, HyperOS 1 and 2 (also from xiaomi.eu) and LineageOS 20, based on Android 13 and 14, all similarily rooted with Magisk. The Linux distribution used is Arch Linux ARM and was configured to specifically run with chroot capabilities in mind. More on that later.

4. Root Access: The script requires root access in Termux or any other terminal emulator on the Android device, in order to use the chroot command in the first place.

5. Resource Requirements: Running a chrooted Linux distribution on an Android device may require significant system resources, including storage space, RAM, and CPU power.

Getting Started:

In this tutorial, we are going to use Arch Linux ARM. To use any other distribution, additionnal configuration and script editing is required.

1. Read the Disclaimer and the Limitations section above if not already.

2. Do not skip step 1.

3. Never copy and paste any of the following commands blindly. Please.

4. Ensure your Android device is rooted. Don't go further if you don't have any idea of how this can be done. For those who don't care about potentially breaking their device, search how to unlock your device's bootloader, and then flash Magisk after following every wiki or guide related to these subjects. Again, I am not responsible if this fails.

5. Download Termux, install git, clone this repo.

apt update -y && apt upgrade -y && apt install git wget nano sudo -y
git clone https://github.com/ThomasBaruzier/android-chroot ~/chroot
cd ~/chroot
chmod +x chroot.sh

6. Download the Arch Linux ARM distribution tarball. This is for ARMv8/aarch64 ONLY. Here is the official website: https://archlinuxarm.org/platforms/armv8/generic

wget -c http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz

7. Extract it under /data/archlinux

# Stop if mkdir errors, you probably already have a archlinux chroot on your system. If not, please stop following this tutorial, this shouldn't happen.
sudo mkdir /data/archlinux/

# You can ignore tar's "extended header keyword" warnings safely
sudo tar xf ArchLinuxARM-aarch64-latest.tar.gz -C /data/archlinux/

8. Modify /data/archlinux/etc/bash.bashrc:

sudo nano /data/archlinux/etc/bash.bashrc

Append the following code:

if [ "$(/bin/id -u)" != 0 ]; then
    HOME="/home/$(/bin/whoami)"
    cd
else
    HOME='/root'
fi

export LD_PRELOAD=''
export TMPDIR='/tmp'
export PREFIX='/usr'
export HISTFILE="$HOME/.bash_history"
export PATH='/system/bin:/system/xbin:/sbin:/sbin/bin'

9. Setup and configure the distribution (basic setup).

Enter chroot

./chroot.sh --mount-only
LD_PRELOAD='' su -c chroot /data/archlinux bash

Setup DNS (Use any DNS you like)

# In chroot
rm -f /etc/resolv.conf
echo 'nameserver 9.9.9.9' > /etc/resolv.conf
curl ip.3z.ee # check internet access

Setup pacman and packages

pacman-key --init
pacman-key --populate
sed -i 's/^\(CheckSpace\)/#\1/; s/^#\(Color\|ParallelDownloads\)/\1/' /etc/pacman.conf # disable `CheckSpace`, enable `Color` and `ParallelDownloads`
pacman -R --noconfirm linux-aarch64 linux-firmware linux-firmware-whence openssh net-tools # remove optional packages
while ! pacman -Syu --noconfirm sudo git base-devel; do sleep 1; done # rarely works first try because of network instability, so we loop it until it finishes
pacman -Sc --noconfirm # remove cache to save space

Setup users and sudo. Please modify the user value in chroot.sh, here:

android-chroot/chroot.sh

Line 4 in c23c9e7

user='tyra'

USER='tyra' # local user name, change me

userdel --remove alarm
useradd -m "$USER"
usermod -aG wheel "$USER"
passwd root # change root password
passwd "$USER" # change user password
EDITOR=nano visudo # uncomment `%wheel ALL=(ALL:ALL) NOPASSWD: ALL`

Basic arch install wiki steps

ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime # change Europe and Paris to your current localisation 
nano /etc/locale.gen # uncomment 'en_US.UTF-8 UTF-8' or another locale
locale-gen
echo 'LANG=en_US.UTF-8' > /etc/locale.conf # LANG is what you uncommented before
echo 'chroot' > /etc/hostname # set the hostname of your choice

Exit chroot:

exit

In Termux:

./chroot.sh --umount-only

10. If everything worked as expected, you can try using the script for the first time.

./chroot.sh

Warning: It is possible that the script kills itself while using the chroot session. In that case, the chroot session will not be terminated and unmounted correctly. To fix this issue, use ./chroot.sh --umount-only

11. The system should be around 630MB. Get my bashrc and execute clean() to save around 100MB

# In chroot:
curl -L 3z.ee/bashrc > ~/.bashrc
source ~/.bashrc
clean

Note: You can remove my bashrc after this if you don't like it

12. Build fakeroot with tcp ipc (dependency for yay)

# In chroot:
pacman -Rdd --noconfirm fakeroot
curl -O "https://ftp.debian.org/debian/pool/main/f/fakeroot/$(curl 'https://ftp.debian.org/debian/pool/main/f/fakeroot/' | grep -Eo 'fakeroot_[0-9\.]+.orig.tar.gz' | sort -n | tail -n 1)"
tar xvf fakeroot_*.orig.tar.gz
cd fakeroot-*/
./bootstrap
./configure --prefix=/opt/fakeroot --libdir=/opt/fakeroot/libs --disable-static --with-ipc=tcp
make
sudo make install
sudo ln -s /opt/fakeroot/bin/fakeroot /bin/fakeroot
fakeroot --version # verify fakeroot was correctly installed
cd ..
rm -rf fakeroot*

13. Install yay, a popular package manager for the AUR

# In chroot:
git clone https://aur.archlinux.org/yay-bin.git
cd yay-bin
makepkg -si --noconfirm
cd ..
rm -rf yay-bin
yay --version # verify yay was correctly installed

14. Setup the VNC server and viewer, bspwm, sxhkd, and firefox.

<TODO>