Install LINUX on your smartphone (chroot method)

This tutorial will show you how to install and configure a Linux Debian Virtual Machine hosted by your Android Smartphone, and accessible via VNC & SSH.

Summary

[I] Presentation

*General informations

This tutorial was made using a Samsung Galaxy S4 - ROM V4.2.2, but is possibly working with various other configurations.

There are few things you must be aware of before installing Ubuntu/Debian on youe Android Phone.

Ubuntu does not support earlier ARM CPUs like the ones used in the Motorola Cliq. Samsung Galaxy Fit (ARMv6), Samsung Galaxy Y, etc... The reason behind this is that your Android OS Kernel must support loop devices. Hopefully, most newer Android smartphones/tablets come with this support so we can mount our image as a loop device.

If not, you will either have to build your own kernel with support for loop devices or you can try an aftermarket ROM for your phone as most aftermarket ROMs come with support for it.

You need at least an ARMv7 CPU like the kind found in the Motorola Droid, Samsung Galaxy S,HTC EVO 3D, Sony Experia Play, etc. most newer phones (Hummingbird, Snapdragon, Tegra2, etc.).So you can Install Ubuntu if you have ARMv7 or newer Processor. If you have ARMV6 or any other moderate Processor don't be sad, because Debian supports the CPU on practically all Android devices, so if you prefer Debian, or you can't run Ubuntu, choose the Debian download link.

If you're not sure what CPU your device has, look up your device on http://pdadb.net/, click the link under CPU, and read the line for "Supported Instruction Set(s)".

[II] Prerequisite

*A "Rooted" smartphone

Read this article to get to know how to root your smartphone.

This Android app will help you know to check if your device is rooted.

*The SuperSU application (for rooted smartphones)

The SuperSU app or equivalent providing the 'su' tool.

*3GB of free space

For the good conduction of this tutorial it is necessary to prepare a 'root' folder for our debian distribution with (at least) 3 GB of free space. This free space can be stored on an internal memory or even external SD card.

Once this folder was created, be sure to remember the resulting path on your device as it will be required further. As an example, the "/storage/extSdCard/root" path will be used in this tutorial.

*A terminal emulator

It is required to download and install an Android Terminal Emulator.

*The Busybox toolbox

You have to download (and install) the Busybox toolbox. After launching it for the first time, select "system/xbin" as the installation folder.

*Allow "unknown sources" on your device

You may found here more details about the procedure to allow "unknown sources".

[III] Step 1: resource download and import

*Resouce download

Clic here to download the resource (Linux Debian 6.0 Squeeze).

*Prepare the resource

First of all, mount the SD card on your computer. then, extract the .tar.bz2 file you downloaded to your SD card. You should now have a folder named "linux" on the root of your card.

Finally, unmount the sdcard and replace it in your Android Smartphone. The following operations will be done via a terminal emulator directly from your android smartphone.

*Move the resource to the working folder

move the "linux/" folder from the downloaded archive file into the debian root folder mentioned at the begnning of this article (the "/storage/extSdCard/root/" folder).

[IV] Step 2: Working path update

*update paths

You have to modify the $sdcard variable of the files install.sh, ssh.sh, vnc.sh and scripts/linux for matching with your root folder (my path is: /storage/extSdCard/root/linux/).

• The fist line of the file /storage/extSdCard/root/linux/install.sh relating to variable $sdcard shall be updated to appears like:

sdcard=$(readlink -f /storage/extSdCard/root)

• The fist line of the file /storage/extSdCard/root/linux/ssh.sh relating to variable $sdcard shall be updated to appears like:

sdcard=$(readlink -f /storage/extSdCard/root)

• The fist line of the file /storage/extSdCard/root/linux/vnc.sh relating to variable $sdcard shall be updated to appears like:

sdcard=$(readlink -f /storage/extSdCard/root)

• The fist line of the file /storage/extSdCard/root/linux/scripts/linux relating to variable $sdcard shall be updated to appears like:

sdcard=$(readlink -f /storage/extSdCard/root)

In other words, the first line of each of those files shall be: sdcard=$(readlink -f /storage/extSdCard/root)

[V] Step 3: Files patch

*Patch of the install.sh file

The file install.sh (in this example at: /storage/extSdCard/root/linux/install.sh) shall be modified.

The existing instruction (more or less at lines 12-14):

sh $kit/scripts/fsrw

shall be replaced by this following new content:

busybox mount -o remount,rw /system

*Patch of the scripts/linux file

The file scripts/linux (in this example at: /storage/extSdCard/root/linux/scripts/linux) shall be modified.

The existing instruction (more or less at line 40):

mount -t ext2 -o relatime $loop $mnt

shall be replaced by this following new content:

busybox mount -t ext2 -o relatime $loop $mnt

[VI] Step 4: System installation

*installer execution

Launch the previously installed terminal emulator app and run the following commands:

user@android:#
su
root@android:#
sh ~/root/linux/install.sh

If no error occured, the installation of the resource is done!

[VII] Running and accessing the Debian system

3 possible ways of running and accessing this chrooted system is offered to us: the 'command-line', 'ssh' and 'vnc' ways.

• The 'command-line' way makes us accessing it through the terminal command-line prompt.
• The 'ssh' way makes us accessing it accross any SSH client.
• The 'vnc' way makes us accessing it through any of our favorite remote desktop app via the VNC protocol. Yes, this way will gives you an X server graphical display manager.

*Command-line access

Open the terminal emulator app and execute the following commands:

user@android:#
su
root@android:#
linux

If everything worked, you should notice that your prompt path has changed meaning that you are now under the chrooted system. As verifications, you may execute the following commands:

root@linux:#
uname -a
root@linux:#
pwd
root@linux:#
id
root@linux:#
ls /

*SSH Access

Open the terminal emulator app and execute the following commands:

user@android:#
su
root@android:#
linux SSH

You should now be able to connect to to the system using your favorite SSH client application.

*VNC Access

Open the terminal emulator app and execute the following commands:

user@android:#
su
root@android:#
linux vnc

The first time you run it, you will be prompted to create a VNC password. If you forgotted your password after multiple executions, you will have to redo Step 4: System installation.

Next, you may download a VNC client app on your device and connect to the debian system with the following informations:

• - address is: localhost:1
• - name: myfirstvncconnection
• - password: mypassworddefinedbefore

[VIII] Going further (Bonus)

*Linux on android virtualization projects

If you are interested by going deeper in this subject, you may have a look of various existing and promising projects like Linux deploy, kali-NetHunter or Ubuntu on android project

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