1. Rooted android device
2. PC with a debian based linux installed on it
3. SD card

First debootstrap the debian linux on the PC to be install on the android device:

sudo debootstrap --arch=i386 --variant=minbase --foreign stable ~/debian_bootstrap http://ftp.debian.org/debian/

• The above command debootstrap debian in ~/debian_bootstrap directory.
• Set --arch to match the android's architecture to fetch proper linux for it.
• Specify the desired debian release to fetch: stable, testing, stretch, jessie, etc.

At least one partition in the SD card is needed for linux. Format the partition to ext3 or ext4 filesystem:

Hint: use lsblk command to identify the partition to be formated, for example /dev/mmcblk0p1:

• ext3: sudo mkfs.ext3 -L "linux" /dev/mmcblk0p1
• ext4: sudo mkfs.ext4 -O ^metadata_csum -L "linux" /dev/mmcblk0p1
  • Note: Some android devices may not recognize ext4 partition with "metadata_csum" feature, so disable it when formatting.

Mount the formatted SD card partition:

sudo mount /dev/mmcblk0p1 /mnt/sdcard

Copy debootstraped files to mounted partition:

sudo cp -pfr ~/debian_bootstrap/* /mnt/sdcard/

Insert the SD card in the android device and get access to the android's shell via android apps like ConnectBot, JuiceSSH, etc. Or connect the device to the PC with a USB cable and get access to it's shell using adb shell command from the PC (USB debugging must be enabled in the android device).

Hint: Identify the linux partition on the android device by viewing the partitions file: cat /proc/partitions. For example /dev/block/mmcblk1p1

Set the linux partition's path in the linux.sh file as the LINUX_PARTITION variable. Default filesystem of SD card's partition is set to ext4. If the SD card's partition is formatted using ext3 filesystem, set the PARTITION_FS variable to ext3 in the linux.sh file.

Copy the linux.sh file to the android device in the desired location: /data/linux.sh (root needed) and make it executable:

chmod 770 /data/linux.sh

Execute the following commands on the android's shell in the first run only:

Login as root user:

su

Mount and chroot to linux:

/data/linux.sh

Finalize debootstrap process:

debootstrap/debootstrap --second-stage

Add password for the root user:

passwd root

Add desired DNS server to the resolve.conf file in order to enable domain name lookups:

echo nameserver 208.67.222.222 > /etc/resolv.conf

Create goups that are recognized by the andoird OS:

groupadd -g 3001 aid_net_bt_admin

groupadd -g 3002 aid_net_bt

groupadd -g 3003 aid_inet

groupadd -g 3004 aid_net_raw

groupadd -g 3005 aid_net_admin

groupadd -g 3006 aid_net_bw_stats

groupadd -g 3007 aid_net_bw_acct

groupadd -g 3008 aid_net_bt_stack

Any user in the chrooted linux that wants to access to the android's network should be in the aid_inet group. To add a USERNAME to that group execute the following command:

usermod -G 3003 -a USERNAME

In order to let the apt-get command to access to the internet via android's network, _apt user should be in the aid_inet group, too. Also the primary group of _apt user can be set to aid_inet by -g switch:

usermod -g 3003 -G 3003,3004 -a _apt

Prepare sources.list file:

echo deb http://security.debian.org/ stable/updates main contrib non-free > /etc/apt/sources.list

echo deb http://ftp.debian.org/debian/ stable-updates main contrib non-free >> /etc/apt/sources.list

echo deb http://ftp.debian.org/debian/ stable main contrib non-free >> /etc/apt/sources.list

Update apt repository:

apt-get update

Install ssh server to be able to login to the chrooted linux remotely:

apt-get install ssh

Note: To enable root login, add PermitRootLogin Yes in the /etc/ssh/sshd_config file.

To start ssh service automatically after chroot, add service ssh start command to the /etc/profile file:

echo service ssh start >> /etc/profile

Install desired packages and enjoy...

In order to chroot to the linux simpley execute linux.sh script: /data/linux.sh

To exit chroot, execute exit command in the chrooted linux.

To rechroot to the exited chroot, execute: /data/linux.sh -f

To unmount and kill chroot, after exiting chroot, execute: /data/linux.sh -k

To get help pass -h or --help switch to the linux.sh script: /data/linux.sh -h

In order to start a desktop environment and run GUI apps, install an X server app on the android and run it. One example is "XServer XSDL".

To forward the chroot display to the "XServer XSDL", execute the following command:

export DISPLAY=127.0.0.1:0 PULSE_SERVER=tcp:127.0.0.1:4712

To execute the above command automatically after chroot, add the above command to the /etc/profile file:

echo export DISPLAY=127.0.0.1:0 PULSE_SERVER=tcp:127.0.0.1:4712 >> /etc/profile

Install desired desktop environment, for example LXDE:

apt-get install lxde

To start LXDE desktop environment execute:

startlxde

To exit LXDE desktop environment simply press ctrl + c