Chroot Debian On Android

Requirements

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

Debootstrap debian

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.

Prepare SD card

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.

Copy files to SD card partition

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/

Chroot on android

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

Initial setup

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...

Using chrooted linux

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

Running GUI apps and desktop environment

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