Installing a Debian chroot on Android
This is an account of installing vanilla full-fat Debian squeeze in a chroot on Android.
This was tested on a Vodafone 845 ( a re-branded HuaWei u8120 / Joy / Ascend).
First, the phone was rooted by side-loading z4root
CyanogenMod 7.2.0-RC0 22b was flashed. This might not be necessary though
Set CPU to 710 MHz with the interactiveX governor. YMMV
- Side-loaded SSHDroid
- The SD card was formatted with the MBR scheme and a single ext3 partition was created. 15 sectors were left over
Then, on a workstation ( any architecture), insert the µSD card, and:
sudo debootstrap --arch=armel --variant=minbase --foreign squeeze /media/PHONE\ CARD/debian http://http.debian.net/debian
You might want to consider using --arch=armhf if your phone supports ARMv7. Note that then you also need to change squeeze to at least wheezy if not sid.
If you have a local mirror, replace the URL above with your local mirror.
Then remove the µSD card and replace it in the phone, start SSHDroid (which provides chroot command). Then SSH to the phone, then:
export SDCARD=/mnt/sdcard export ROOT=$SDCARD/debian export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$PATH mount -o remount,exec,dev,suid $SDCARD chroot $ROOT /bin/bash -l debootstrap/debootstrap --second-stage
Then build up the Debian system as you normally would a minimal installation.
Many thanks to all the people whose hard work made it so trivial for me to install the environment I know and love on my phone.
If you need to run binaries from inside the chroot outside the chroot, you can use ld.so:
export SDCARD=/mnt/sdcard export ROOT=$SDCARD/debian export LD_LIBRARY_PATH=$ROOT/lib:$ROOT/lib/arm-linux-gnueabi:$ROOT/lib/arm-linux-gnueabihf:$ROOT/usr/lib:$ROOT/usr/lib/arm-linux-gnueabi:$ROOT/usr/lib/arm-linux-gnueabihf cd $ROOT ./lib/ld-linux-*.so* bin/ls
Android pre-loads applications ( in some case that the user has never started) when there is free memory. This reduces the memory available to applications in a chroot.
It looks like the *_MEM properties in /init.rc along with the /sys/module/lowmemorykiller/parameters/minfree could help.
Go to the Android root ( start telnetd -l /system/xbin/bash from Android if you wish to telnet localhost from your chrooted SSH), then:
mkdir /dev/bin cp -a /system/bin/* /dev/bin/ cd /dev/bin/ mv app_process app_process.orig ln -s sleep-forever app_process # have to compile sleep-forever first mount -o bind /dev/bin /system/bin killall zygote # actually killed the pid because I don't have killall yet
If you wish to save some RAM them use symlinks instead.
The display is now blank and ready for SDL. The input devices only partly work with SDL on the 8120 ( write your own code to read /dev/input/event*) but graphics work well.
On android, you will need to add at least one group 3003 aid_inet for those processes which require access to creating sockets and other security guarded systems particular to Android.
exim4 chroot on Android
As well as altering inet access, the Debian-exim user will have to be added to group 3003. Further, if you experience trouble in the exim mainlog for creating sockets during DNS, try dropping privelages by adding "deliver_drop_privilege=true" to the exim4.conf.template file.