I bought a G1 in November having heard good reviews of them from the few people I knew who owned one and pleasantly surprised at how easy it was to type on the keyboard, which was the main problem I had had with iPhones.

Anyway, I haven’t really done much messing with it until the last couple of weeks when I discovered myself very bored while at home for the Easter break. Having heard it was possible a while ago I started off by rooting the phone and installing CyanogenMod (instructions here for those of you who want to try it), a replacement for the default Android installation, adding a features that haven’t been pushed down the line by vendors yet and a few extras such as the ability to store apps on the SD card, USB tethering and various Unix commands.

Having rooted the phone I was curious as to what I could now do and found it mentioned that it was possible to install Debian in a chroot since it already supports ARM EABI. I partially followed this post by saurik but came across several issues and shortcuts due to using CyanogenMod.

Here are some brief instructions to get Debian working on CyanogenMod:

Making a Debian image To avoid having to partition my SD card (I use it for various other things) I created a mountable image as follows (assuming you are running Debian on your computer too), to avoid confusion I also add an sdcard directory here that the sdcard will later be mounted in:

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apt-get install debootstrap
dd if=/dev/zero of=debian.img seek=749999999 bs=1 count=1
mke2fs -F debian.img
mkdir debian
mount -o loop debian.img debian debootstrap --verbose --arch armel --foreign lenny debian http://ftp.de.debian.org/debian
mkdir debian/sdcard
umount debian

As CyanogenMod comes with the Linux filesystem drivers and busybox you don’t need to worry about adding them which means a large portion of saurik’s instructions can be skipped. Mounting the Image Mounting the loop device caused some problems but I eventually found that it was looking for the loop devices at /dev/block/loop* rather than /dev/loop* which was fixed by adding a few ifs to the start of the mounting script.

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#!/system/bin/sh
if [ ! -e /dev/loop0 ]
then
	ln /dev/block/loop0 /dev/loop0
fi
	if [ ! -e /dev/loop1 ]
then
	ln /dev/block/loop1 /dev/loop1
fi
if [ ! -e /dev/loop2 ]
then
	ln /dev/block/loop2 /dev/loop2
fi
if [ ! -e /dev/loop3 ]
then
	ln /dev/block/loop3 /dev/loop3
fi
if [ ! -e /dev/loop4 ]
then
	ln /dev/block/loop4 /dev/loop4
fi
if [ ! -e /dev/loop5 ]
then
	ln /dev/block/loop5 /dev/loop5
fi
if [ ! -e /dev/loop6 ]
then
	ln /dev/block/loop6 /dev/loop6
fi
if [ ! -e /dev/loop7 ]
then
	ln /dev/block/loop7 /dev/loop7
fi
mount -o loop,noatime -t ext2 /sdcard/debian/debian.img /data/local/debian/mnt
busybox mount -o bind /sdcard /data/local/debian/mnt/sdcard
export PATH=/usr/bin:/usr/sbin:/bin:$PATH
export TERM=linux
export HOME=/root
export USER=root
busybox mount -t proc none /data/local/debian/mnt/proc
busybox mount -t sysfs sysfs /data/local/debian/mnt/sys
busybox mount -t devpts devpts /data/local/debian/mnt/dev/pts
if [ ! -e /data/local/debian/installed ]
then
	busybox chroot /data/local/debian/mnt/ /debootstrap/debootstrap --second-stage
	touch /data/local/debian/installed
fi

I saved this script as mountdeb.sh and the debian.img file in a folder called “debian” at the root of the SD card and mounted it on my G1 again. I used a terminal emulator (search Market for Terminal Emulator by ZTA Technologies). First to enable things like tab completion and command history I changed the initial command (done through the menu in the Terminal) to:

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su -c "busybox sh"

which nicely drops you in busybox as root instead of the poor implementation of sh that android comes with by default.

Running:

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/sdcard/debian/mountdeb.sh
chroot /data/local/debian/mnt/ /bin/bash

drops you into bash in your shiny new Debian installation from which you can use apt-get to install whatever you feel like.

Automating the Installation Since I didn’t want to have to type the above into the phone every time I wanted to use Debian on my phone and I also much preferred being able to use ConnectBot to access it I automated starting it as follows:

First I installed the dropbear ssh server onto the Debian install:

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apt-get install dropbear

This allowed me to either ssh to localhost from the phone or ssh in from my computer, which I was quite glad of after typing on the small keyboard for a while. Next to automate it.

Cyanogenmod provides facilities for auto running scripts using /etc/init.d/ however these all get run before android mounts /sdcard which means that we can’t run our script at this point unless we mount /sdcard ourselves (which does work but it means that none of the applications on the phone will be able to access /sdcard (I think there may be a way to change this by messing around with permissions but I haven’t tried it yet)).

Since init.d ran things too early I found an autorun application called Phone Prioritizer (available here (put the .apk in the attached zip on your SD card and open it with the package installer. Unfortunately you have to register on the XDA forums to get it), not on Market for some reason) which allows a script to be executed once the system has started up (Broadcast the BOOT_COMPLETED intent), it also had some options for running cron like scripts but I disabled these for the moment. To start the Debian chroot I edited /sdcard/phonePrioritizer/afterboot.txt (the file it checks after booting) to read:

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busybox sh /sdcard/debian/mountdeb.sh
busybox chroot /data/local/debian/mnt/ /usr/sbin/dropbear

Rebooting the phone I found I could immediately ssh in using ConnectBot on the phone. Some simple certificate setup later and I didn’t even need to type in a password from the phone to itself. :)

If anyone tries to follow these instructions let me know if you have any problems.