[Xoom Android Development] LIV2:
Hey all,

I've seen a lot of people running linux on their android devices but chrooted under android and using a VNC client to make use of the chrooted install. quite messy and less than efficient IMHO, so I set out to install it natively on my Xoom

I've managed to get Debian installed on my Xoom with the only issues being no sound and no Bluetooth, this is due to the proprietary nature of the sound drivers for the Tegra, and the lack of documentation for the BCM4329 Bluetooth under linux. if anyone has any tips with these I'd love to hear them.

Anyway, since the Xoom is an android device with an unlockable bootloader from the factory this wasn't too difficult. the only issues were with the TegraFB and Touchscreen drivers. Thankfully Lilstevie from GalaxyLinux helped me out with the touchscreen driver and Robert Morell from NVidia provided a patch to Chromium for the FB which is here http://codereview.chromium.org/6672056

(Todo: Add guide for using WIFI, upload prebuilt images)

(Update: Fixed the links)

Basically all you need to do is build a root fs and a kernel for your Debian install. this is actually quite easy. here's how..

Contents

:

Requirements

Building the RootFS

Building the Kernel

Preparing the SDCard

Putting it all together

Rolling back to Android

Acknowledgements

Disclaimer

YOU DO THIS AT YOUR OWN RISK! I TAKE NO RESPONSIBILITY FOR ANY DAMAGES TO YOU, YOUR DEVICE,

YOUR COMPUTER, OR ANY OF YOUR PROPERTY OR SOMEONE ELSE'S PROPERTY

Requirements

A Rooted Xoom with ClockWorkRecovery Installed

[*] Make sure you have a nandroid backup. you will need this to boot back into Android!

A running install of Debian, Ubuntu might work too

An SDCard with at least 4GB for the install, preferably separate from your main SDCard and an SDCard reader for your PC

Android–SDK

An Arm–linux toolchain to compile the kernel, if you're lazy like me you can just use the one that comes with the Android NDK

This Xorg Config

Kernel sources

Fastboot tool

mkbootimg

Building the RootFS

Before we do anything we'll need to get the Wifi Firmware off the default install of Android

To do this run the following commands

# adb pull /system/vendor/firmware/fw_bcm4329.bin
# adb pull /system/etc/firmware/bcm4329.hcd

MAKE A BACKUP OF YOUR SDCARD AND YOUR XOOM USING CLOCKWORK RECOVERY BEFORE CONTINUING AND KEEP IT SOMEWHERE SAFE!

Now lets install the tools you'll need to create the rootfs

# apt–get install binfmt–support qemu qemu–user–static debootstrap

Once that's done, make a directory for the rootfs to sit in until it's ready for the SDCard and start installing the debian base

# cd ~
# mkdir deb_arm
# mkdir deb_arm/boot
# sudo /usr/sbin/debootstrap ––foreign ––arch armel squeeze deb_arm/ [url]http://ftp.au.debian.org/debian[/url]

Once that's done you'll need to copy across some qemu files so you can chroot into the deb_arm folder and finish the installation of the base system

# sudo cp /usr/bin/qemu–arm–static deb_arm/usr/bin
# sudo chroot deb_arm
# export LC_ALL=C
# export LANGUAGE=C
# export LANG=C
# cd /debootstrap
# ./debootstrap ––second–stage

once that's done you'll need to edit your apt sources, to do so run the following

# echo debandroid > /etc/hostname
# echo "deb [url]http://ftp.debian.org/debian/[/url] squeeze main contrib non–free" > /etc/apt/sources.list
# apt–get update

And then install any of the apps you'll want to run on your xoom, I'd recommend at least xorg, gdm3 and gnome, so

# apt–get install xserver–xorg–video–fbdev xserver–xorg–input–evdev gdm3 gnome initramfs–tools wpa-supplicant

You may find that you get an error like the following

Errors were encountered while processing: bluez gnome–bluetooth gnome–user–share gnome–desktop–environment

If you do, it's safe to ignore this for now. you can always complete the installation of any non–critical packages on the device. it seems to be something weird with the chroot or the qemu emulation of ARM (if anyone knows a way to fix this I'd be glad to hear it!)

Once that's done, you'll not only want to set your root password but you'll want to add a standard user account too

# passwd root
# adduser liv2
# addgroup ––gid 3003 inet
# usermod –aG 3003 liv2

The addgroup and usermod are especially important, the android kernel doesn't normally allow network access to non–root accounts. so we have to add the special group then give the user access to that group (or you could compile the kernel to not use the android paranoid network settings)

Once that's done, exit out of the chroot by hitting CTRL+D and copy the xorg config to deb_arm/etc/X11/ and copy in the wireless firmware you copied at the start

# mkdir ~/deb_arm/lib/firmware
# cp ~/fw_bcm4329.bin ~/deb_arm/lib/firmware
# cp ~/bcm4329.cal ~/deb_arm/lib/firmware

Building the Kernel

For this part, make sure you've extracted the kernel sources, and the android–ndk to somewhere, in my case they've been extracted in ~/Downloads

# cd ~/Downloads/Tiamat–AOSP–Tiamat–Xoom–798572c/
# export CROSS_COMPILE=~/Downloads/android–ndk–r5b/toolchains/arm–eabi–4.4.0/prebuilt/linux–x86/bin/arm–eabi–

# export ARCH=arm
# export INSTALL_PATH=~/deb_arm/boot
# export INSTALL_MOD_PATH=~/deb_arm
# make tiamat_defconfig
# make menuconfig

Once you've got the menuconfig screen up, go to Device Drivers > Character Devices > and enable "Virtual Terminal"

go to Device Drivers > Graphics Support > Console Display Driver support > enable "Framebuffer Console Support"

once you've enabled that, exit out and save the changes

Build the kernel and prepare it for use

# make –j2
# sudo make modules_install
# sudo cp arch/arm/boot/zImage ~/deb_arm/boot
# cp System.map ~/deb_arm/boot/
# chroot ~/deb_arm
# mkinitramfs –o /boot/initrd.img.gz `ls /lib/modules`

mkinitramfs may show some warnings like "warning: can't open /etc/mtab:" and "pkg: version '2.6.36.4Tiamat_Xoom–v1.4.4–Full_Throttle' has bad syntax: invalid character in version number" but it doesn't seem to have caused any issues for me.

Preparing the SDCard

Plug your SDCard reader into your computer and insert the card, you'll then need to partition and format it so make sure you've backed up the content of the card.

Partition it so you have two partitions, the first one being a FAT32 Partition for CWR and for anything you might want to use it for under Android.

Your second partition will need to be EXT3 and big enough to fit your debian install with some room to breathe (about 4GB in my case), you can check how much space you'll need for this by running du -sh ~/deb_arm

Once you've partitioned it, format the first partition as FAT32 and the second partition as EXT3. once you've done that you should put the SDCard back in your Xoom and make a new nandroid backup just to be sure

# sudo mkfs.ext3 /dev/sdb2
# sudo mkfs.msdos /dev/sdb1

Putting it all together

First we'll mount the SDCard on your PC and copy across the Root FS

Go to the folder you unpacked mkbootimg to and copy in the boot.img from your CWR backup.

Once you've done that, follow the below steps to create the new boot.img for Debian to use

# cd ~/Downloads/mkbootimg
# cp ~/deb_arm/boot/zImage .
# cp ~/deb_arm/boot/initrd.img.gz .
# mkdir out
# ./unpackbootimg –i boot.img –o out/
# ./mkbootimg ––kernel zImage ––ramdisk initrd.img.gz ––base "`cat out/boot.img–base`" \
––cmdline "root=/dev/mmcblk0p2 console=tty0" –o newimg.img

Now reboot your Xoom into Fastboot mode and insert the SDCard, this can be done by holding power + volume up until the screen goes black, then power it back on and hold down the volume down key

# cp ~/Downloads/fastboot .
# ./fastboot flash boot newimg.img
# ./fastboot reboot

Your Xoom should now boot up into Debian, on the login screen select the accessibility options and enable on-screen keyboard to log in.

Alternatively, if you happen to have a USB-OTG adapter you can just use a keyboard and mouse to interact with the system.

Going Back to Android

To Roll back to Android, simply boot into Clockwork Recovery, go to Backup/Restore > Advanced Restore and restore boot.img only, reboot and you'll be back in Android

Acknowledgements

Lopi from the IX Project was a great help, and so was everyone from #IX

Lilstevie from @GalaxyLinux provided the Touchscreen patches

Framebuffer Patch was originally provided by Robert Morell for the Chromium Project

RootFS instructions are based on info at the Debian Wiki