Switching out a Pre-Built Android Image's Kernel

Posted on Thursday, September 15, 2011 in Blog By Zach Pfeffer

Many people just want to update the kernel of a pre-built Android build.

Find the Kernel

The first step is to find the kernel that was used in your build. For this post I’ll be using https://android-build.linaro.org/builds/~linaro-android/panda/https://android-build.linaro.org/builds/~linaro-android/panda/.

To find the kernel, click on the source-manifest.xmlhttps://android-build.linaro.org/jenkins/job/linaro-android_panda/285/artifact/build/out/source-manifest.xml link from the build. In this case the kernel is:

git://git.linaro.org/people/jstultz/android.git branch: linaro-android-3.0

(put together by John Stultz)

Get the Source

Cloning the repo:

$git clone git://git.linaro.org/people/jstultz/android.git
$cd android
$git checkout linaro-android-3.0

Grab the Toolchain

$wget --no-check-certificate https://android-build.linaro.org/jenkins/job/linaro-android_toolchain-4.6-linaro-master-with-generic-target/18/artifact/build/out/android-toolchain-eabi-linaro-4.6-2011.08-18-2011-09-12_08-38-17-linux-x86.tar.bz2

$tar -jxvf android-toolchain-eabi-linaro-4.6-2011.08-18-2011-09-12_08-38-17-linux-x86.tar.bz2

Find the defconfig

The defconfig can be found in the “complete output” link. You can get a copy with:

$wget --no-check-certificate https://android-build.linaro.org/jenkins/job/linaro-android_panda/285/consoleText
$cat consoleText | grep ARCH=arm

Rebuild the Kernel

From the consoleText output you can extract the make line and build with the toolchain listed on the build page:

$make ARCH=arm CROSS_COMPILE=$PWD/android-toolchain-eabi/bin/arm-eabi- defconfig android_omap4_defconfig && make ARCH=arm CROSS_COMPILE=$PWD/android-toolchain-eabi/bin/arm-eabi- uImage

Get the Images

Download the images and program them:

$wget --no-check-certificate https://android-build.linaro.org/jenkins/job/linaro-android_panda/285/artifact/build/out/target/product/pandaboard/boot.tar.bz2

$wget --no-check-certificate https://android-build.linaro.org/jenkins/job/linaro-android_panda/285/artifact/build/out/target/product/pandaboard/system.tar.bz2

$wget --no-check-certificate https://android-build.linaro.org/jenkins/job/linaro-android_panda/285/artifact/build/out/target/product/pandaboard/userdata.tar.bz2

Program the Images

The linaro-image-tools package allows you to easily program the compressed tar balls onto an SD card.

$bzr branch lp:linaro-image-tools

Insert an SD card:

$./linaro-image-tools/linaro-android-media-create --mmc /dev/sdc --dev panda --system system.tar.bz2 --userdata userdata.tar.bz2 --boot boot.tar.bz2

Update the Kernel

Mount the first partition:

$mkdir mnt
$sudo mount /dev/sdc1 mnt

If you do a

$ls mnt

You’ll see a uImage among the files. Copy the uImage that was built over.

$sudo cp arch/arm/boot/uImage mnt

Unmount and sync:

$sudo umount mnt
$sync

Examine the Serial Port

$minicom -D /dev/ttyUSB0 -w -C minicom.txt

Try It!

Insert the card in Panda and boot your custom kernel!