Nexus_boot_image_editor

Utilies for editing Nexus(or Nexus compatible) devices boot.img , then you don't need full Android source code to edit your boot images.

Prerequisite

Host OS requirement:

The unpacking task only works on Linux, the packing task can work on Linux & OSX. So the recommended OS is Linux.

Target Android requirement:

(1) Targeted boot.img MUST follows AOSP verified boot flow, which means it packs linux kernel and rootfs together, then sign it with OEM/USER keys.

(2) These utilities are known to work for Nexus (or Nexus compatible) boot.img for the following Android releases:

Branch: master

• Android AOSP master

Branch: Marshmallow

• Marshmallow (API Level 23)
• Lollipop (API Level 21,22)

You can get a full Android version list here.

Usage

Get tools via git:

git clone https://github.com/cfig/Nexus_boot_image_editor.git
cd Nexus_boot_image_editor

Then put your boot.img at $(CURDIR)/boot.img, then start gradle 'unpack' task:

cp <original_boot_image> boot.img
./gradew unpack

Your get the flattened kernel and /root filesystem under $(CURDIR)/build/unzip_boot:

build/unzip_boot/
├── bootimg.cfg
├── kernel
└── root

Then you can edit the actual file contents, like rootfs or kernel. Now, pack the boot.img again

./gradew pack

You get the repacked boot.img at $(CURDIR):

boot.img.signed

Advanced usage for ROM developers

If you have full Android source code, and have set up environment by envsetup/lunch, then the "pack" task will use $ANDROID_PRODUCT_OUT/root as rootfs.

. build/envsetup.sh
lunch xx-userdebug
cd <path_to_Nexus_boot_image_editor>
./gradew pack

If you have a rooted Android device connected via adb, you can also flash it with "flash" task:

./gradew flash

This will update the updated boot.img to /dev/block/by-name/boot.

example & test

An example boot.img has been placed at src/test/resources/boot.img, which is extracted from Nexus 5x(code: bullhead) factory images from Google, you can take it as a quick start.