Android boot image editor

This post is a clone of the README of my github repo Android_boot_image_editor
It’s targeted at those who need to modify existing Android boot.img in place, without downloading full AOSP code.

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Utilies for editing Android boot.img.

Prerequisite

Host OS requirement:

Linux or Mac.

Target Android requirement:

(1) Targeted boot.img MUST follows AOSP verified boot flow, which means it packs linux kernel, rootfs , and a optional second state bootloader, 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:

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

You can get a full Android version list here.

Usage

Get tools via git:

git clone https://github.com/cfig/Android_boot_image_editor.git
cd Android_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.json
├── kernel
├── second
└── 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

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.

boot.img layout

Read layout of Android boot.img.
We now support os_version and os_patch_level.