下载代码仓储 <https://android.googlesource.com/platform/system/extras>:

    git clone https://android.googlesource.com/platform/system/extras

选择对应的版本：

    cd extras
    git checkout android-4.1.1_r1

编译 simg2img:

    cd ext4_utils
    gcc -o simg2img -lz sparse_crc32.c simg2img.c

拆包android镜像文件：

    cd ../../
    ./extras/ext4_utils/simg2img system.img system.raw.img
    ./extras/ext4_utils/simg2img userdata.img userdata.raw.img

通过mount挂载镜像（Mac osx系统可以使用Paragon's ExtFS）：

    mkdir /mnt/my_system /mnt/my_userdata
    mount -t ext4 -o loop userdata.raw.img /mnt/my_userdata

编译 make_ext4fs:

    cd extras/ext4_utils
    gcc -o make_ext4fs -lz make_ext4fs_main.c make_ext4fs.c ext4fixup.c ext4_utils.c allocate.c backed_block.c output_file.c contents.c extent.c indirect.c uuid.c sha1.c sparse_crc32.c wipe.c

重新打包镜像：

    cd ../../
    PATH="$PATH:$(pwd)/extras/ext4_utils/make_ext4fs" ./extras/ext4_utils/mkuserimg.sh -s /mnt/my_system_dir my_system.img ext4 /tmp 512M