출처 :
https://unix.stackexchange.com/questions/64628/how-to-extract-boot-img
/*
download tools
*/
$ wget https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/android-serialport-api/android_bootimg_tools.tar.gz
/*
unpack recovery.img
*/
$ mkdir recovery
$ ./unpackbootimg -i recovery.img -o recovery
$ cd recovery
$ mkdir ramdisk
$ cd ramdisk
$ gunzip -c ../recovery.img-ramdisk.gz | cpio -i