SOP modifiy content of ramdisk.img, e.g., init.rc

Step 1. rename ramdisk.img.

$ mv ramdisk.img ramdisk.img.gz

Step 2. decompress ramdisk.img.gz through gunzip.

$ gunzip ramdisk.img.gz

Step 3. create a directory.

$ mkdir <dir-name>

Step 4. enter the directory that you just created.

$ cd ramdisk

Step 5. unpack ramdisk.img through cpio

$ cpio -i -F ../ramdisk.img

Note. After step 5, the whole ramdisk.img content decompressed.

Step 6. modify the content that you want.

Step 7. Generate pack list.

$ cpio -i -t -F ../ramdisk.img > list

Step 8. pack new.img.

$ cpio -o -H newc -O new.img < list

Step 9. Compress new.img

$ gzip new.img