Step by step to create/modify ramdisk.img

ramdisk.img is included in the google android sdk, it exists in folder $SDK_ROOT/tools/lib/images/ramdisk.img. The ramdisk.img included in the google android sdk is a gzipped ramdisk.cpio file.

Here is the steps:

1. Upload the ramdisk.img to your linux machine
2. Change the ramdisk.img name to ramdisk.cpio.gz, and extract it by: # gzip -d ramdisk.cpio.gz
3. Create a temporary folder, say tmp, copy ramdisk.cpio to tmp folder
4. Extract the ramdisk.cpio in the tmp folder with command: # cpio -i -F ramdisk.cpio
5. Remove the ramdisk.cpio in the tmp folder, and make any changes you want to the extracted ramdisk.cpio in tmp folder
6. Recreate the ramdisk.cpio with command: # cpio -i -t -F ../ramdisk.cpio | cpio -o -H newc -O ../ramdisk_new.cpio

Some notes:

1. I change ramdisk.img to ramdisk.cpio.gz, and unzip it. It is because I find the -z parameter is not supported with my cpio. I tried the latest cpio (2.9), it doesn't work too.
2. Check cpio version by # cpio --version. I'm using cpio version 2.4.
3. Find the latest cpio (v 2.9) on site: gnu cpio
4. Notice that in step 6, the command includes two O's. First o is lower-case, second is up-case.
5. Notice in step 6, please remain ramdisk.cpio in up folder of tmp folder. The command need it there.