edit initrd image

1. Rename:
mv initrd.img initrd.img.gz
2, Uncompress:
gzip -d initrd.img.gz
3. Extract: (WARNING!! without "--no-absolute-filenames" extracts in your root "/")
mkdir root
cd root
cpio -i --no-absolute-filenames < ../initrd.img
4. Do the editing
5. New archive:
find . | cpio -o -H newc > ../initrd_new.img
6. Compress:
cd ../
gzip -c initrd_new.img > initrd_new.img.gz
7. Rename:
mv initrd_new.img.gz to initrd.img