Hi out there!
Because modifying an initial ramdisk is something I had to do every once a while and I am pretty oblivious when it comes to “exotic” commands, I will persist the knowledge at this point.
First of all, modern linux kernels (like everything above 2.6 or so) use an initrd that is a gzipped cpio-image (use file to be sure).
Extract an initial ramdisk
- Extract (i.e. gunzip) the gzipped image
~ $ mv initrd initrd.gz ~ $ gunzip initrd.gz
- Extract the contents of the cpio image
~ $ mkdir extracted && cd extracted ~/extracted $ cpio -id < ../initrd
(Re-)build an initial ramdisk
- Create the cpio image
~/extracted $ find . | cpio -H newc -o > ../initrd.new.cpio
- Compress (i.e. gzip) the image
~/extracted $ cd .. ~ $ gzip initrd.new.cpio ~ $ mv initrd.new.cpio.gz /boot/initrd-2.6.22-some-kernel
It might be possible to simplify some steps of this howto, but I tend to clarify things to avoid confusion.
I stumbled over the newc format of cpio. Actually, I think that there's not pretty much of a choice here.
The documentation doesn't say much about that, just use it.
Have fun, take care!