Linux: Create .cpio archive for initramfs

We suppose that our initramfs directory is under /tmp/initramfs
 To create the .cpio archive that will be loaded by the bootloader, we do:

1. cd /tmp/initramfs
2. find .  | cpio --quiet -c -o > /tmp/initramfs.cpio
3. cat /tmp/initramfs.cpio | gzip > /tmp/initramfs.cpio.gz
4. An voilà, /tmp/initramfs.cpio.gz can now be passed to the bootloader to be your root file system