'''Unpacking:'''

Create a folder for example "initramfs", copy the file initramfs.cpio.gz in it. Unzip it:

{{{
$ gunzip initramfs.cpio.gz
}}}
Extract the cpio file and remove it after you're done:

{{{
$ sudo cpio -i -d -H newc --no-absolute-filenames < initramfs.cpio
$ rm initramfs.cpio
}}}
'''Packing:'''

{{{
$ sudo find . | cpio -H newc -o > ../initramfs.cpio
$ cd ..
$ gzip -9 initramfs.cpio
}}}