uncpio is a rather simple binary CPIO extractor (File begins with 0x71C7 or 0xC771, made with cpio -oHbin). To acquire uncpio, run
pastebin get YbrVjRwa /bin/uncpio.lua
To use, make the directory you'll be extracting your CPIO archive to, cd into it, then run
uncpio path/to/your/file.cpio
And it will extract to the current directory. Currently only works in OpenOS, as far as I know.