From MEPIS Documentation Wiki
GNU cpio is a tool for creating and extracting archives, or copying files from one place to another.
For instance, cpio can be used to customize your grub-screen (background) as follows:
1. Make a directory test as root:
2. Copy as root /boot/grub/message to /boot/grub/test
cp /boot/grub/message /boot/grub/test
3. Change to directory test
4. Extract the archive 'message'
cpio -i < message
5. Replace the file background.pcx with your own design (you'll probably have to conform to the same format/size/name).
6. In order to get the proper archive make a textfile "name-list" with all filenames in test in it and then:
7. Copy files named in name-list to the archive
cpio -o < name-list > message