Initramfs is a temporary “root” filesystem that help finding and loading your real root.
It is often located in /boot directory.
You can checkout the compress mothod by the following command:
They are usually compressed in gzip and archived in cpio.
This is how you can uncompress the initramfs:
$ mkdir -p /tmp/initramfs $ cd /tmp/initramfs $ cp /boot/initramfs.cpio.gz . $ gzip -d initramfs.cpio.gz $ cpio -i < initramfs.cpio $ rm initramfs.cpio
And this is how you can compress:
/tmp/initramfs# find . | cpio --quiet -H newc -o | gzip -9 -n > /boot/imagefile.img