What i want to do is this.
Fisrt, from another host, Copy All rootfs partition of sdcard as cpio.gz
and copy it into rootfs
and boot raspberry pi 4 with this sdcard.
and make 3GB tmpfs
uncompress of cpio.gz into that tmpfs
and change the rootfs to tmpfs.
is it possible?
I tried to use cpio.gz as initramfs that i made above
but it is not working.