for me its very easy just
CREATE IMAGE
- start rescue system - Krescue - Khadas Rescue system (still not complete sill in test mode )
dd if=/dev/mmcblk? bs=1M | gzip -c > MYIMAGE.img.gz
CLONE IMAGE
- start rescue system - https://forum.khadas.com/t/krescue-
gzip -dc MYIMAGE.img.gz | dd bs=1M of=/dev/mmcblk?
PS: i can write many other ways to clone systems, like via usb_otg, network, etc