How to switch back from ssd to boot on emmc

Hi, Im a beginner and have bad English.
I do follow this => Memory Expansion for reComputer Series - Seeed Wiki
after $ ./copy-rootfs-ssd.sh and It work after reboot it change to ssd but i want to boot back to emmc.
with jetson nano dev kit J1020 Carrier Board
How I can do thank you (sorry my bad english).