Please refer to manual and see chapter 2.3  about internal storage installation.
   image-2022-04-20-10-57-15-032.png
Refer to SOP video. Take 256Gb m.2 SSD for example.
format your storage as ext4
b. $ sudo rsync -axHAWX --numeric-ids --info=progress2 / /media/adlink/ssd
c. Modify extlinux.conf in emmc
     APPEND ${cbootargs} quiet root=/dev/nvme0n1p1 rw rootwait rootfstype=ext4
d. Reboot

http://sftp.adlinktech.com/image/EOS-JNX/EOS-JNX_backup_from_microSD_card.mp4