How to boot from eMMC but have root directory on an NVME?

[firefox-58]

partition your nvme the way you want it, make filesystems, move files over, edit fstab, check the boot config, then reboot.

i do the same thing on debian currently - my emmc just has boot partitions until i go all out with the SPI boot method.

Ok, there seems to be two partitions a BOOT_MNJRO and a ROOT_MNJRO.

I have found the fstab file but it has only one entry which would be for BOOT_MNJRO. So just add a new entry for the new "ROOT_MNJRO"?

Also where is the boot config and what should I change in it?

Thank you for the quick reply still a noob when it comes to file systems.

After bricking my PBP more than one time with flashing U-Boot i handled it in this way

1. install partitionmanger or gparted
   
2. format the NVMe and make one partition with EXT4 on it
   
3. mount the newly created NVMe partition to /mnt
   
4. "cd /mnt"
   
5. "mkdir dev proc sys mnt"
   
6. "rsync -aHxv --numeric-ids --progress /* /mnt --exclude=/dev --exclude=/proc --exclude=/sys --exclude=/mnt"
   
7. start partitionmanager KDE or gparted
   
8. edit the partition and rename the original partition label from "MNJRO_ROOT to MNJRO_ROOT_1 on the SD card
   
9. edit and rename the partition label of the NVMe partition to MNJRO_ROOT
   
10. apply all changes and reboot
    

Now the PBP boots from /boot on the EMMC and mounts / from the NVMe
Mission accomplished and no need for u-boot updates or renewals
NO warranties that it works the same way on other PBP's of other users !!!!