Boot from emmc & rootfs on nvme even possible?

#1

I am striving to force Rock5B to boot from emmc, i.e. boot partition on emmc and to contuinue booting the system from nvme, i.e. root parttion on nvme. But after couple of evenings still no luck. I have ready bootable emmc with boot and root partitions. I can fully boot into the system from it. But I cannot manage to switch booting to root partition located on the nvme disk (to which I was booting earlier without any emmc involved).

I modified the /boot/extlinux/extlinux.conf (located on emmc) to point to the root PARTUUID on the nvme, but it does not boot. If I revert the change of the file, it boots to the root partition on emmc again. So I guess I am moving in the right way, but do not understand why it does not continue booting the root on nvme when the file is modified. It stops booting early showing just the black screen. No messages at all.

I tried this with the original SPI, as well as with the SPI flashed to nvme booting
mode. Neither one test was successful.

I went through this forum but did not find any useful hint for my scenario. Is it even possible?

Will be glad for any useful advice, thanks in advance.

#2

What operating system are you using?

#3

I’m using RebornOS and would like to keep it as my primary OS with its root partition on nvme. But now I want to have a possibility to try other OSes with their root partitions on emmc too.

Please note that I’ve been booting to RebornOS on nvme so far, no SD nor emmc involved in booting. So I (had) the full bootable RebornOS image on nvme and (had) flashed SPI with nvme u-boot image.

Recently I’ve plugged in the emmc with bootable RebornOS image. It booted fine from it when nvme was missing. But for whatever reason when nvme was inserted (alongside with bootable emmc), it still tried to boot from nvme even when SPI was flashed (and checked) with the zero image! And moreover it did not boot at all when SD (alongside with inserted emmc and nvme) with other then RebornOS was inserted. When SD with RebornOS was inserted (alongside with inserted emmc & nvme), it booted from it (from SD)…

As my last chance, yesterday I erased, i.e. rewrited the first empty 16MB space and the boot partition on nvme with some data in hope to make the nvme definitely not bootable. But even that didn’t helped.

Then, according to some hint in other thread here in the forum, I removed nvme, booted the Armbian from SD and installed it to emmc. Now it boots Armbian from emmc even if nvme is inserted back. After pointing the root to the RebornOS root on nvme in the armbianEnv.txt, it now finally boots from emmc and continue booting with the RebornOS on nvme. Voila!

Finally I managed what I wanted, but still do not understand why I have to use the Armbian boot process instead of the RebornOS’s to achieve that. I like the RebornOS boot more then the Armbian’s. Is the Armbian boot process somehow better, more solid or whatever else??? I would really like to understand it…