How to migrate image from Rock 4B to Rock 3A

I have some Rock 3A’s and recently made something on Rock 4B+.
I wanted to know if anyone has found a way to switch the system with their installations between two different Rock Pi models. I wouldn’t want to start all over again on the new Rock 3A’s that came my way.

Many thanks to anyone who has tried a method to this problem

I can only give you some general guidelines as I do not know what image was running on your ROCK 4, but below assumes you are running a Debian like system (as that is what we provide).

The 2 major things you need are bootloader and kernel.

First make a backup of your SD card.

Then boot the SD card in ROCK 4, install the above 2 packages.

Now you need to run lsblk to find out your SD card device name. It should be something like mmcblkX with X being a number. It should not have additional partitions like mmcblkXboot0, as those are unique to eMMC module.

You will first need manually update the bootloader. Run sudo /usr/lib/u-boot-rock-3a/ update_bootloader /dev/mmcblkX (replace X with the number you found above).

You will then need to update the boot entries. Either edit /boot/uEnv.txt or /boot/extlinux/extlinux.conf file. You should only have one of them available. You need to replace/remove ROCK 4 entries with ROCK 3 kernel.

Power off, and now you should be able to boot into ROCK 3. Some features might be broken as they may need SoC specific configs. So the recommended way is still remake everything from scratch.

Ok, thank you very much
I wrote down all the procedures and configurations I made on Rock 4B+ and with patience and a few days I will finish installing from scratch on Rock 3A and I will save this image for the next identical machines to be made, unfortunately for me Rock 3A was better than the 4B+, much more versatile in certain respects.