Rainbow screen stuck raspberry pi 3b+

[Efriim]

@simpleethat
What would happen if he were to only update the boot partition with the firmware and kernel?

[ray3d]

@Efriim Well I was thinking that mainly this:

https://retropie.org.uk/forum/topic/16145/retropie-upgrading-raspbian-jessie-to-stretch

And is supposed work. I will backup my card to a img and try to make what says there. If doesn’t work I will use ext4 or what suggest @simpleethat and the other guys.

[Efriim]

What if you were to program_usb_mode and boot from usb; then chroot into the sdcard and upgrade from there?

[ray3d]

@Efriim I understand the boot from usb but how you chroot? And what would the purpose?

[Efriim]

@ray3d
400gb is a lot to back up, I don't want for you to lose it.
But if you want to try this the boot directory from my rpi3b+ with all the kernel and firmwares. I don't imagine the kernel will work with raspbian jessie but maybe the firmware will. No it probably isn't worth attempting, you would have your best bet using an ext4 mount and transferring the desired elements.

Anyway boot,

And don't go without backups.

I couldn't tell you how to chroot effectively. chroot changes the root directory so that a process and its child processes exist under the specified rootfilesystem. If you were then to run the update, I don't know if it would work or if it will break.

It sounds way too easy, I think you would invoke chroot like this
sudo chroot /mnt/sda2 /home/pi/RetroPie-Setup/retropie_setup.sh
or the mount would be a mmcblk0p2 you would chroot that instead, anyway I think you get the idea.
I'm not very sure, and it's hard to tell from the upgrade guide thread. I think the update process must upgrade the firmware.
I seem to remember one thing or another updating just that. It looks like you would need to update the sources.list @ /etc/apt/sources.list & /etc/apt/sources.list.d/raspi.list first.
I think the primary update was under retropie_setup>>configure>>raspbiantools>>Upgrade Raspbian Packages.

Additionally there is the USB boot problem, as far as I know the sdcard has to be removed for the USB to takeover. Then the risky part is putting the sdcard back into this voltage controlled sbc while it is on. It's probably fine, as long as you don't dick around with it.

[ray3d]

@Efriim Is working making the upgrade of the link posted here. Some minimal details to fix emulationstation but ran incredible well perfect everything after minimal fixes.

[Efriim]

@ray3d
That's great, did you require to use the kernel, or only the firmwares?

[ray3d]

@Efriim Imjust followed the instructions from that link to update, upgrade, and I fixed some libraries that had error but very easy nothing complex. And after all the upgrading if I type “lsb_release -r” I receive 9.8 I guess is stretch because 8 is Jessie. Then everything went very smooth and the 400 go intact.

[Efriim]

@ray3d Oh I see, thats good none the less. But how did you get into your system to update it?

[ray3d]

@Efriim Doing this step by step only:

https://retropie.org.uk/forum/topic/16145/retropie-upgrading-raspbian-jessie-to-stretch

After finished there are some errors in libraries that made crash emulationstation but they are easy to solve. Once it runs very well including with overclocking. With this fan “Noctua Premium Fan, Brown, NF-A4X10-FLX 5V” I could overclock and no problems.