Hi there,
I wonder that a “normal” boot- behaviour with CE (on eMMC) and Emuelec (SD) is working perfectly, but that there is no way to make this happen with CE (eMMC) and eg. Ubuntu or Android (both SD). Ok, Android is another chapter, but couldn’t it be possible to make a change to the boot.ini of Ubuntu? I’ve searched many topics in several forums, but there is unfortunately no solution for this (ok., maybe I haven’t seen all posts). Any idea for a workaround? Thanks!
Using petitboot is the way i have my N2 setup to boot into either N2 or Linux Mint. It takes care of the boot details.
Shoog
Maybe he wants dual boot from emmc via bootloader like grub
u-boot -> grub -> CE, android, ubuntu etc.
Ok., thanks for your reply! I tried petitboot, but had no success. Which settings are recommended? Always a bootloop to CE here…
No, I dont’t want to boot both from emmc, just CE from emmc OR Ubuntu from SD-card. It’s ovisiously a question of the boot order whitch is different in CE and the Hardkernel systems. Like I told above this works fine with Emuelec: without SD-card it boots into CE and if I insert the card it shows the CE-logo for a short time and then it boots into Emuelec! This also should be possible with other systems.
Use petitboot.
But first read instructions, there are many ways to do something wrong
As I told before I already used petitboot, but had no success. Inside of petitboot I can’t see my devices (emmc, SD) and have only the choice to boot from network, any devices, any disk devices or even any devices. All of them don’t work. Whitch instructions do you mean? Where can I find them?
Have a look at hardkernel/odroid forum.
I know petitboot will work, but it´s not Plug&Play.
It´s not CE related
You first have to update Petitboot to latest version (20191127), and then set it up to your needs:
Boot into Petitboot and test that your remote device can navigate through text menu options.
Read Disk info (top row) from recognized devices. Remember names and enter “System configuration”. Select Boot Order and Add Device. Mark one of your devices and press OK. Then select the other one, press OK. You can change Boot Order of selected devices by positioning on the one you need and pressing +/-. For the first run select “Auto Boot” → Disabled. After pressing OK for final selection, power cycle N2.
If all is done you can now choose in the menu which OS to boot. Booth OSs must be prepared to boot normally with SPI switch in right position, with only ONE device inserted, ie no installation can/should be done/finished using Petitboot.
Just to warn about petitboot
-yes you do have to update it to get it to recognise CE, the reason been it doesn’t recognise ext4 file systems out of the box
-the remote doesn’t work on mine (and I am not surprised since it was never setup) so you need a keyboard to navigate it
-on some petitboot versions it garbled the screen since it didn’t recognise my monitors resolution automatically, this was cured on the latest version
-once I setup petitboot it would only load CE through petitboot, a direct boot to emmc failed
-once setup mine defaults to boot from emmc (CE on emmc) automatically but this should be configurable
Shoog
Ok., thank you! I tried your workaround, but having still some problems here - In Petitboot it’s not possible to set up the boot order, after changing the first one (CoreElec - on eMMC) to the second place and the second to the first (here shown as NOLABEL, but it is Ubuntu) Petitboot shows only CoreElec…
After a restart there were both systems back again.
Restart from here, trying to boot CoreElec and yes, this works! Restart the system and now trying to boot NOLABEL, but now i’m sitting in front of a blank screen, nothing happens…
Normally, when only one card is inserted both systems starts without any problems, but my problem is that it’s not good to remove the eMMC for booting Ubuntu because I have built an optical S/PDIF-Port to the GPIO for my surround system and now it’s not so easy to open the case for every Linux booting, whitch I need only to have a good working webbrowser. If that would be inside CoreElec I’d have no problems at all. 
Obvisiously there is still a major problem with the boot sequence, so I’m still wondering that Emuelec has no problems with this (switch to MMC, SD card in ->Emuelec, without SD ->CoreElec.
Today I’m giving up so far, maybe I will work more on it tomorrow. Any further solutions are welcome!
Many thanks for your help to this point!
I installed Armbian, Ubuntu Mate, CoreElec on the uSD 64Gb card.
eMMC also has android.
4 I switch seamlessly between OS.
Petitboot works well enough.
I’d love to help you, but I don’t speak English. I can’t help but look at the forum, they’il help.
I opened a post in Hardkernel’s forum. To illustate the problem I uploaded some pictures. You’ll find my post here: https://forum.odroid.com/viewtopic.php?t=37438
Any help is welcome!
Ok., for those who have similar problems:
It was caused by the Samsung EVO Plus SD card! After swap to a SanDisk Ultra everything is running perfect.
Thanks to tobetter at the Odroid forum! 
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