F32 Upgrade Broke Dual Boot

Something strange is afoot. This morning I had a stable dual boot with F31 and Ubuntu 20.04. I had some trouble configuring grub when I initially set it up, so I’ve been selecting which to boot on startup via the boot device menu (it was in UEFI only mode). After completing the F32 upgrade, when I select Ubuntu in the UEFI boot device list, the screen just goes black. No error, no prompts, no reboot. No messages, indicators, or signs of any kind. It just hangs until I hold the power button.

I found that if I toggle the system to “Both UEFI and BIOS” boot mode I can boot into Ubuntu again though, and I’m presented with the grub menu after the boot device list which is new.

Two part question: I’m a bit fuzzy on the UEFI v. BIOS boot mode pros and cons. In a nutshell, is there any reason to think twice about just allowing BIOS boot, security or otherwise? If sticking to strictly UEFI mode is preferable, what might remedy the problem booting into Ubuntu? And in either case, what about the F32 upgrade could have caused the change in behavior?

So, you have the right mindset. What may have happened is that the Fedora upgrade simply destroyed the UEFI information for Ubuntu.

IMO, if you are not utilizing the benefits of UEFI, there’s no reason to set the BIOS to boot using UEFI. Simply set it to legacy and use it that way.

If you want to recover the UEFI stuff, there’s multiple ways to go about it. I’ve found that the best way is to just use Super Grub2 after any new OS installation or boot information change.

The easiest way may be to simply boot into Fedora and use Grub commands from there to:

  1. Detect other installed OSes:
    $ sudo os-prober

  2. Re-create the Grub information.
    $ sudo grub2-mkconfig