TL;DR
MokListRT has nothing to do with nomodeset. It is a list of all UEFI Secure Boot keys that your Mac’s firmware trusts. Since Secure Boot is disabled anyways (Continuing boot since Secure Mode is disabled, as it says), this error is actually completely harmless — other than probably being annoying.
To get rid of the error:
- Head over to Rod Smith’s repository of common keys and download Microsoft’s third-party key
- Run
sudo mokutil -i /path/to/downloaded/file. Remember the password you enter here.
- On rebooting the Mac, it should ask you for the password you had entered previously.
- Víola! Now you shouldn’t see that error anymore. The password was just temporary, to make sure you were the same person between steps.
These steps are from Rod Smith’s website. He’s the creator of gpt-fdisk, and the Hermione Granger of disks, booting, and EFI.
MOKs
Machine Owner Keys are signatures that the firmware trusts, and will allow to boot. Of course, if Secure Boot is disabled, then any boot-loader will be given the go-ahead. Ever since BootCamp, Apple does hard-code Mac firmware with Microsoft’s public key — the one they use to sign the Windows boot-loader. But till date (as of 2020 Intel Macs), they do not pre-install the key that Microsoft uses to sign third-party software, like GRUB in this case. This is why your Mac refuses to add GRUB stuff to the MokListRT with all that drama, and why I — with my 2019 MBP — still have to disable Secure Boot to install Ubuntu.
N.B.: Macs have always had their own EFI, only conforming in majority to the general UEFI specification. I really hope the mokutil acrobatics work, but the 2012 MBP — why, even a 2020 (Intel) one — might just plain refuse to add any other keys into its list.
nomodeset
This is really just a kernel argument to prevent the kernel from loading-in hardware-specific graphics. Without context, I’m not entirely sure why you would need to do it, but I see no harm. If you’re experiencing any graphics-related issues, here’s how you can add that in (and no, you don’t need to do any wiping!):
sudo gedit /etc/default/grub (replace gedit with your favourite text-editor).- Find a line that says
GRUB_CMDLINE_LINUX_DEFAULT=.... If there isn’t one, make one.
- Replace the right-hand-side (
...) to "quiet splash nomodeset". (Just add nomodeset to the quoted list, if that was your sole objective. Btw, the presence of the option quiet hides the boot-up log output, and splash shows the familiar Ubuntu boot-up logo "splash screen".)
Hope this helps!
