Grub and USBs

February 22, 2020

Having installed two GNU/Linux OSes on my laptop(a mid-2012 Macbook Pro), I'd planned on using KDE Neon as my daily driver, and using the other partition for distro hopping. I currently have Ubuntu 18.04 on it, but I plan on other OSes go in there to try out, and get a feel for. I ran a poll on Mastodon the other day to get others' opinion on what I should try next. It was three way tie between Elementary, Manjaro, and Arch (2 votes each). The only other vote went to Fedora, which I'm not keen on trying anyway.

I'm planning to do Elementary first. I downloaded the ISO and made into a bootable USB disk with Rosa Image Writer. The challenge came after that. I booted with the USB inserted, but Grub apparently doesn't detect USBs unless it is told to. So here's what I found from a Super User thread. This is what worked for me. The other answers were throwing all over the place and I'm glad I didn't brick the laptop doing something foolish.

Let me document the steps I ran for posterity.

While booting, press C on the Grub menu to get into the Grub console.
Do an ls, and run ls with all the results from the first ls to figure out which one is your bootable USB. For me, it was(hd0).
Run chainloader (hd0)/EFI/grubx64.efi.
Run boot to boot from the USB.

When you remove the USB and reboot again, Grub works as usual and gives you the options for the installed OSes.