Can I turn an EFI-based USB Ubuntu installation into a plain bootable drive?

Question

So, here's the story:

I created a Live USB drive and booted with it on my new (UEFI) DELL laptop.
I installed Ubuntu on a second USB drive (full installation on a USB drive, not on the internal drive).
During installation, I told it to place GRUB on its own usb drive. What Ubuntu actually did though, was to install the main grub on the usb drive, however, it also added an EFI bootable option for Ubuntu, that "linked" to grub found on the USB drive whenever the laptop was booting. I was unhappy that it did that, because I didn't tell it to touch my EFI, but it did (there's no option during installation to tell it to not do that).
So Ubuntu now boots on the laptop by the EFI booting option, that "links" to grub found on the usb drive.
Now I'm sending that laptop back though and I'm getting a refund (because the N3060 CPU proved to be too slow), and I'm left with a USB Ubuntu that I want to be able to boot on any other UEFI laptop (just so I don't have to redo the installation again).

How do I convert that semi-bootable USB drive into fully bootable USB drive (like the one found on the Live CD, which is able to boot directly from USB on any laptop, and without the need for an EFI entry in the BIOS)? I tried booting you see on my other laptop with it, and it just doesn't boot (can't find grub, I'm guessing, there is no error message, just a blinking cursor).

So I want to convert that USB installation of ubuntu, that relied on EFI to link to grub, into something similar to the Live USB that is able to boot anywhere without any EFI entry! Is there ANY way to do this?

Possible duplicate of How can I repair grub? (How to get Ubuntu back after installing Windows?) — David Foerster, Jan 13 '17 at 23:08
It's not a duplicate, because what this person suggests in the answer is to install grub on /boot/efi/. However, in my case, the EFI system was installed on the EFI portion of the BIOS. So when I ran grub as suggested, and booted on another laptop, the system booted, but halted, not mounting any filesystems and complaining that it can't find a device that has a UUID that I don't know what it is. :( — Eugenia, Jan 13 '17 at 23:41
Possible duplicate of How do I install Ubuntu to a USB key? (without using Startup Disk Creator) — wjandrea, Jan 14 '17 at 00:16
Normally you have to copy /EFI/ubuntu twice to flash drive's ESP, once to /EFI/ubuntu and once to /EFI/Boot. And then in /EFI/Boot rename shimx64.efi to bootx64.efi as UEFI only boots from /EFI/Boot/bootx64.efi and the ubuntu shim expects more files to be in /EFI/ubuntu. https://ubuntuforums.org/showthread.php?t=2338836 — oldfred, Jan 14 '17 at 02:00
Concerning How can I repair grub? (How to get Ubuntu back after installing Windows?): if you go with the accepted answer you need to skip step 5 in accordance with the notice on that step since you don't want to (re-)install Grub in EFI mode. Also, my linked question has multiple answers; if you look at the second-highest voted answer you'll find one that doesn't require fiddling with the command line and I saw multiple experienced AskUbuntu members recommend that method for EFI-to-Legacy conversion or vice-versa. — David Foerster, Jan 14 '17 at 02:08
… The latter answer is also what you did according to your own answer. — David Foerster, Jan 14 '17 at 02:13

score 0 · Answer 1 · answered Jan 14 '17 at 00:09

Ok, managed to do what I wanted to do by using boot-repair. I installed it manually from a Live USB stick that I had booted on, running on a non-efi laptop, and did the necessary changes on my ubuntu usb drive in question, that was also connected but not booted from.

Can I turn an EFI-based USB Ubuntu installation into a plain bootable drive?

1 Answers1