Change Linux install to not boot with UEFI

Software & Operating Systems Linux
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1

So I was just wondering if there is a way to change a linux install, specifically ubuntu if that helps, to boot without UEFI without reinstalling it. I was just wondering because I'm trying to dual boot windows on my linux laptop and in order to boot the windows install disk I have to disable UEFI boot. Maybe I can just disable for the install and then re enable it and I'm just making this way to complicated. I don't know that's why I need your help.

2

I'm not an expert but I'm pretty sure that you can only change during an install. I think there's a different file (that I can't remember the name of) that is used to install for uefi instead of bios.

3

ok so I'll probably have to redo my whole setup again. Thanks anyways though

4

Yes you certainly can. You need to know 3 things:

  1. You have to boot an Ubuntu Live USB in BIOS mode. If you have a EFI motherboard make sure you know how to do this (disable EFI completely or enable Legacy mode and choose the correct option).
  2. You have to know your current disk label type. If your disk is formatted GPT, you need to add a small unformatted partition and enable the bios_grub flag on it. If not, you can't install the bootloader on the disk. If your disk is used 100% and you are really sure about this conversion, you can remove the old EFI partition and replace it with this bios_grub one.
  3. In this Live USB session, you need to mount your existing installation and chroot into it. Before doing the chroot, you need to mount /dev /proc and /sys to the mounted partition. Once you chroot into it as root, you can install grub-pc using "apt install grub-pc". It should take care of things. When asked, make sure you know where to install the bootloader!

If any of this is new for you, read up on it and be very careful. BIOS grub is not forgiving as is EFI (install grub to the wrong disk, and you can no longer boot Windows). If have all information required as mentioned above, it is actually very trivial and easy to do.

Good luck!

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5

HAHA! It worked! I thought for sure I was going to mess that up. Anyways thank you so much you just saved me alot of time.

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