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Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM

On 2018-05-14 01:21, songbird wrote:
> Pascal Hambourg wrote:
> ...
>> I agree with the author. If you want to keep the existing EFI Windows 
>> installation and have a convenient dual boot with GRUB, you'll have to 
>> set up your favourite distribution to boot in EFI mode. If you want to 
>> go back to legacy boot, including for Windows, you'll have to 
>> repartition the disk to MSDOS format and reinstall Windows.
>   all i know is that if your bios doesn't boot in
> UEFI mode and you don't know anything about what this
> means you can end up installing Debian without UEFI
> support and then it can be rather fun to get it back.
>   i managed to have grub do an install to a stable
> partition without UEFI and i messed up the testing
> setup i had.  it took me some while to figure out
> what went wrong and how to fix it.  if you don't
> really understand grub rescue commands and there
> isn't a working system you can use to connect and
> find help for the commands you need to enter it's
> very frustrating.
>   the Debian UEFI pages helped a great deal but 
> there were other things i had to figure out coming in
> cold to UEFI.
>   how to create a /boot/efi partition, what goes in 
> it, mounting it, clearing and putting in new efibootmgr 
> entries, etc.
>   refind was useful and at least it does what i expect
> it to do.  grub, i dislike how it assumed things i
> didn't want to do.  alas, i didn't know how different
> UEFI was from bios mode.
>   i still haven't redone my efibootmgr entries but
> refind doesn't care, i can create custom entries in
> that config file and they work that is all i really
> need at this point.
>   songbird
Hmm, do you have any useful references?

I got a new Dell computer, shrunk the existing partitions down and
successfully installed grub2 and got a windows10/Linux multi boot using
grub. Then later I tried to upgrade my Linux and soon found that I was
getting error messages about grub not being able to find necessary
features on the boot device.

I tried to rebuild it with a clean install of Windows 10, reasoning that
if I could get it back to the original configuration, I could repeat the
original exercise. But alas, no, it remains stubbornly unable to install
grub2 alongside the windows bootloader. I got it to a state where I
could use the BIOS POST boot screen to choose a boot option, but this
wasn't the original successful arrangement where grub offered me the
Linux/windows loader choice.

I gave up, wiped windows and went through with a clean Linux install. I
don't really want windows that much, but it irks me that I haven't been
able to fathom out how to return to the original state in which it was
shipped. Your words hint at many things I became vaguely aware of but
totally failed to grasp. The other posters to this thread have at least
reassured me that it isn't easy or trivial to get right.