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




Chris Ramsden wrote:
> 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?

  https://wiki.debian.org/UEFI
  https://wiki.debian.org/GrubEFIReinstall

  and

  http://www.rodsbooks.com/refind/


> 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.

  yep.  do not install stable after testing is all i
can recommend at this point (based upon my experience)
and of course keep a working/verified netinst image 
handy.


> 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.

  i was rather surprised by it all but i'd been living
in the dark ages for years anyways.


  songbird