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Re: Double boot (Windows & Debian) with UEFI mode

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On Mon, Dec 06, 2021 at 10:56:29AM +0100, frantal@libero.it wrote:
> Hello,
> 
> unfortunately, nothing David suggested worked, so I finally set it on in the bios Legacy (via F12) and then reinstalled Debian.
> 
> Now if I turn on, Grub appears with Debian that starts (even if it takes a while to boot) and if I want to use Windows, at boot, I have to click F12 and select boot with UEFI and then Windows 10 starts.
> 
> I tried to install os-prober on Debian, but it is already installed and doing update-grub, but Windows is not shown (Probably because it is inserted in the UEFI boot).
> 
> Is there any way to fix this mess?
> 
> Francesco

Hi Francesco,

That _definitely_ won't work. If one OS is installed using UEFI, then both 
need to be. Can you delete the Debian you've installed / reboot and use 
rescue mode in expert mode.

An expert install of Debian will allow you to specify where the boot files 
are. There is an option to install to a fallback location that should be 
found by any UEFI firmware. If you do that, it should work, and os-prober
should also pick up the existing Windows installer.

I think when I did this last time, I installed Debian first in UEFI mode and 
left space for Windows. Installing Windows thereafter it found the ESP
partition and installed Windows boot files there. I think it might have 
made Windows default boot and ignored Debian.

Rebooting Debian rescue mode and reinstalling grub and os-prober then found
Windows and put the items into grub so that it is sorted out.

All the very best, as ever,

Andy C.

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Thread

Double boot (Windows & Debian) with UEFI mode frantal@libero.it - 2021-12-06 11:00 +0100
  Re: Double boot (Windows & Debian) with UEFI mode "Andrew M.A. Cater" <amacater@einval.com> - 2021-12-06 13:00 +0100
    Re: Double boot (Windows & Debian) with UEFI mode David Wright <deblis@lionunicorn.co.uk> - 2021-12-06 17:20 +0100
  Re: Double boot (Windows & Debian) with UEFI mode Peter Ehlert <pb21a@sdi-baja.com> - 2021-12-06 13:40 +0100
  Re: Double boot (Windows & Debian) with UEFI mode David Wright <deblis@lionunicorn.co.uk> - 2021-12-06 17:20 +0100

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