Re: Dual boot - first time using UEFI
On Mon, May 02, 2022 at 12:44:32PM +0200, Hans wrote:
> Hi folks,
>
> yesterday I installed debian bullseye besides a windows system. As UEFI could
> not switched off, I used gparted to make the windows partition smaller.
>
> Then used an usb-stick and installed bullseye as usual.
>
> However, the installer discovered UEFI and respected this, but atthe first
> boot, only windows could still be booted.
>
> But the bios allowed me, to boot into windows again (using the F12 key) , and
> I could start the installed debian.
>
> When I got it running, I tried to install grub again onto the MBR, which was
> successfull. But now appeared a blue screen, with choices: "Wait 10 seconds -
> go on - Restart - Do not ask any more" (similar, is from my remembers).
>
> After choosing "Do not ask any more", the next reboot showed me the well known
> grub starting screen.
>
> Well, everything is working, but the problem is: I have nothing learnt of
> this!
>
> Can ssomebody explain, what technically the grub installer did do? At one
> point it said "I have dicovered another EFI partition, shall I use it?" (or
> similar, it is from my remembers).
>
> Thanky for making things clear.
>
> Best
>
> Hans
>
Hello Hans,
I think this has also been covered in another thread here.
If Windows is the _only_ system on a disk, it hijacks the UEFI booting
process slightly :)
Most people never notice this because they don't dual boot ever.
If you install Debian first, it will install entries into the EFI
partition. If you then install Windows, it will set its own EFI entries as
first and does not recognise any other operating system.
If you have Windows installed first and then install Debian, it _should_
run os-prober and discover that Windows is already there and set it as
an entry within grub-efi and Grub's menus.
If not, you still end up with Windows first and have to boot using a
recovery disk somehow. Rerunning the grub install process at this point
does install os-prober and then the system "just works", I think.
See also the notes to Richard Owlett about how to dual boot a Debian/
Windows system in the other thread.
With every good wish, as ever,
Andy Cater
>
>
>
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