Double boot (Windows & Debian) with UEFI mode


Joe wrote:
> I've never seen a legacy installation on GPT.

It is suspicious that the partition table has both, a GRUB2 legacy BIOS
partition and an EFI partition:

> >  dev / sda1 EFI system partition         (fat32) 100 MiB
> >  dev / sda5 grub2 core.img                      1.00 MiB

The BIOS partition substitutes for the space between MBR and the start
of the first MBR partition which once was used by GRUB code but in GPT
is occupied by the GPT header and partition table entries.
(The MBR itself can coexist with GPT. But its code size is restricted
to 446 bytes. All further brain has to be loaded by this MBR code from
some other place.)

I understand that it indicates a GRUB2 installation which boots via
legacy BIOS (or EFI's "CSM" mode).
An EFI partition indicates that some system is prepared to boot via
native EFI without CSM.

The original poster,, indicated that the installed
Debian is expected to boot via EFI. But i doubt that any MS-Windows
would create a GRUB2 BIOS boot partition.
So something is not as expected. Maybe that BIOS partition is just a
piece of debris from earlier states. But for now it is suspicious.

Have a nice day :)


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