Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition

[pelzflorian (Florian Pelz)]

I guess this is off-topic and we cannot learn anything about the
permissibility of mformat -k from Windows?

Michael Schierl already explained everything, but still:

I reinstate the Windows 10 USB installation medium’s content.

On Sat, May 11, 2019 at 07:31:23PM +0200, Thomas Schmitt wrote:
> > I do not know how to verify on Windows if the boot used UEFI.
> 
> You could zeroize the x86 machine code in the MBR:
> 
>   dd if=/dev/zero bs=1 count=446 of=/dev/sdb
>

After this dd it still boots.

> Then BIOS/CSM legacy mode should not have anything to start with.
> (It would be interesting to know whether there is useful machine code
>  in the MBR at all.)
> 
> Similarly you could rename the efi/boot directory in order to hide the
> EFI start-up programs and thus to prevent EFI booting.
> 
>

Renaming bootx64.efi to bootx64.efi.bkup makes the Windows 10 install
medium no longer appear in the boot device selection menu.

Regards,
Florian