Simultaneous EFI and Legacy bootloader installation

[Mario Limonciello]

On 03/30/2016 09:11 AM, Lennart Sorensen wrote:
> On Tue, Mar 29, 2016 at 07:50:27PM -0500, Mario_Limonciello at Dell.com wrote:
> Certainly windows can NOT boot GPT disks if booted in legacy mode,
> and can only boot GPT disks in UEFI mode.
>
> So you sure can't choose GPT always if there is any other OS ever going
> on the machine because it won't be able to boot in legacy mode.
Can you comment what version of Windows you had noticed this behavior? 
We actually factory install as old as Windows 7 with GPT disks in legacy
mode at Dell.  We don't factory install Windows 8 or Windows 10 in
legacy mode.

> It is possible with grub to mix things although it isn't usually done.
> Booting legacy mode from a GPT disk requires an extra BIOS Boot partition
> to be created to install grub while booting in UEFI mode requires that
> there be a system partition for the boot loader.  So quite different.
Shouldn't it be possible to install GRUB into the partition boot record
(PBR) of the ESP?
> Both could in theory coexist, although you have to have booted in UEFI
> mode to update the NVRAM settings to even add Debian (or anything else)
> to the UEFI boot settings, so it can't be done while in legacy mode.
Yes, this scenario is why I was recommending in legacy mode to install
the removable path bootloader (\efi\boot\boot$ARCH.efi) by default. 
> So sure GPT is nice and all as a default if you only ever want to install
> Linux (and Linux that knows how to boot legacy mode on GPT) and never
> anything else.  Is that really a nice default to force on users?  I would
> think it isn't.
>