Sharing EFS / EFI partition between Windows 8 and Fedora 20

[Pedro Francisco]

Hi! Migrated this question from fedora-users, where I got not reply.
I hope someone here can reply :)

---------- Forwarded message ----------
Date: Mon, Oct 28, 2013 at 8:25 PM
Subject: Sharing EFS / EFI partition between Windows 8 and Fedora 20
To: Community support for Fedora users

Hello!
I've installed Fedora 20 on a Asus N550jv with no apparent issues.

Thing is, I accepted Anaconda's suggestion of having two EFS / EFI
partition, one for Windows (left untouched) and other for Fedora.

It is done, installed but... sounds messy.

Questions:
1- What are the advantages of having two EFS / EFI partitions?
I know some UEFI allow for one boot entry only per partition, thus
forcing to choose between Windows or Linux and leaving one with no way
to boot again the other; is that the only advantage of having two EFS?
I also know Windows 7 installer seems to balk when it sees two EFS;
I'd venture a guess Windows 8 has fixed this, can anyone confirm?

2- Any quick way to test if it would break, on my particular machine,
to have just one EFS with both Windows and Linux EFI boot files? Maybe
add two similar Windows boot entries and see if one of them disappears
after I boot Windows?

Thanks in Advance!
--
Pedro

[Kamil Paral]

> Hi! Migrated this question from fedora-users, where I got not reply.
> I hope someone here can reply :)
>
> ---------- Forwarded message ----------
> Date: Mon, Oct 28, 2013 at 8:25 PM
> Subject: Sharing EFS / EFI partition between Windows 8 and Fedora 20
> To: Community support for Fedora users
>
> Hello!
> I've installed Fedora 20 on a Asus N550jv with no apparent issues.
>
> Thing is, I accepted Anaconda's suggestion of having two EFS / EFI
> partition, one for Windows (left untouched) and other for Fedora.

Hello,

that is a bug, Anaconda should re-use the existing ESP. I don't have the bug number at hand, but Anaconda guys are trying to resolve this. You can ask for more info at #anaconda IRC channel during US working hours.

[Chris Murphy]

On Oct 31, 2013, at 2:44 AM, Pedro Francisco  wrote:
> I also know Windows 7 installer seems to balk when it sees two EFS;
> I'd venture a guess Windows 8 has fixed this, can anyone confirm?
>
> 2- Any quick way to test if it would break, on my particular machine,
> to have just one EFS with both Windows and Linux EFI boot files? Maybe
> add two similar Windows boot entries and see if one of them disappears
> after I boot Windows?

I'm not finding a UEFI spec proscription of more than one ESP per disk, but the behavior is unintended. The behavior of the firmware's built-in boot manager is OEM specific, so what might seem like a software bug can actually be "as designed" firmware behavior, including how it decides to display bootable OS's. It may be based on NVRAM entry, or parsing ESP contents, or some combination of the two. And this is perhaps the least frustrating part of UEFI.

Chris Murphy