[Discuss] Disabling UEFI and dual booting Linux and Windows

[Matthew Gillen]

On 11/05/2012 10:30 PM, Rich Pieri wrote:
> On Mon, 05 Nov 2012 21:04:29 -0500
> Jerry Feldman <gaf at blu.org> wrote:
>
>> I think it only affects the preinstalled consumer version of Windows
>> 8.
>
> I want to understand why. What is it about the pre-installed editions
> that makes them behave differently from the Enterprise edition and
> Server 2012? My suspicion is, as I previously wrote, incorrect device
> listings in the EFI boot settings. This could screw up any OS,
> including Fedora and Ubuntu, that is installed with Secure Boot enabled
> and a signed boot loader.

Just to give you a hint as to /one/ possibility regarding why 
pre-installed Win8 that was installed with EFI on can't boot with it off:

I had a laptop that I installed linux on.  Then one day I was messing 
with bios settings, and noticed that my SATA controller was set to IDE 
mode, instead of the much faster AHCI.  So I switched it, and linux 
wouldn't boot (couldn't find the disk).

The issue was that my distro (Fedora) builds custom initrd with only the 
drivers needed for your system (determined at install time), and then on 
every kernel upgrade builds the new one based on which drivers are in 
the old ones.  I eventually made it work by rebuilding the initrd image 
corresponding to my most recent kernel to include the AHCI driver, and 
after that any new kernel update worked fine as well.

So it may be something unintentional in terms of what they're doing to 
optimize their boot sequence.  Admittedly, mine was a bit of a rare 
case, since it involved the driver needed to access the disk, and that 
is one of the few drivers that absolutely has to be in the initrd (if 
it's not built-in to the kernel).  But I could imagine something similar 
in how they have a driver that needs EFI, and one that doesn't, and they 
load only the one that is appropriate for the system at install time.

I doubt the equivalent of "rebuilding initrd to include the other 
driver" is easy in windows...

Matt