Windows 8 Dual boot lost after Fedora upgrade

[Chris Murphy]

On Wed, Jul 15, 2015 at 9:09 AM, Gary Stainburn
<gary.stainburn at ringways.co.uk> wrote:
> On Wednesday 15 July 2015 13:36:53 Chris Murphy wrote:
>> ++ GRUB_DISABLE_OS_PROBER=true
>>
>> This is why it's not making the Windows entry. I mentioned it previously.
>> So comment out that line in /etc/default/grub and then rerun grub2-mkconfig
>> -o ... to make a new grub.cfg in the proper location.
>>
>> Chris Murphy
>
> Hi Chris,
>
> Sorry I missed that. It's now included a chain loader entry for Windows,
> included below.
>
> As you suggested, I tried looking at the man page for grub2-mkconfig.
> Unfortunately, I don't have that man page installed so I tried googling it.
> The search pointed me to
>
> https://fedoraproject.org/wiki/GRUB_2
>
> which has only succeeded in confusing me more.  Based on the generated config
> file below, am I right in thinking that all I need to do to get GRUB to work
> and to allow me to boot windows is to:
>
> grub2-mkconfig -o /boot/grub2/grub.cfg

That's for BIOS systems. Fedora's GRUB does a screwy thing on UEFI
putting it on the EFI System partition, so you have to do:

grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg


> Assuming this is correct, I still need to work out how to get the laptop to
> boot GRUB instead of the Windows OS Boot loader.

efibootmgr -v    ## to list the boots
efibootmgr -o 0000,0001,0002....etc   ## to explicitly set the order,
use the boot numbers separated by commas.

Or do it in the firmware configuration/setup UI.

> ### BEGIN /etc/grub.d/30_os-prober ###
> menuentry 'Windows Boot Manager' {
>           chainloader /EFI/Microsoft/Boot/bootmgfw.efi
>           boot
> }
> ### END /etc/grub.d/30_os-prober ###

Yeah that's very clean. There's no set-root or search root or search
uuid or anything because the Windows bootloader is on the ESP, which
is also the GRUB root, and therefore there's no need to change the
root or search for a uuid to find the Windows bootloader. The path is
relative to the GRUB root.


-- 
Chris Murphy