Re: problems dual booting Ubuntu 16.04 and Windows 10

[Pascal Hambourg]

Le 11/05/2018 à 21:16, David Collier a écrit :
> I am still confused though: how come the same firmware is booting Linux in
> legacy and windows in EFI mode (did I get this right from your
> explanations?).

Most PC UEFI firmwares can boot in legacy mode, i.e. the old BIOS way.
This can be confusing when booting a removable media which is both EFI 
and BIOS boot capable.

> The windows installation is pretty fresh, I can easily reinstall it, but
> how do I control which mode it is installed in (EFI vs legacy) - I don't
> recall any options for this anywhere.

You control it by forcing the firmware to boot the installation media in 
either mode. Either disable the boot mode you do not want, or select the 
boot mode you want.

> > Then ideally you must find a way to boot in EFI mode and start a shell
> > in Ubuntu.
>
> this also seems to indicate that I can control which mode the firmware is
> using to boot (how do I do that?), or is this a function of the image which
> is being booted?

This is a function of the UEFI firmware. Of course the image must 
support the selected boot mode.