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Re: UEFI/"BIOS" booting, was Re: USB Install Fails, Complains about CD-ROM




> That said, there are other statements that are odd:

Not sure what you find odd about them:

>     "I really can’t recommend strongly enough that you do not attempt
>     to mix UEFI-native and BIOS-compatible booting of
>     permanently-installed operating systems on the same computer, and
>     especially not on the same disk. It is a terrible terrible idea
>     and will cause you heartache and pain. If you decide to do it,
>     don’t come crying to me." (under "UEFI booting: background").

Here he's just saying that there's a good chance you'll encounter
difficulties if you try that, and indeed in my experience the behavior
of such a config will depend on undocumented details.

>     "Disk formats (MBR vs. GPT)
>
>       Here’s another very important consideration:
>
>       If you want to do a ‘BIOS compatibility’ type installation, you
>     probably want to install to an MBR formatted disk. If you want to
>     do a UEFI native installation, you probably want to install to a
>     GPT formatted disk."

Same here (basically for the same reason: the behavior of the firmware
and OS when faced with a disk that has both a GPT and an MBR partitions
is largely unspecified and will vary depending on your system).

> I can't reconcile that with the system here, a Windows 8→10 UEFI laptop
> and GPT disk running linux in BIOS compatibility mode (here called
> Legacy mode by Lenovo) booting from an MBR on an ATA disk:

It's easy to reconcile: he doesn't say your setup is impossible or can't
work, he just recommends not to do that because you may encounter
unexpected difficulties.  E.g. in theory an upgrade to your firmware or
to one of your OSes could break it, tho in practice you're probably OK
at least until you move that setup to another machine with
a different firmware.


        Stefan