Re: BIOS_grub GUID signature within an EFI partition?

[Bret Busby]

On 13/9/23 15:15, Andrei Borzenkov wrote:
> On Wed, Sep 13, 2023 at 9:53 AM Goh Lip <g.lip@gmx.com> wrote:
> > You cannot
> > mix efi and legacy install in the same disk
>
> You most certainly can as long as you have some way to select the boot
> method. You cannot use the same partition both as ESP and BIOS_grub,
> that's true.

For more than ten years, I had Ubuntu Linux installed on a HDD with MS 
Windows 8; Windows 8 used UEFI, and when I originally installed Ubuntu 
Linux (after Debian Linux, which coexisted on the computer, for a number 
of years) - I had three versions of Ubuntu Linux installed, at one 
stage, it was installed using (as Ubuntu 12.04 only allowed installation 
using) Legacy BIOS.

From what I understand, Ubuntu Linux has been able to be installed (at 
least, up until 22.04) using Legacy BIOS, although, a time came, when 
Ubuntu Linux (and, Linux Mint does it) installs by default, via UEFI.

When Legacy BIOS is used for installing Linux, it was done by entering 
the BIOS, switching off the malignant Secure Boot, and, choosing Legacy 
BIOS over UEFI, in the BIOS options.

Then, when Linux versions were installed, using Legacy BIOS, the GRUB 
boot options listed the Linux variant options, into which, to boot 
directly, and, the Windows Bootloader option.

This was all, on each of my computers, on a single hard drive (in each 
computer) upon which operating systems were installed; the primary HDD 
(for each computer).

I have not installed operating systems across more than one HDD (I use 
HDD, for what is/was regarded as a "hard drive" - on my latest computer, 
the primary "hard drive" storage (I can't remember the proper term for 
the static storage, that is not RAM or BIOS - it is too many years since 
I did computer hardware courses, for me to remember all of the 
terminology), is an NVVME (?) thingy - an SSD thingy, that is on a 
computer card that goes in a slot, and, whilst the computer does have a 
hard disk drive, it is not the primary "hard drive").

But, I have been installing operating systems, using Legacy BIOS, on 
computers that have had MS Windows 8 and later (MS Windows 8, from 
memory, was the first MS Windows version, to use UEFI and, the malignant 
"Secure Boot"), and, so, installing using legacy BIOS, on systems that 
had default UEFI booting, for more than ten years, now.

So, Legacy BIOS can be used to install operating systems, on the same 
"hard drive", that has a UEFI installed operating system, and, that has 
an EFI partition.

That is, on computers that have Legacy BIOS available.

With the destruction of computing, that has been caused by computer 
manufacturers, it is difficult to know whether Legacy BIOS is available 
on new computers (that have been deliberately made only partially 
functional, by the computer manufacturers, which is why it is no longer 
a good idea, to buy a new computer - more functional computers than new 
computers, can be found at rubbish tips).

..
Bret Busby
Armadale
West Australia
(UTC+0800)
..............