From Newsgroup: alt.os.linux

As per subject, as I now have on the same PC some OSs - Ubuntu24, Windows7/10 - installed on an MBR disk and Windows 11 installed on a GPT/UEFI disk, I'd like if possible to find a way of booting any of
them, and MBR/GPT USB sticks, without constantly having to change the
BIOS settings on the PC.

Research into whether this is possible seems to produce mixed results,
mostly not, but a few suggesting it's possible, but I haven't yet found anything with clear and understandable instructions on how to achieve it.

My own gut feeling is that it should be possible, but, while I have a
good understanding of how a PC boots an MBR disk, I have less
understanding how one boots a GPT/UEFI disk.

Has anyone here been able to achieve this? Does anyone know of good
reliable sources of information about this?
--

Fake news kills!

I may be contacted via the contact address given on my website: www.macfh.co.uk
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From Newsgroup: alt.os.linux

On 2025-10-31 13:56, Java Jive wrote:

As per subject, as I now have on the same PC some OSs  -  Ubuntu24, Windows7/10  -  installed on an MBR disk and Windows 11 installed on a GPT/UEFI disk, I'd like if possible to find a way of booting any of
them, and MBR/GPT USB sticks, without constantly having to change the
BIOS settings on the PC.

Research into whether this is possible seems to produce mixed results, mostly not, but a few suggesting it's possible, but I haven't yet found anything with clear and understandable instructions on how to achieve it.

My own gut feeling is that it should be possible, but, while I have a
good understanding of how a PC boots an MBR disk, I have less
understanding how one boots a GPT/UEFI disk.

Has anyone here been able to achieve this?  Does anyone know of good reliable sources of information about this?

I think it might work if the system is UEFI with GPT disks, if you put
the other system in a partition, with boot code in the start record of
that partition. You would then need "something" in /boot/EFI to load
that boot code in that partition.
--
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;
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From Newsgroup: alt.os.linux

On 31/10/2025 12:56, Java Jive wrote:

As per subject, as I now have on the same PC some OSs  -  Ubuntu24, Windows7/10  -  installed on an MBR disk and Windows 11 installed on a GPT/UEFI disk, I'd like if possible to find a way of booting any of
them, and MBR/GPT USB sticks, without constantly having to change the
BIOS settings on the PC.

Have you considered running Windows 10 and Ubuntu in UEFI mode to
achieve the desired result? It's time to abandon Windows 7. There's
nothing you can do in Windows 7 that you can't do in Windows 10 or 11. I
know I am talking to a concrete wall which can't b
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From Newsgroup: alt.os.linux

On Fri, 10/31/2025 8:56 AM, Java Jive wrote:

As per subject, as I now have on the same PC some OSs  -  Ubuntu24, Windows7/10  -  installed on an MBR disk and Windows 11 installed on a GPT/UEFI disk, I'd like if possible to find a way of booting any of them, and MBR/GPT USB sticks, without constantly having to change the BIOS settings on the PC.

Research into whether this is possible seems to produce mixed results, mostly not, but a few suggesting it's possible, but I haven't yet found anything with clear and understandable instructions on how to achieve it.

My own gut feeling is that it should be possible, but, while I have a good understanding of how a PC boots an MBR disk, I have less understanding how one boots a GPT/UEFI disk.

Has anyone here been able to achieve this?  Does anyone know of good reliable sources of information about this?

It depends on whether this is a BIOS-mediated plan or a Pop-Up Boot
mediated plan.

The BIOS has a list of hard drives. If a drive
was not plugged in, maybe the BIOS moves on to
a new disk menu entry and considers it. But this does not
give much in the way of control, except if the user
is very confident that they know which disk
would be selected by the automation.

Whereas the Popup boot key, offers everything, on a UEFI/CSM BIOS.
The menu contents are determined by the ~25 second scan (for an HGST boot drive which is slow).

I press F11 on this MSI motherboard computer, to access PopUp Boot. When the scan is finished.
I press F8 on the Asus motherboqrd computer, to access PopUp Boot. When the scan is finished.

CSM First disk

UEFI Second disk # This could be a hybrid entry, or a hybrid DVD
CSM Second disk

UEFI Third disk

Windows Boot Manager # That's a UEFI, and it lists some sort of disk identifier
# The BIOS does not like multiple Windows Boot Managers, and
# it especially does not like them, if on TWO IDENTICAL DISKS :-)
# You can cursor one drive, and it selects the other drive.

UEFI USB stick

I don't know if Secure Boot can be enabled, without forcing the menu
to only consider UEFI disks. UEFI/CSM mode might be with no Secure Boot.
Once Secure Boot is enabled, only the UEFI disks should be listed (two entries in example).

In the PopUp Boot, you can cursor down to the item desired, and hit <Enter>

This situation is most likely to occur, when the disks don't
know anything about one another, and you have slid the drive in
as desired to achieve a result. The BIOS scans the drive set it finds at startup and puts entries for everything it finds. An entry that
hides a multiboot GRUB or Windows menu, would only occupy
one slot at this level, and once in a Windows tile menu, you could
select from a set of Windows OS partitions. Some of the partitions,
could even be on the other disk drives. If a disk drive is missing
and a Windows multiboot has entries, it is not fussed about a disk
drive gone missing... unless you hit <Enter> there and there is
no disk fitting that description present. The boot sub-menu in that
case is not validated on the fly.

I could see a boot sequence, using as many as three levels of menu.
For those of us who must be different. BIOS --> GRUB --> WindowsTiles
I think I accidentally did that at least once (not intentional).

*******

If you have a "control disk" that directs all booting on subtending
disks, then GRUB would be best for that, as it handles both its
own kind of OS, plus using OS-Prober it can include Windows OSes.
That's why the last paragraph has that example. I know I can get
an additional menu level, but putting the GRUB in the middle
of the sandwich.

*******

Ubuntu24, Windows7/10 - installed on an MBR disk
Windows 11 GPT/UEFI disk

USB Stick ???

OK, how I'd do that, is I make the first disk the "control disk".
As you likely installed Ubuntu24043 as a GRUB item and it was
installed second and GRUB now shows this when we perpetually
select the first disk so it steers the boot of other disks.

Ubuntu2404
Windows7
Windows10

If I do a sudo update-grub and OS-Prober is present while
Ubuntu2404 is running, and the Windows 11 disk drive is present,
then the GRUB may add the Windows to the menu during the update-grub run.
Now my control disk (the first disk) controls two disk drives.

Ubuntu2404
Windows7
Windows10
Windows11

In the BIOS, I set the BIOS to boot from the first (MBR) disk.
The GRUB comes up, I cursor down and select one of the four targets.

To launch the USB stick, I use the PopUp Boot key, and I select

UEFI USB # some of mine are showing up without the namestring
USB # for the USB hardware. The second one is CSM.

<ControlDisk1> # I would select this to get to the four entry GRUB menu

Some BIOS designs are just plain nasty, and follow no rules at all.
I've even had one report of a BIOS "that went nuts". I could not
make any sense whatsoever, out of the symptom description. The description makes as much sense as my mall elevator (I pressed "5" yesterday, the door closed, the elevator didn't move -- I pressed the "5" again, even though the "5" was already lit, and... off we went).

While you can wave hands about these things, YMMV.

Just a guess,
Paul
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From Newsgroup: alt.os.linux

In uk.comp.os.linux Java Jive <[email protected]d> wrote:

As per subject, as I now have on the same PC some OSs - Ubuntu24, Windows7/10 - installed on an MBR disk and Windows 11 installed on a GPT/UEFI disk, I'd like if possible to find a way of booting any of
them, and MBR/GPT USB sticks, without constantly having to change the
BIOS settings on the PC.

I think that should work without changing settings, although I haven't tried it.

You need to ensure CSM is turned on, that's support for legacy BIOS boot.
Then select which disc to boot from at boot time and it'll use UEFI if available and BIOS if not. You probably want Secure Boot turned off as that only works in UEFI mode.

Theo
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