Dual boot with two drives that already have an OS on them.

Megahertz · 08 Feb 2022

My opinion:
- With a SSD it makes not much difference if you use Fast Start or not. On my Win 10 it is turned off. I never had the issues NavyLCDR mentioned on post #5. I have Win 7 and Lubuntu in one M.2 drive and Win 10 on a 2.5" SSD. Win 7 is my default (first BIOS option). I boot the Lubuntu or Win 10 launching the boot menu (F12) during POST.

- Correct if I'm wrong. If you add another Windows to a boot manager and you choose to boot from a different Windows it will reboot, taking more time than by launching a boot menu.

jimbo45 · 08 Feb 2022

Hi there
The easiest simplest way as I've often suggested is to have one EFI and one MSR partition. Then to have your Windows installs on physical vhdx files on whatever disk(s) you want to use, and have the main boot rec on HDD1.

At boot you will get a boot menu of the windows systems irrespective of what physical HDD they are on.

That's much more sensible IMO than having to get to the computers firmware bios menu to boot from a specific drive - and cloning say identical Windows systems to two HDD's on the same machine can also cause confustion with identical UUID's etc.

Multi-boot is simple, so is recovery / restore etc

e.g

Dual boot with two drives that already have an OS on them.-multios.png

cheers
jimbo

cereberus · 08 Feb 2022

NavyLCDR said:

I would disagree. First, if Windows 10/11 fast startup is enabled, it interferes with the ability to press whatever hotkey is assigned to bring up the BIOS or UEFI menu to select which drive to boot from.

Second, I have 2 laptops and one desktop computer. They have three different keys to bring up the BIOS (UEFI) boot menu, F12, F11 and F8. It's totally inconvenient to have to remember which key I have to press on which computer to bring up the menu, and hope that I tap the key at just the right time in the power-on sequence to get the menu.

Third, you can maintain the ability to independently boot each drive with its own independent OS and also have the convenient Windows multi-boot menu. I can have Windows 10 on one disk, Windows 11 on a second disk, and each disk can have its own EFI System Partition (or active partition with legacy BIOS) which contains a BCD that allows me to dual boot, regardless of which physical disk the computer's BIOS (UEFI firmware) boots from.

Totally agree with you.

If you create a dual boot entry as I originally stated, you can also boot into other and also create the same boot entry in reverse but those efi/boot entries are not seen whilst the bios is set to boot from the first drive. However, if you physically remove the first drive, the second drive will boot.

In other words, each disk will boot from a menu but can also boot independently if the other drive is removed (then you would simply remove boot entry of removed drive from bcd using msconfig).

I love it when people use the term "best" without defining its context!
Anybody who says the "best" option is to select option from bios is only stating a personal opinion, and cannot assume that suits others, or is even easy to do. It is reasonable to assume a user asking about dual boot has limited knowledge and they would want the simplest solution i.e. choose from a menu which is a standard setup.

Choosing from a bios is much more pc specific, and I have even see (admitted very old) bioses where you cannot select a specific hard drive and the hard drive boot order is defined by which SATA slot they are installed in i.e. SATA 0 boots before SATA 1.

NavyLCDR · 08 Feb 2022

cereberus said:

Totally agree with you.

If you create a dual boot entry as I originally stated, you can also boot into other and also create the same boot entry in reverse but those efi/boot entries are not seen whilst the bios is set to boot from the first drive. However, if you physically remove the first drive, the second drive will boot.

That's interesting. On my three computers, every EFI folder that is setup and populated properly shows up in my UEFI boot override menu - regardless of if they are on separate physical disks and even if I have two partitions on the same disk with EFI folders, they both show up as options.

Yes, @Megahertz, when I select an alternate OS from the boot menu in UEFI the computer does do a complete reboot to get to the selected OS.

Pendaws · 18 Feb 2022

Thank you all for your advice. I will think on it and try to sort it out properly. :)

ICY007 · 22 Feb 2022

Hi Pendaws
I am Using Bootit Bare Metal more than 10 years witout any problem
Yoy can boot 4 O.S in compatible mode,
8 O.S in extended mode
and you can eve boot a hundred O.S if You like
icy

- - - Updated - - -

Dslgirl · 26 Mar 2022

hi,
I would appreciate any help I can get,
i installed windows 7 on my internal hdd, on my Lenovo desktop 10 th gen
and have windows 10 on external h/d,
How can i dual boot, ?
but sometimes not turn external hdd on, just use internal hdd or just turn external on
or do both always have to be on,

Thanks

NavyLCDR · 27 Mar 2022

Dslgirl said:

hi,
I would appreciate any help I can get,
i installed windows 7 on my internal hdd, on my Lenovo desktop 10 th gen
and have windows 10 on external h/d,
How can i dual boot, ?
but sometimes not turn external hdd on, just use internal hdd or just turn external on
or do both always have to be on,

Thanks

You would want both drives to be able to boot independently of each other - so each needs to have its own system partition. You could try adding Windows 10 on the external HDD to the Windows 7 boot menu. I'm not sure how well it would work. If you are booted into Windows 7, the command would be:

Code:

bcdboot X:\Windows /d /addlast

Make sure to change the X: to match whatever drive letter the Windows 10 partition gets when it is connected and booted into Windows 7.

To boot from the external HDD by itself, you would need to select it from the boot override menu from BIOS.

Dslgirl · 27 Mar 2022

NavyLCDR

thank you very very much,

in windows 7 will try bcdboot X:\Windows /d /addlast and see if that works,

To boot from the external HDD by itself, you would need to select it from the boot override menu from BIOS
So what option on bios boot from would it be X: drive 1st on boot list and would that be recognized ?

thanks again

NavyLCDR · 27 Mar 2022

Dslgirl said:

NavyLCDR

thank you very very much,

in windows 7 will try bcdboot X:\Windows /d /addlast and see if that works,

To boot from the external HDD by itself, you would need to select it from the boot override menu from BIOS
So what option on bios boot from would it be X: drive 1st on boot list and would that be recognized ?

thanks again

It looks like the F12 or Fn+F12 is the key to press when you first power on the computer to get the boot override menu that would allow you to boot from the external USB drive with Windows 10 on it. How, exactly, did you install Windows 10 to the external HDD?