[RESOLVED] revert dual boot

[monon]

I have a desktop PC dual booting Kubuntu 22.04 and Windows 10. I bought the PC with Windows installed on a SSD. I installed a hard disk on which I installed Kubuntu. I left the SSD connected while I did the Kubuntu install. Grub grabbed Windows as well as Kubuntu, and now Grub controls the booting of both OS's. My intent was to install the two OS's as separate devices and select the boot device through the BIOS. Is there a way I can safely separate the two OS's so that Grub will handle only Kubunbu, and let Windows handle itself? I would like to do this without re-installing everything. Thanks for any help.

[Schwarzer Kater]

Add GRUB_DISABLE_OS_PROBER=true to /etc/default/grub (you can use Kate for that - or of course Konsole and the CLI text editor of your choice like nano or vim).
Save it and sudo update-grub in Konsole afterwards.

GRUB does not touch the Windows boot loader, btw (at least not with UEFI) - even if Windows (or other systems) are listed in the GRUB boot menu you can still use your UEFI boot menu (or legacy BIOS setting if they are on different drives) to boot the systems independently.

[monon]

Thank you. I'll be trying this soon. I think this also means that if I disconnect the Linux disk, the PC will boot up in Windows. Right?

[Schwarzer Kater]

In most cases it should - but it can also depend on your UEFI (or legacy BIOS - you did not tell us which one your computer uses) and its settings.

[jlittle]

My intent was to ... select the boot device through the BIOS. Is there a way I can safely separate the two OS's so that Grub will handle only Kubunbu, and let Windows handle itself?

I wonder why. Selecting the OS through the BIOS is less easy than choosing Windows through the grub menu. It's not like it makes any difference to Windows, or that grub touches the Windows install in any way.

[monon]

Thank you, Schwarzer Kater, that fixed my issue. While I have you on the line, I have a laptop with Windows and Linux on the same disk. Would this Grub fix work on that, too?

To jlittle: I was having a problem in that if I even looked at the BIOS, the boot order would get changed to Windows first. Too picky, maybe, but I wanted to, as much as possible, separate Linux and Windows. The only reason I have Windows at all, is to use Turbo Tax.

[monon]

Schwarzer Kater: I am using UEFI to select the OS. Actually, if I do nothing the boot defaults to Linux, so I need to use UEFI only when I want Windows, which is seldom. Thank you, again.

[oshunluvr]

Thank you, Schwarzer Kater, that fixed my issue. While I have you on the line, I have a laptop with Windows and Linux on the same disk. Would this Grub fix work on that, too?

To jlittle: I was having a problem in that if I even looked at the BIOS, the boot order would get changed to Windows first. Too picky, maybe, but I wanted to, as much as possible, separate Linux and Windows. The only reason I have Windows at all, is to use Turbo Tax.

I suspect you missed jlittle's point. I believe his intent was to offer the idea that booting through BIOS at all is unnecessary because GRUB will allow you to boot to Windows whenever needed without invoking BIOS with the F2 or DEL key or whatever. Having the 2 operation systems on the same PC or even same drive doesn't somehow magically expose Linux to damage from Windows. Windows can't even access Linux file systems. The only possible downside is Windows does have a occasional bad habit of reinstalling it's boot loader. However, with the OSs on two different drives, that won't happen. Simply letting Windows only have access to one drive is sufficient to keep it isolated.

Frankly, if you really only use Windows for Turbo Tax why have it installed to bare metal at all? This is a perfect case for using a Virtual Machine, Then not only is Windows isolated it's also much more easily backed up and you would have snapshot capability of the Windows install.

[Schwarzer Kater]

Thank you, Schwarzer Kater, that fixed my issue. While I have you on the line, I have a laptop with Windows and Linux on the same disk. Would this Grub fix work on that, too? […]

If your laptop also has UEFI (and the drive has an corresponding partition scheme): yes.

But do consider what oshunluvr wrote.

[monon]

Hello, oshunluvr. Maybe you can teach an old dog new tricks. I have had the following problem at least twice, maybe more, with dual booting Linux and Windows: dual booting worked okay until it was necessary to do something in the system BIOS. After exiting the BIOS I was unable to boot Linux and had to resort to boot-repair to fix the problem. So I have been leery of making any changes or examinations of the BIOS. I am a good deal more comfortable with having to use the UEFI to load Windows, especially since I seldom use windows.

Your suggestion to use a Virtual Machine is a good one, but wouldn't I have to buy Windows to do that? If you know a way that I can obtain Windows or somehow use the Windows that is installed on my PC's, I am willing to listen. In any event thank you for ideas and input.

[claydoh]

I have to buy Windows to do that?

No, the worst that happens is that you have a somewhat restricted OS if it isn't activated.
https://windowsreport.com/windows-10...ut-activation/
I have a license that seems tied to one of my outlook email accounts that I have so far used across three different machines over a number of years, and even upgraded to Win 11 - without any issues activating it. I don't know how I managed that one, but it might be worth checking out:
https://www.makeuseof.com/link-windows-product-key-microsoft-account/

But I'd go with the unactivated Windows install in a VM for your purposes, myself. Or find any way to avoid using Turd-o tax.

[Schwarzer Kater]

[…] but wouldn't I have to buy Windows to do that? […]

Just use the Windows licence that came with the computer for the VM (but only if you use it in the VM and don't have to install it additionally in a separate partition/drive on the same computer) - at least this is what I had done at work for more than a dozen desktop installations that had to use a Windows VM within a Kubuntu system due to one specific program.
Worst case: you will have to phone the Microsoft robot to validate/activate the licence for the VM.

[jlittle]

Just use the Windows licence that came with the computer for the VM (but only if you use it in the VM and don't have to install it additionally in a separate partition/drive on the same computer) - at least this is what I had done at work for more than a dozen desktop installations ...

That's what I did at work for a couple of years. Having both OS running at the same time saves a huge amount of time, particularly when Windows wants to do one of it's long running updates. I followed some procedure google found to get the Windows product key; this was also good if I, or someone else (after I left), wanted to reinstall Windows to the metal.

I used qemu/kvm, again following some procedure google found. It was sufficiently simple and straightforward that I soon forgot the details (I wish I had documented it). Windows ran faster in the VM than it had done previously, once I gave it enough memory (6 GiB); I think this was because Windows on that laptop was long overdue for a reinstall. It was handy being able to move the VM around just by copying the files and a quick change to /etc/fstab. I moved it from the laptop's small NVMe drive to a SATA SSD and it still performed well.

After resisting valiantly for several years my work went all in with the Microsoft suite. (The web-based versions of Office were execrable, and Onedrive couldn't be trusted.) Suddenly I had to run several MS softwares in the VM and I had no trouble, though I didn't try anything using the laptop camera.

[monon]

First, to Scwarzer Kater: It appears that I have an EFI partition on the Windows disk, but not on the Linux disk. I am not sure what the implications of this are.

Also, it is not at all clear to me how I would find the microsoft license, or how I would use the software. The Windows software that I have came with the computers. I do not have any CD's or other type of media that contains software.

[Schwarzer Kater]

[…] Also, it is not at all clear to me how I would find the microsoft license, or how I would use the software. […]

Normally there is a sticker under or at the backside of the computer with the licence code.
To install Wíndows in a VM you can freely download an official ISO from Microsoft and use it with QEMU/KVM, VirtualBox or VMware Player.