[Post-Install] Going from Clean Install to a Kubuntu & Windows 10 Dual Boot

[Punk Solar]

So I have had a great experience with gaming on Ubuntu/Kubuntu so far, the one or two extra set up steps I need for certain games was worth the significant quality of life improvement compared to Windows. However, I have learned that my VR headset, the Vive Cosmos does not have native drivers, and there is no clean, well-documented approach to third-party setup.
I tried several methods and found no luck, because they simply weren't built for running on Linux.
So I want to set up a dual boot for Windows 10, so I can run my VR games natively and any other software I want/need to use that simply doesn't have any safe or reliable workaround for running on Kubuntu.
Problem is, all the dual booting guides I find are about going from a Windows 10 set up to a Linux/Windows dual-boot, where as I need help with the opposite approach: A clean install of Kubuntu to a Kubuntu - Windows 10 Dual Boot.
What is the recommended way of setting up a Windows 10 dual-boot partition from Kubuntu?

I have already made a Windows 10 installation USB via Ventoy, what I need help with now is what are the appropriate steps of preparing for installing that disk image.

Edit: For future reference I should clarify: I have four hard drives installed in my build, 3 of them are solid states, so I have options for where to install the Windows 10 OS

[oshunluvr]

Assuming EFI, you should just have to have a partition for Windows and install to it. The installer will find the EFI partition and use it.

The key will be to not let Windows use the whole disk. That's where people mess up. If it were me, I would backup anything you don't to lose just in case.

Steps:

• Create space on your the drive and a new partition.
  • If Kubuntu occupies the entire drive, you will need to shrink an existing partition.
• Boot the Windows installer and specify the new, empty partition as the install location.
• Once installed, reboot to the Windows install and update.

At this point, only Windows will be bootable because it will over-write the GRUB boot manager on the drive - this is why everyone installs Windows first.

In some cases, with two EFI entries, your BIOS may let you select Linux from a boot menu. If so, boot to Kubuntu and re-install GRUB or just use the BIOS to choose every time you boot.

To re-install GRUB, boot to a live USB Linux. You now have a couple ways to re-install GRUB from a live session but to me, using the live session to boot to the existing Kubuntu install (not the live USB) is the easiest. From the live session GRUB menu, edit the boot stanza to point to the installed version of Linux. Or enter the GRUB console and manually enter the installed partition, kernel, and initramfs. Once you have booted into Kubuntu on your drive, reinstall GRUB.

Alternately, you can boot to the live session, then use the chroot method to install GRUB for your drive. This one to me, is easiest to mess up.

All of these methods work. It's up to you to pick which one is to your liking, There are tutorials all over explaining how to do any of these.

[oshunluvr]

Here's the chroot method assuming Kubuntu is installed to /dev/sda2:

Mount the Linux Partition:
sudo mount /dev/sda2 /mnt

Mount Essential Directories:
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys

Chroot into Linux:
sudo chroot /mnt

Reinstall GRUB:
sudo grub-install /dev/sda

Update GRUB configuration:
sudo update-grub

Exit Chroot and reboot:
exit
reboot

You should now get the GRUB menu and be able to boot Kubuntu. Once your back in Kubuntu, you'll need to enable the GRUB os_prober and update GRUB again to put Windows into your GRUB menu.

[Punk Solar]

Assuming EFI, you should just have to have a partition for Windows and install to it. The installer will find the EFI partition and use it.

The key will be to not let Windows use the whole disk. That's where people mess up. If it were me, I would backup anything you don't to lose just in case.

Steps:

• Create space on your the drive and a new partition.
  • If Kubuntu occupies the entire drive, you will need to shrink an existing partition.
• Boot the Windows installer and specify the new, empty partition as the install location.
• Once installed, reboot to the Windows install and update.

At this point, only Windows will be bootable because it will over-write the GRUB boot manager on the drive - this is why everyone installs Windows first.

In some cases, with two EFI entries, your BIOS may let you select Linux from a boot menu. If so, boot to Kubuntu and re-install GRUB or just use the BIOS to choose every time you boot.

To re-install GRUB, boot to a live USB Linux. You now have a couple ways to re-install GRUB from a live session but to me, using the live session to boot to the existing Kubuntu install (not the live USB) is the easiest. From the live session GRUB menu, edit the boot stanza to point to the installed version of Linux. Or enter the GRUB console and manually enter the installed partition, kernel, and initramfs. Once you have booted into Kubuntu on your drive, reinstall GRUB.

Alternately, you can boot to the live session, then use the chroot method to install GRUB for your drive. This one to me, is easiest to mess up.

All of these methods work. It's up to you to pick which one is to your liking, There are tutorials all over explaining how to do any of these.

Kubuntu is taking up my whole boot disk, but I have multiple hard disks, including a smaller SSD that I could free up for setting up the Windows 10 partition onto. Seeing I have the option to have Windows 10 installed on a separate disk from the main SSD that Kubuntu runs on, would it be better for me to install Windows 10 on that disk so all the Windows 10 stuff is contained on its own drive, or should I still shrink my Kubuntu root partition to install Windows 10 on the same disk?

My root partition is mounted /dev/sda2 by the way.

[claydoh]

Ok, my real-world experience installing WIndows 11 on the same drive as my Linux desktop, done in February.
The OS should not matter here, but mine is KDE non, so Ubuntu 24.04 is the core OS here.

I used a live desktop session of Kubuntu 25.10 for no particular reason, to run KDE Partition Manager, shrinking down my Linux partition. I used ~80Gb, but you want at least 50, at the most bare minimum. Windows will take close to 50. For my purpose, 80 was too small (that ONE game that runs like crap on Steam with an Arc GPU is ginormous. darn it!). My Windows install with FF, Chrome, drivers, and maybe a utility or two is just under 50. I had to use space on another drive for my Steam folder, so that 50 does not include any games. So resize using as much space as you can afford.

Reboot to the Windows installer. As mentioned previously, select that empty space you have made.

You will need to reset your boot order in your BIOS after completing WIndows install and setup.

I did NOT lose my Linux bootloader at all. On EFI systems, each OS has its own separate bootloader. SO you just need to set Kuubntu as the first boot option, so you get a boot menu, else use your PC's F-key for one-time boot selections. Mine is F8, but this varies by brand of PC or motherboard.

Now, after all this, and booting to Kubuntu you will want to enable the os-prober in Grub, and update grub so that Kubuntu can add WIndows to its menu.

After some bigger WIndows updates, your system might have the boot order reset, so you may once in a while need to reset this in the bios. I have not seen that yet on this machine, it has been two months since I installed Windows here, and I seldom boot it. On my older HP and Windows 10, it happened a number of times over a few years.


I was somewhat afraid that Windows might format the EFI partition even though research seems to indicate that it would not, and was prepared for that, but it did not happen.

[Qqmike]

If you need this:

A hassle, but os-prober is not enabled by default.
So,

To enable os-prober in Kubuntu (so GRUB can detect other operating systems (like Windows) in the GRUB boot menu), you must edit the GRUB configuration file:
set GRUB_DISABLE_OS_PROBER=false, and then update GRUB.
Details:
Open the GRUB configuration file /etc/default/grub
Add (or uncomment by removing #) the following line:
GRUB_DISABLE_OS_PROBER=false
Save and Exit
Update GRUB: Run sudo update-grub
Reboot: Restart your computer to see the updated menu