Dualboot - Can't launch Windows 11 after installing Kubuntu 25.04 alongside it.

[Reding]

Here's another multi-boot problem.

I've solved that problem for myself several times before but this time I'm facing a dead wall.

Here's how my system looks like in Gparted. (See attached)

It's an absolute mess. Could someone assist me and show me how to have GRUB booting with Kubuntu and Windows listed in order to choose which OS I want to launch ?

Thanks so much in advance

Red

[Qqmike]

Windows ... well ... my friend ... there's always something!
You have experience with this, and so have you looked at things to see if the "pieces" are all there, like:
Both Windows and Kubuntu lisred in your UEFI/BIOS boot menus?
Examine exactly what is in the ESP: nvmen0n0p1? does it show boot folders for both Windows and Linux ("ubuntu' = Kubuntu)?
Is your GRUB menu set to show the GRUB menu of boot options upon re-booting your PC?

OK, so you may have heard that multiboots with Windows & Linux have been a problem, until MS issued their "fix":
Microsoft fixes Linux boot issues on dual-boot Windows systems
https://www.kubuntuforums.net/forum/...indows-systems

As you know, there's lots of issues to play with: secure boot, set SATA to AHCI, if using an SSD, etc., etc. ...

So, if it were me, I would FIRST relent and just try Boot-Repair to get clues and/or to actually fix it.

Boot-Repair
https://help.ubuntu.com/community/Boot-Repair

[oshunluvr]

The arrangement of your partitions is irrelevant to grub. It could be grub is not configured to look for other installs - that's the current default. You have to enable that.

Start by opening konsole, then;

PART ONE

Ensure 30_os-prober is enabled with this command: sudo chmod +x /etc/30_os-prober

Next, edit /etc/default/grub with this command: kate /etc/default/grub

Somewhere near line 18 you should see: #GRUB_DISABLE_OS_PROBER=false

Simply remove the # at the front of the line, but don't close Kate yet.


PART TWO

As far as the boot menu and being able to select easily between the two, this will likely require more edits to /etc/default/grub and may vary depending on your desired outcome.

While still in Kate with /etc/default/grub still open:

To make the boot menu always visible, change GRUB_TIMEOUT_STYLE=hidden to GRUB_TIMEOUT_STYLE=menu

To make Windows the default instead of Linux, change GRUB_DEFAULT=0 to GRUB_DEFAULT=2

To have your default choice boot automatically after a set amount of seconds, change GRUB_TIMEOUT=0 to GRUB_TIMEOUT=10

"10" means 10 seconds. Use whatever value you prefer. If you leave it zero, the menu will wait indefinitely for your selection.

Now save the file (Kate will ask for your password) and close Kate.

Now (still in Konsole) enter this to update grub: sudo update-grub

As the update runs, you should see a message "Found Windows bootloader" or something to that effect. If you do, you will see Windows in the grub menu at next boot.

[Qqmike]

I guess they haven't yet changed/fixed that os-prober issue.

Do you mean sudo update-grub?

[oshunluvr]

Thanks! Fixed!