Dual Boot with windows while qubes os is already installes

User Support
1

I searched and only found posts regarding dual booting while installing windows first but i want to do the opposite,I already have qubes os installed, i have a 1tb ssd with qubes partitions occupaying like 300 gb and 1 ntfs 650gb empty partition ready for windows, I already got the windows installation usb ready too, the problem here is that im a bit newbie but i know grub will be overwritten with windows boot manager and im scared to go back and forth configuring it and then i lose access to qubes os and having to install it again

2

Did you install Qubes OS in UEFI or Legacy mode?

3

Uefi

4

Uefi mode

5

Then Windows won’t overwrite the GRUB.
You can just install Windows normally, it should reuse the existing EFI System partition and it’ll just add the WIndows UEFI boot entry in addition to Qubes OS entry.
You can select which entry to boot in your UEFI Boot manager.

6

Are you sure cause i did it before and grub completely disappeared and i havent touched any of those partitions.
Just to make it clear i got
Nvme0n1p1 - 630gb ntfs (empty
Nvme0n1p2 - /boot/efi 600mb
Nvme0n1p3 - /boot 1024mb
Nvme0n1p4 - luks 250gb

If i install windows on p1 i wont have any issue with booting into both systems?

7

I don’t remember how WIndows installer works by default so I can’t tell for sure.
In the Windows installer you need to make sure that Windows won’t reformat the existing EFI System partition and reuse it instead.
Also maybe you’ll need to restore the Qubes OS EFI boot entry if it’ll be removed for some reason like this:

8

Thank you mate!
Any idea on how i can make sure windows wont reformat the existing qubes partition and reuse it?
Because in windows instal i just select the nvme0n1pq and install it and nothing else

9

I guess it should be the same as for any other Linux+Windows dual boot:
https://wiki.archlinux.org/title/Dual_boot_with_Windows#Linux_before_Windows

10

Well a little update, im f*cked
Windows is installed and boots fine trough windows boot manager but in the meanwhile when i change the boot priority to be able to boot qubes os it boots a black screen…
My work depends on qubes… Any help someone? Please im lost af, i still have the usb from instalation i can boot into rescue mode but i have no idea what to do

11

Do you see the GRUB menu when you boot the Qubes OS UEFI menu entry?
Check the files in EFI System partition to see that Qubes OS boot files are still there in EFI/qubes/ directory. I think you can check this in WIndows.
Boot from some Live Linux OS (e.g. from Qubes OS installer and switch to the console with Ctrl+Alt+F2) and check if your Qubes OS partitions are untoched:

fdisk -l