@letizido-0 I solved my own problem. It turns out grub-mkconfig reads every file in the /etc/grub.d/ directory and builds the grub.cfg trying to include everything. Much easier to just directly edit the grub.cfg and add the menu item with proper settings. Working fine now. Perhaps you may want to look at all those scripts in /etc/grub.d/ and remove what XCP-ng doesn't use/need.

Hello,

This is a somewhat strange request, but I figured I would post it anyway in case someone else has my use case.

I installed XCP-ng 8.3 RC2 on two hosts. On my newer host, I have 96G ram, a 1T and a 4T drive. I have already deployed a few VMs (Windows 11 and various flavors of Linux. Everything is running well. No complaints. I also am running Xen Orchestra from source on a separate machine as a container. All good so far.

Now for my use case: The newer host has a CPU/GPU chip combo powerful enough to run medium-complexity games on, but I don't believe the Windows VM has enough access to the GPU to run the games at their full rendition. So, since this is a lab/play installation anyway, I wanted to explore the potential of installing Windows 11 on the 4T drive to dual boot between XCP-ng and Windows 11. I have already installed Windows no problem on the 4T drive and it is bootable from the EFI boot menu. What I really want to accomplish is to get the Windows boot menu item into the XCP-ng grub menu so that I don't have to use a keyboard interrupt to bring up the EFI boot menu. I have tried several times to modify grub to add the Windows menu item, but every time I try it I get a corrupt grub menu. Any ideas?

I have modified the /etc/grub.d/40_custom file, adding the following to the end of the file:
menuentry "Windows 11" {
set root=(hd0,2)
chainloader +1
}

I then ran the following to modify the grub.cfg in /boot/efi/EFI/xenserver/
grub-mkconfig -o /boot/efi/EFI/xenserver/grub.cfg

When I reboot, the menu appears as all special characters, and does boot up xcp-ng. I can then log in as root and revert to the original grub.cfg and all is well. It's just that the menu is corrupt.

Has anyone tried this and succeeded? I would appreciate it if you could reply to this post.