Qubes 4.2 Windows multiboot no longer works

When I first moved from Linux Mint to Qubes, I first saved the grub configuration I had.

I installed Qubes (didn’t have Windows option), added the Windows option to grub, unt voila, I could boot into Windows (if I wanted to play games) or Qubes (for everything else).

When I re-installed Qubes (now 4.2, which gave me its own set of problems, now solved, see Qubes 4.2 installation fails at networking). I thought, okay, I’ll just modify grub and get my Windows bootable again. So I added the following to /etc/grub/40_custom:

menuentry 'Windows 10 (on /dev/sdb1)' --class windows --class os $menuentry_id_option 'osprober-chain-ABCDEF0123456789' {
	insmod part_msdos
	insmod ntfs
	set root='hd1,msdos1'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,msdos1 --hint-efi=hd1,msdos1 --hint-baremetal=ahci1,msdos1  ABCDEF0123456789
	  search --no-floppy --fs-uuid --set=root ABCDEF0123456789
	parttool ${root} hidden-
	drivemap -s (hd0) ${root}
	chainloader +1

(I’ve anonymised the ABCDEF0123456789 numbers just in case)

And regenerated grub with grub2-mkconfig -o /boot/grub2/grub.cfg.

This time however, when I reboot, I see the Windows 10 option (hoorays), but when I try boot, I get this:

error: file `/grub2/x86_64-efi/ntldr.mod' not found.
error: file `/grub2/x86_64-efi/ntfs.mod' not found.
error: can't find command `ntldr'.

Looking at /dev/sdb1, those are the files that are in there (ntldr.mod, ntfs.mod don’t exist).

I’m not really sure what to do. Those files are clearly DOS type files, (not Linux type). This used to work with the old Qubes but not this.

Any ideas how to fix?


Not sure but maybe it should be hd1 here as well?

Well, the problem was what I feared.

Windows had clearly been installed using non-UEFI, and when I installed Qubes-OS I used UEFI. The fix, was to re-install Qubes-OS, but this time selecting the non-UEFI option when I booted from the USB stick.

Having done that, modifying the grub2 config as described in the original post, it all works. Can choose to boot into Windows, or into Qubes-OS.