I’ve already spent two days trying it myself and found this forum post
about it (@bawdyanarchist, @metahertz):
https://forum.qubes-os.org/t/rescue-re-install-the-efi-and-boot-grub-initrahttps://forum.qubes-os.org/t/rescue-re-install-the-efi-and-boot-grub-initramfs-partitions/26210
So I followed their examples:
1 )
Make a bootable USB
Boot into the UEFI partition, and select
Rescue a Qubes OS system; then
3) Skip to shell
2 )
Enter passphrase for /dev/«rootpartition»: vgchange -ay qubes_dom0 mkdir /mnt/rescue mount /dev/qubes_dom0/root /mnt/rescue
mount /dev/«bootpartition» /mnt/rescue/boot mount /dev/«efipartition» /mnt/rescue/boot/efi mount --rbind /dev /mnt/rescue/dev mount --rbind /proc /mnt/rescue/proc mount --rbind /sys /mnt/rescue/sys
From this point onward, I encountered issue - my entire /boot/efi
directory was missing. To proceed, I used /etc/grub2.cfg (chrooted) and
reinstalled Qubes on a separate hard drive. There, I copied the
grubx64.efi and xen-4.17.5.efi files. As the first responder in the
above forum post already explained, I then mounted the partition, moved
the EFI files to the EFI/qubes directory, and executed the following
commands:
efibootmgr -v -c -u -L QubesOS -l /EFI/qubes/grubx64.efi -d /dev/nvme0n1 -p 1 chroot /mnt/rescue grub2-mkconfig -o /boot/efi/EFI/qubes/grub.cfg
Once I had unmounted everything and accessed the extended boot menu to try
booting Qubes, QubesOS was actually listed there! However, when I
attempted to start it, I was immediately sent back to the menu. Do you
have any ideas about what I might have done wrong and how I could resolve
this issue?
Thank you for your help and support,
Schnur.