Dual booting *from an other OS'es GRUB* into Qubes with Legacy BIOS

User Support General
1

I carefully evaluated my personal preferences, needs and threat model and decided that, when I boot, I want to come into the GRUB menu managed from an other OS than Qubes from which I can select all installed operating systems including Qubes. I read Multibooting Qubes but my answer wasn’t there because it is a guide for the other way around: Qubes manages the bootloading process and I can add manual boot entries to select in the from Qubes managed GRUB menu to boot into an other OS than Qubes.

I want it the other way around though: I can boot into a from an other OS managed GRUB menu and choose from there to boot into my main OS or to boot into Qubes this time.

The guide explains how to add manual boot entries for the from Qubes managed GRUB menu to boot into other OSes than Qubes and I want to know how to add manual boot entries for the not from Qubes managed GRUB menu because os-prober does not recognize Qubes as OS.

I already installed Qubes onto my SSD and selected the option “do not install bootloader” in the installation process.

I use a MBR-only, Legacy BIOS, no-UEFI machine.

I hope my question is understandable. If not, I can elaborate further, just ask.

2

If you have Qubes installed you probably have /etc/grub.d (in Qubes OS filesystem). Grub menu for Qubes is generated by /etc/grub.d/20_linux_xen. From there you could figure out analogous functionality for your primary system.

The file might be missing since you opted to not install bootloader. You can download the package from the repository and obtain 20_linux_xen that way.