Dual-booting solution with only one actual Grub installation

[Thorsten Wilms]

Hi once again,

There's a convenient dual-booting solution that I think hasn't been 
mentioned in these circles. You can let Grub2 offer an item that will 
load another grub.cfg.

In my case, that's a Grub installed from Ubuntu, with a menu that will 
be updated in sync with kernel installation/removal, plus one "Guix SD" 
item that will lead to the known Guix SD menu, also always up-to-date, 
without an actual second Grub installation.

No manual updating, no chain-loading of one or the other from an 
independent third Grub.

Guix SD: /etc/config.scm, in operating-system:
----
(bootloader (bootloader-configuration (bootloader (bootloader (inherit 
grub-bootloader) (installer #~(const #t))))))
----

Thanks to snape in #guix. With this, /boot/grub/grub.cfg will be 
generated, but Grub won't actually be installed.


Other system with Grub in MBR, addition to: /etc/grub.d/40_custom:
----
menuentry 'GuixSD' {
  search --fs-uuid --set=root a3a97a6f-a4c9-4569-98a3-4306f4db9ff8
  configfile /boot/grub/grub.cfg
}
----
Don't forget `sudo update-grub`.

--
Thorsten Wilms

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