[bug#27521] [PATCH v5] build: Add iso9660 system image generator.

[Danny Milosavljevic]

Hi Ludo,

> Let’s add #:key (volume-id "GuixSD") and then:
> 
>   "--" "-volid" (string-upcase volume-id)

It will fail when booting from CD because GuixSD can't find the root fs.

> Since this doesn’t have much to do with VMs, what about adding these
> things to (gnu system iso9660) and (gnu build iso9660)?

I'd be fine with it but I think adding it to system-disk-image (as this patch 
does) is actually quite fitting - also, most of the stuff in there is not for 
VMs either.  There are comments all over system-disk-image how it makes sure 
not to set up the stuff for qemu but for real hardware.

> We can also remove this ‘if’: it’s not natural for ‘qemu-image’ to
> produce something that’s not a “QEMU image.”

The patch context is misleading :)

What it actually does is extend system-disk-image:

(define (system-disk-image ... file-system-type)
  ...
  (if (= file-system-type "iso9660")
      (iso9660-image ...)
      (qemu-image)))

And if we want we could actually drop the entire non-iso9660 hydra image (after 
testing, of course) because the grub-mkrescue image will boot from usb stick as 
well.  So no need to have two different ones, actually.

> Could you update “Invoking guix system” accordingly?

We could replace the old "guix system disk-image" by a new "guix system 
disk-image" which always creates the iso9660 image.

Or are there other use cases of "guix system disk-image" ?