How does install-grub work?

[Danny Milosavljevic <dannym@scratchpost.org>]

On Mon, 29 Aug 2016 20:20:30 +0200
David Craven <david@craven.ch> wrote:

> > Note: It should infer the correct u-boot to use on its own - at least that's the intention with the whole make-u-boot-package thing.  
> 
> Did you see the updated u-boot patch? It includes support for
> cross-compilation,

Nice!

> so make-u-boot-package takes a xgcc package and a
> target triplet as arguments. So it probably broke the inference.

No, I think I didn't make it work yet.

I've modeled along the lines of what was already there for Grub. But I've got no idea where gnu/build/install.scm's install-grub finds "grub-install" - so the u-boot part doesn't work either since I don't know where to put the package reference in the first place (or how in the world it works for Grub to begin with).

Also, there's a few mysterious things with install-grub.

For example the documentation in the function header there says

  "Install Grub with GRUB.CFG on DEVICE, which is assumed to be
mounted on MOUNT-POINT."

I really doubt that it actually does what it says since usually grub is installed on the drive MBR and not inside a partition. And MOUNT-POINT is a mounted filesystem on a partition, right? So the whole drive is certainly not mounted at MOUNT-POINT.

MOUNT-POINT originally comes from guix/scripts/system.scm - process-action. And that is called by process-command. And that is called by guix-system which is used when invoking "guix system" "reconfigure". But I've never specified a mountpoint when invoking that...