Mathieu Othacehe writes:

Hello Mathieu!

>> The conclusion here is that, I think that we very few adaptations to
>> your branch, we should be able to produce Hurd ISO images or Hurd EFI
>> compatible disk-images. Maybe it would be a first step.
>>
>> Then, we could find a way to create "MBR compatible" Hurd and Linux
>> disk-images in (gnu system image).
>
> Ok, I made further progress. Turns out the Hurd EFI solution was a
> dead-end, because I have a "no console will be available to os" message
> in Qemu, instead of Hurd console output. I don't feel like debugging
> this.

Ah, well that's the only result that I also came up with and wanted to
share.  Maybe Ludo has an idea how to fix that; I could not find
anything helpful yet.

> So, back to the MBR solution. I had another look to what OpenWrt is
> doing. They found a really nice work-around! As I stated, we cannot use
> "grub-install", but this command is in reality a wrapper around
> "grub-mkimage" and "grub-bios-setup".

Ah!  That's good to know.

> #######################################
> #     #            #                  #
> # MBR # MBR-GAP    # FIRST PARTITION  #
> #     #            #                  #
> #######################################
>
>
> grub-mkimage generates a Grub image, small enough so that it can fit in
> the MBR-GAP (the space between the MBR and the first partition).

Okay...

> It cannot contain all Grub modules, but that's not an issue, because
> Grub will be able to find missing modules from the first partition when
> started.

aha...

> They also patched grub-bios-setup[1] so that it can work on a raw
> disk-image, and install the previously generated "grub.img".

So, this is one aspect of what we're avoiding by running grub-install
in a qemu vm, right?  Any idea on the upstream status of this patch?
(I don't think it matters all that much for us, let's use it :-)

> So with the following commands:
>
> grub-mkimage -O i386-pc -o core.img  biosdisk part_msdos ext2
> echo "(hd0) /tmp/my-disk-image" > device.map
> grub-bios-setup -m device.map -r "hd0,msdos1" -d tmp /tmp/qemu-image2
>
> I'm able to make a Guix system image bootable, without root
> permissions. It then starts the Hurd kernel and crashes, but that's
> another story :p

Thats *great*, no really!

> So, if it's ok for you, I can integrate this stuff cleanly, and we won't
> need the vm-image stuff anymore.
>
> WDYT?

That seems a very good idea, I'm cc'ing Ludo to ping him about this.

I'm attaching some hacky work that I did on the patch that you paste'd
to me via IRC, adding som Hurd'y things.  Maybe the pointers are
helpful, but it's all pretty obvious.

Greetings,
Janneke

> [1]:
> https://github.com/openwrt/openwrt/blob/master/package/boot/grub2/patches/100-grub_setup_root.patch