Re: Image generation

["Ludovic Courtès" <ludo@gnu.org>]

Howdy!

Mathieu Othacehe <m.othacehe@gmail.com> skribis:

> I made some progress on the image generation topic. As discussed
> previously, the goal is to use the same principles as genimage[1], to
> achieve faster image generation, without resorting to VM.

Awesome.

> A very related topic, is to bring the possibility to create Guix System
> images with custom layouts. That includes position, size and type of the
> bootloader partition, offset of the root partition and so on. While this
> is not really important for desktop usage, it is almost mandatory for
> embedded usage.
>
> The wip-disk-image branch allows to define a Guix System image along the
> lines of:
>
> (define my-image
>   (image
>    (format 'disk-image)
>    (operating-system my-os)
>    (partitions
>     (list (partition
>            (size (* 40 (expt 2 20)))
>            (label "GNU-ESP")
>            (file-system "vfat")
>            (flags '(esp))
>            (initializer (gexp initialize-efi-partition)))
>           (partition
>            (size 'guess)
>            (label "Guix_image")
>            (file-system "ext4")
>            (flags '(boot))
>            (initializer (gexp initialize-root-partition)))))))

That’s really cool!  I’ve been willing to have something like that
forever, but the current <partition> record is buried on the build side,
which makes it inconvenient to use like you do above.

> On this branch, it is already possible to generate an EFI disk-image,
> with the traditional command:
>
> ./pre-inst-env guix system disk-image gnu/system/examples/desktop.tmpl
>
> On my computer, this takes 6m50 versus 2h30 for the master version. I
> tested the image in QEMU, everything seems fine.

Oh, this much on ‘master’?  Anyway, the speedup is undoubtedly there and
it’s really great.

> Now there's still plenty of work. This branch needs some more
> cleaning. Then we need to:
>
> * Add support for ISO images.

I see you did that in the meantime.

> * Extend support to grub (non-efi), extlinux and u-boot bootloaders.
> * Check everything works with --system and --target arguments.

Yeah.

I saw your message to janneke, and indeed, I think there’s room for
cooperation: janneke has come up with something that’s very close to
“normal” Guix System for GNU/Hurd, and one of the main stumbling blocks
in my mind is building the image and in particular getting proper GRUB
suppotr for multiboot OSes.

> I've re-implemented some parts of genimage in (gnu build disk-image)
> module. Now, we could also go further and remove the use of this tool
> completely.

I think it’s great.  :-)

Please do ping us when you want a closer review!

Ludo’.