Re: 20/36: system: hurd: Add the Shepherd.

[Jan Nieuwenhuizen <janneke@gnu.org>]

Ludovic Courtès writes:

Hi Ludo'!

>> commit bb17242a511014e1691d494b17152865db0580e0
>> Author: Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
>> AuthorDate: Tue Apr 7 08:03:03 2020 +0200
>>
>>     system: hurd: Add the Shepherd.

>> +  (define shepherd.conf
>> +    (with-parameters ((%current-target-system "i586-pc-gnu"))
>> +      (shepherd-configuration-file (hurd-shepherd-services %hurd-os))))
>
> This looks like an intermediate before fully using the service/OS
> framework

TL;DR: Thanks a lot for your review and questions!  I will be using this
to rewrite the Shepherd/services introduction in a proper way, until
it can be merged.

> , but I wonder how much it helps.

Yes, that's exactly it!  This intermediate, is curerently the only way I
found that can produce a fully functional VM-image; i.e., one that
starts guix-daemon and openssh.  So it helps by being an intermediate.

> The way I see it, now that you’ve defined services for Hurd-specific
> things like the console client, you could very much write:
>
>   (operating-system
>     ;; …
>     (kernel gnumach)
>     (hurd hurd)  ;<- we probably need this new field

(oh...prolly better than the (if hurd-target?) I've been sprinkling and
implicit adding of gnumach.  I'll have a go at this.

>     (essential-services (hurd-essential-services this-operating-system))
>     (services %base-hurd-services))
>
> (Eventually we can even arrange for ‘essential-services’ and ‘services’
> to pick the right default as a function of the chosen kernel.)
>
> and then do:
>
>   guix system build --target=i586-pc-gnu the-config-above.scm

> Assuming system cross-compilation works as advertised :-), it should
> cross-compile the whole system.

Yeah...is seems that the marketing department may have sold us something
that has yet to be delivered.  Either that, or I failed to read some
bits of the instruction manual ;-)

To get something to run, we need (near the top of wip-hurd-vm)

    6302837257 HACK Don't fail on running host's localedef.
    443e1b2176 gnu: hurd: Cross-build hack: Set target i586-pc-gnu if unset.
    87b50146ee gnu: glibc/hurd-headers: Cross-build fix for the Hurd.

So, on a well-chosen version of wip-hurd-vm (for example: wip-hurd-vm24
on my gitlab), I can now finally run this

    ./pre-inst-env guix system build --target=i586-pc-gnu gnu/system/examples/bare-hurd.tmpl

...but (most of) the OS is not cross-compiled; <profile>/bin/bash is the
build host's bash.  Some things, like Grub, Gnumach, the Hurd are cross
compiled, so ...

> At that stage, you don’t need ‘cross-hurd-image’ any longer and you can
> instead run:
>
>   guix system vm-image --target=i586-pc-gnu the-config-above.scm
>
> to achieve the same result.

... indeed, running:

    ./pre-inst-env guix system vm-image --target=i586-pc-gnu gnu/system/examples/bare-hurd.tmpl

creates a bootable VM-image that drops into a bash-minimal shell,
because <profile>/bin/bash cannot be executed.

> But!  There’s one missing bit: a Hurdish grub.cfg.  I think that can be
> hacked in (gnu bootloader grub), by inheriting from ‘grub-bootloader’
> and providing a custom ‘configuration-file-generator’ field and maybe
> ‘installer’ as well.

I think I have that covered here

    d6ec2c2543 * system: hurd: Add hurd-grub-configuration-file.
    a9a6b716d9 * system: hurd: Add hurd-grub-minimal-bootloader.

possibly depending on these

    4fd4296325 * system: Add hurd-operating-system-directory-base-entries.
    f4f872a440 * services: hurd: Move hurd-default-essential-services.
    5f7c73d83a * services: Add hurd-file-systems-service-type.
    d7cd2f122d * services: hurd: Move hurd-etc-sevcices.

> Thus, (gnu system hurd) would be left with nothing but the definitions
> of ‘%base-services/hurd’, ‘%base-packages/hurd’, and so on.
> ‘hurd-essential-services’ could maybe go to (gnu services hurd).

Yes!

> But I wonder if I’m missing something, WDYT?

You're right...and this is what I am trying to work towards.  The reason
for me to introduce these intermediate steps is that they enable to run
intermediate tests.

Currently, "guix build -f gnu/system/hurd.scm" is the only way I have
that produces a functional VM.  We are pretty close t creating such a
thing with "guix system ...", but to do so we need a cross build that
works and a shepherd config generated...and that all needs to come
together.  So instead of attempting a giant leap, I'm trying to throw
some intermediate stepping stones in the pond :-)

We don't need to merge, or keep this history; but I don't see how to
walk this path without going round these extra curves; let alone getting
feedback or asking questions.  So I can imagine that these commits keep
being rewritten/removed on wip-hurd-vm until everything works.

> Thanks for the exciting developments again!  :-)

Thanks for your insights, we're getting there...  I have some more
specific, related questions/puzzles in response to your other mail about
services.

Greetings,
janneke

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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