Re: Customizing /etc

[Alex Kost <alezost@gmail.com>]

Ludovic Courtès (2016-09-19 23:08 +0900) wrote:

> Alex Kost <alezost@gmail.com> skribis:
>
>> Ludovic Courtès (2016-09-14 16:58 +0200) wrote:
[...]
>>> However, we failed to build consensus around the approach of this patch,
>>> so we did not apply it.  If you have ideas, please email
>>> 20255@debbugs.gnu.org.  :-)
>>
>> I think I was the one who prevents the consensus.  To make it clear, I'm
>> for the suggested solution, but only *after* giving a user a freedom to
>> avoid loading such a heavy command as "guix package --search-paths".  On
>> a "usual" GNU/Linux distro a user can edit /etc/profile, but on GuixSD
>> it is not possible currently.  That's why I think there should be
>> provided a possibility to override /etc/profile at first.
>
> Indeed, thanks for the reminder!
>
> In fact, we have this through ‘etc-service-type’, except that currently
> /etc/profile is systematically added.
>
> So an idea that comes to mind is to allow ‘etc-service-type’ to be
> extended with procedures that would be able to filter or otherwise
> change the /etc entries (similar to what we do for PAM):
>
> diff --git a/gnu/services.scm b/gnu/services.scm
> index 7e322c5..9397232 100644
> --- a/gnu/services.scm
> +++ b/gnu/services.scm
> @@ -426,9 +426,13 @@ directory."
>                  (extensions
>                   (list
>                    (service-extension activation-service-type
> -                                     (lambda (files)
> -                                       (let ((etc
> -                                              (files->etc-directory files)))
> +                                     (lambda (files+procs)
> +                                       (let* ((proc (apply compose
> +                                                           (filter procedure?
> +                                                                   files+procs)))
> +                                              (files (filter pair? files+procs))
> +                                              (etc
> +                                               (files->etc-directory (proc files))))
>                                           #~(activate-etc #$etc))))
>                    (service-extension system-service-type etc-entry)))
>                  (compose concatenate)
>
>
> In your config, you could have something like:
>
>   (services (cons (simple-service 'rm-/etc/profile etc-service-type
>                                   (const (lambda (files)
>                                            (assoc-delete "profile" files))))
>                   %base-services))
>
> WDYT?

I think it would be great!  I didn't realize it can be implemented this
way.

> In fact I think we would need to have a more generic mechanism to hook
> into ‘fold-services’, but I’m not sure what it should look like.

Yeah, a more generic way would be better of course, but I think this
mixing of files and procedures is already good enough for now, as it
provides a freedom in customizing a system that we didn't have before.
Besides I will no longer object against the "search-paths" fix for the
bug 20255 :-)

-- 
Alex