Re: Code sharing between system and home services (was Re: On the naming of System and Home services modules.)

[Joshua Branson]

Xinglu Chen <public@yoctocell.xyz> writes:

> On Thu, Sep 23 2021, Ludovic Courtès wrote:
>
>> Hi,
>>
>> Xinglu Chen <public@yoctocell.xyz> skribis:
>>
>>> Some services might be useful to have in both Guix System and Guix Home;
>>> for instance, Guix System currently has a service for configuring
>>> Syncthing, and I think it makes sense to also have one for Guix Home,
>>> this would mean that people not using Guix System (me :-)) could also
>>> have Guix manage Syncthing.  With the current approach, we would have to
>>> copy and paste quite a bit of code, and if the Syncthing service for
>>> Guix System changes, then the one for Guix Home might have to change as
>>> well.
>>
>> Silly question, but why do we need to have two different configuration
>> record types in the first place?
>
> The problem is that the configuration records for system and home
> service don’t necessarily have the same fields.  The Syncthing service
> for Guix System has a ‘user’ and a ‘group’ field, which is not really of
> any use in Guix Home, as the only user would be the user invoking ‘guix
> home’.

Apologies if I'm speaking for something I know very little
about...Wouldn't it be nice if guix home services would accept a user
and a group field?  For the syncthing service, perhaps the user wants to
limit Syncthing's runtime permissions.  So instead of running as the
user, the user would run synthing as a different user with less permissions?

Please note it may be much better to just container-ize the synthing
service.  Does guix home have that ability?

https://guix.gnu.org/en/blog/2017/running-system-services-in-containers/

>
>> Sharing configuration between Home and System sounds important to me: it
>> means users can easily move services from one to the other, which is
>> pretty big deal.  It also means we’d have much less code to maintain.
>
> Agreed, that’s what I would like to see as well.
>
>> Would that be feasible?  (Apologies if this has already been
>> discussed!)
>
> Since it might not make sense to have the same records fields for a
> system service and home service, I proposed (in the mail you replied to)
> a ‘define-configuration’ form that would generate a configuration record
> for a system service and optionally one for a home service, without
> having to maintain two records separately.
>
> (define-configuration syncthing-configuration
>   (package
>    (package syncthing)
>    "Syncthing package to use.")
>   (arguments
>    (list-of-strings ’())
>    "Command line arguments to pass to the Syncthing package.")
>   (log-flags
>    (integer 0)
>    "Sum of logging flags.")
>   (user
>    (maybe-string 'disabled)
>    "The user as which the Syncthing service is to be run."
>    (home-service? #f))  ; not for Guix Home
>   (group
>    (string "users")
>    "The group as which the Syncthing service is to be run."
>    (home-service? #f))  ; likewise ^^
>   (home
>    (maybe-string 'disabled)
>    "Common configuration and data directory.")
>   (home-service? #t))
>
> It would generate <syncthing-configuration> and
> <home-syncthing-configuration>.  The only difference being that
> <home-syncthing-configuration> doesn’t have a ‘user’ and a ‘group’
> field.
>
> It’s probably going to be quite complicated, so it would be good to get
> some feedback/thoughts on it.  Cc Maxim since he has done some work with
> (gnu services configuration).
>
> Also, it’s probably time to properly document (gnu services
> configuration) in the manual.  ;-)
>
>> Also, I proposed earlier a possible way to generate a Home service type
>> from the corresponding System service type—or, IOW, to generate a Home
>> service type graph from the System graph.  Does that sound feasible?
>
> I am not sure exactly what you mean here, could you elaborate?
>

-- 
Joshua Branson (jab in #guix)
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