Defining custom services in /etc/config.scm

Defining custom services in /etc/config.scm

[Sergiu Ivanov]

Hello,

I'm trying to start redshift [0] as a shepherd service, and this is how
I defined the redshift service in my /etc/config.scm:

(define evry-geolocation "48.63681:2.42777")
(define redshift-service
  (shepherd-service
   (provision '(redshift))
   (requirement '(xorg-server))
   (documentation "Start Redshift as a service")
   (start #~(make-forkexec-constructor
	     `("redshift" "-l" ,evry-geolocation)))
   (stop #~(make-kill-destructor))))

However, I can't find a way to add this to the services field of the
operating-system declaration.

When I try:

 (services (append
	    (list redshift-service
		  (service xfce-desktop-service-type)
		  (set-xorg-configuration
		   (xorg-configuration (keyboard-layout keyboard-layout))))
	    %desktop-services))

I get the message "Wrong type argument #<<shepherd-service> ...".

I understand that I should somehow construct a <service> (?) from my
<shepherd-service>, but I don't see a way to do it.

I've also seen a couple mailing list discussions [1,2] and a blog post
[3] about doing what I want in "pure shepherd", i.e. independently of
Guix, but these solutions seem to be doing more than what I need.

How can I add a custom shepherd service to the operating-system
definition in /etc/config.scm?

-
Sergiu

[0] http://jonls.dk/redshift/
[1] https://lists.gnu.org/archive/html/guix-devel/2018-02/msg00047.html
[2] https://www.mail-archive.com/guix-devel@gnu.org/msg46278.html
[3] https://guix.gnu.org/blog/2020/gnu-shepherd-user-services/

Re: Defining custom services in /etc/config.scm

[Ekaitz Zarraga]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, January 24, 2021 8:09 PM, Sergiu Ivanov <sivanov@colimite.fr> wrote:

> Hello,
>
> I'm trying to start redshift [0] as a shepherd service, and this is how
> I defined the redshift service in my /etc/config.scm:
>
> (define evry-geolocation "48.63681:2.42777")
> (define redshift-service
> (shepherd-service
> (provision '(redshift))
> (requirement '(xorg-server))
> (documentation "Start Redshift as a service")
> (start #~(make-forkexec-constructor
> `("redshift" "-l" ,evry-geolocation)))
> (stop #~(make-kill-destructor))))
>
> However, I can't find a way to add this to the services field of the
> operating-system declaration.
>
> When I try:
>
> (services (append
> (list redshift-service
> (service xfce-desktop-service-type)
> (set-xorg-configuration
> (xorg-configuration (keyboard-layout keyboard-layout))))
> %desktop-services))
>
> I get the message "Wrong type argument #<<shepherd-service> ...".
>
> I understand that I should somehow construct a <service> (?) from my
> <shepherd-service>, but I don't see a way to do it.
>
> I've also seen a couple mailing list discussions [1,2] and a blog post
> [3] about doing what I want in "pure shepherd", i.e. independently of
> Guix, but these solutions seem to be doing more than what I need.
>
> How can I add a custom shepherd service to the operating-system
> definition in /etc/config.scm?
>
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Sergiu
>
> [0] http://jonls.dk/redshift/
> [1] https://lists.gnu.org/archive/html/guix-devel/2018-02/msg00047.html
> [2] https://www.mail-archive.com/guix-devel@gnu.org/msg46278.html
> [3] https://guix.gnu.org/blog/2020/gnu-shepherd-user-services/





Hi Sergiu,

I recently made my redshift configuration using shepherd user
services, which is what people in IRC recommended me.

You can find it here:
https://github.com/ekaitz-zarraga/dotfiles/tree/guix/shepherd/shepherd

Also, it forces me to run the shepherd as a user using my i3 config.

I also wanted to configure it in my config.scm file but people
convinced me not to do so.

I'm not sure why your case shouldn't work though.

Best,
Ekaitz

Re: Defining custom services in /etc/config.scm

[Sergiu Ivanov]

Hi Ekaitz,

Thank you for your very fast answer!


Thus quoth  Ekaitz Zarraga  on Sun Jan 24 2021 at 20:19 (+0100):
>
> I recently made my redshift configuration using shepherd user
> services, which is what people in IRC recommended me.
>
> You can find it here:
> https://github.com/ekaitz-zarraga/dotfiles/tree/guix/shepherd/shepherd

I see, this is what I saw here as well
https://guix.gnu.org/blog/2020/gnu-shepherd-user-services/ , but
I didn't know whether I should prefer this solution over
other possibilities.

> Also, it forces me to run the shepherd as a user using my i3 config.

OK, so I note that I'll have to include shepherd in my startup scripts.

> I also wanted to configure it in my config.scm file but people
> convinced me not to do so.

Ah, interesting, good to know.  Thank you for the feedback!

> I'm not sure why your case shouldn't work though.

Maybe somebody here will have the time to explain the details, but for
the time being I will go with your solution, as it has the benediction
of the IRC herd :-)

-
Sergiu


> Best,
> Ekaitz

Re: Defining custom services in /etc/config.scm

[Carlo Zancanaro]

Hi Sergiu!

On Mon, Jan 25 2021, Sergiu Ivanov wrote:
> I understand that I should somehow construct a <service> (?) 
> from my <shepherd-service>, but I don't see a way to do it.

Unfortunately Guix overloads the word "service", where we have (a) 
services that consist of structured modifications to an operating 
system, and (b) shepherd services that define a process that will 
run on the resulting system. Shepherd services cannot be used 
directly, but need to be added to an instance of the 
shepherd-root-service-type service. The easiest way to do this is 
to use simple-service (documented in "(guix) Service Reference" in 
the manual).

Putting it together, this should return a service object which 
runs your redshift shepherd service:

  (simple-service 'redshift-service 'shepherd-root-service-type 
  (list redshift-service))

I hope that helps!

Carlo

Re: Defining custom services in /etc/config.scm

[Sergiu Ivanov]

Hi Carlo,

Thanks a lot for your answer !


Thus quoth  Carlo Zancanaro  on Sun Jan 24 2021 at 23:25 (+0100):
> On Mon, Jan 25 2021, Sergiu Ivanov wrote:
>> I understand that I should somehow construct a <service> (?) from my
>> <shepherd-service>, but I don't see a way to do it.
>
> Unfortunately Guix overloads the word "service", where we have (a)
> services that consist of structured modifications to an operating 
> system, and (b) shepherd services that define a process that will run
> on the resulting system.

A-ha, OK, I vaguely felt this distinction, but I wasn't sure.

> Shepherd services cannot be used directly, but need to be added to an
> instance of the shepherd-root-service-type service. The easiest way to
> do this is to use simple-service (documented in "(guix) Service
> Reference" in the manual).
>
> Putting it together, this should return a service object which runs
> your redshift shepherd service:
>
>  (simple-service 'redshift-service 'shepherd-root-service-type   (list
> redshift-service))
>
> I hope that helps!

This helped indeed: my redshift-service got integrated into the system
service tree.  You solved my frustration: I thought I understood almost
everything I needed from the documentation, but I couldn't put the
pieces together.  Invoking simple-service in this way made the pieces
click; I'm happy.

Still, I'll go with Shepherd user services:

  https://guix.gnu.org/blog/2020/gnu-shepherd-user-services/

Running redshift as a system service, even as my user, prevents it from
easily detecting my X session.  Also, I realized that I could even run
mcron as a user service, which actually makes several things
somewhat easier.

I initially hoped to cram as much as I could into /etc/config.scm (in
particular because guix-home-manager looks a lot less evolved than Nix's
home-manager (and that's an opportunity to contribute, but I need to get
a better grasp on Guix first)), but after all having a couple user files
written in Guile is not a big issue, because the uniformity of the
configuration language is more important for me.

-
Sergiu