Hello, Ricardo Wurmus! ok, thank you. But now I've not achieved what I need. avahi-damon, ntpd, networking rest in my system. 

  (services (cons*  ;;(tor-service)
                    (service postgresql-service-type)
                    (xfce-desktop-service)
                    (modify-services      
                      (remove (lambda (service)
                        (eq? (service-kind service) 
                               avahi-service-type ntp-service-type networking))
                        %desktop-services
                      );end of remove
                      (elogind-service-type
                        c => (elogind-configuration (handle-lid-switch 'ignore)))
                    );;end of modify desktop-services
  ));;end of services

Also they are mentioned in use-modules:

(use-modules (gnu) (gnu system nss)
             (gnu services desktop)
             (srfi srfi-1) ;;for remove function
             (gnu services networking) ;;for remove ntp
             (gnu services avahi) ;;for remove avahi
             (gnu services xorg)
             (gnu services databases);;for postgres
)
(use-service-modules desktop)
(use-package-modules certs gnome)

But if I delete this use-modules lines, remove line will give the errors: unbound variable avahi-service-type, ntp-service-type, networking. 
So, how to correct I do not know.


Nov 30, 2018, 5:55 AM by rekado@elephly.net <mailto:rekado@elephly.net>:

>
> znavko@tutanota.com <mailto:znavko@tutanota.com>>  writes:
>
>> Guile Manual says 'remove' returns elements. But I need to remove elements.
>>
>
> “remove” does what you want.  The “services” field expects a list of
> services.  When using “remove” on a list of services it returns a new
> list of (possibly fewer) services.  That’s exactly what you want.
>
> “remove!”, on the other hand, mutates an existing value; you would need
> to have it operate on an existing variable to mutate it.  “remove” is
> much more elegant.
>
> --
> Ricardo
>