and this is my configuration

;; This is an operating system configuration template
;; for a "desktop" setup with GNOME and Xfce where the
;; root partition is encrypted with LUKS.

(use-modules (gnu) (gnu system nss))
(use-modules (gnu packages tryton))
(use-modules (gnu packages databases))
(use-service-modules desktop)
(use-package-modules certs gnome)
(use-service-modules databases)
;(use-service-modules trytond)

(operating-system
  (host-name "antelope")
  (timezone "Europe/Paris")
  (locale "it_IT.utf8")

  ;;This is to be able to login into a guest system
  (kernel-arguments '("console=ttyS0"))

  ;; Assuming /dev/sdX is the target hard disk, and "my-root"
  ;; is the label of the target root file system.
  (bootloader (grub-configuration (target "/dev/sda")))

  (file-systems (cons (file-system
                        (device "my-root")
                        (title 'label)
                        (mount-point "/")
                        (type "ext4")

                      )
                      %base-file-systems))

  (users (cons (user-account
                (name "catonano")
                (comment "Alice's brother")
                (group "users")
                (supplementary-groups '("wheel" "netdev"
                                        "audio" "video"))
                (home-directory "/home/catonano"))
               %base-user-accounts))

  ;; This is where we specify system-wide packages.
  (packages (cons* nss-certs         ;for HTTPS access
                   gvfs              ;for user mounts
           ;;python-trytond
           ;;tryton
           ;;postgresql
                   %base-packages))

  ;; Add GNOME and/or Xfce---we can choose at the log-in
  ;; screen with F1.  Use the "desktop" services, which
  ;; include the X11 log-in service, networking with Wicd,
  ;; and more.
  (services (cons* ;(postgresql-service #:locale "it_IT.UTF-8")
                   ;(service trytond-service-type)
                   (gnome-desktop-service)
                   ;(xfce-desktop-service)
           (service agetty-service-type
                (agetty-configuration (tty "ttyS0")))
                   %desktop-services))

  ;; Allow resolution of '.local' host names with mDNS.
  (name-service-switch %mdns-host-lookup-nss))