# Generic service definition template
define service{
        name                            generic-service
        active_checks_enabled           1
        passive_checks_enabled          1
        parallelize_check               1
        obsess_over_service             1
        check_freshness                 0
        notifications_enabled           1
        event_handler_enabled           1
        flap_detection_enabled          1
        process_perf_data               1
        retain_status_information       1
        retain_nonstatus_information    1
        register                        0
        }



define service{
        host_name                       somehost
        service_description             HTTP
        max_check_attempts              4
        event_handler                   restart-httpd
        }

define command{
        command_name    restart-httpd
        command_line    /usr/local/nagios/libexec/eventhandlers/restart-httpd  $SERVICESTATE$ $SERVICESTATETYPE$ $SERVICEATTEMPT$
        }


#################################################
what I have in hosts.cfg

define hostgroup{
        hostgroup_name  nod1
        alias           Nod 1
        members         server1,server2,server3
        }