diff -up ./sample-config/nagios.cfg.in.conf_d ./sample-config/nagios.cfg.in
--- ./sample-config/nagios.cfg.in.conf_d 2017-08-24 17:43:48.000000000 -0400
+++ ./sample-config/nagios.cfg.in 2017-09-15 18:29:48.659666387 -0400
@@ -53,6 +53,8 @@ cfg_file=@sysconfdir@/objects/localhost.
#cfg_dir=@sysconfdir@/switches
#cfg_dir=@sysconfdir@/routers
+cfg_dir=@sysconfdir@/conf.d
+