Index: etc/mtree/BSD.root.dist
===================================================================
--- etc/mtree/BSD.root.dist
+++ etc/mtree/BSD.root.dist
@@ -94,6 +94,8 @@
         ..
         ssl
         ..
+        sysctl.conf.d
+        ..
         syslog.d
         ..
         zfs
Index: libexec/rc/rc.d/sysctl
===================================================================
--- libexec/rc/rc.d/sysctl
+++ libexec/rc/rc.d/sysctl
@@ -27,7 +27,7 @@
 	;;
 	esac
 
-	for _f in /etc/sysctl.conf /etc/sysctl.conf.local; do
+	for _f in /etc/sysctl.conf /etc/sysctl.conf.local /etc/sysctl.conf.d/*.conf; do
 		if [ -r ${_f} ]; then
 			${command} ${command_args} ${_f} > /dev/null
 		fi
Index: share/man/man5/sysctl.conf.5
===================================================================
--- share/man/man5/sysctl.conf.5
+++ share/man/man5/sysctl.conf.5
@@ -59,6 +59,10 @@
 .It Pa /etc/sysctl.conf.local
 Machine-specific settings for sites with a common
 .Pa /etc/sysctl.conf .
+.It Pa /etc/sysctl.conf.d
+Directory for modularized
+.Xr sysctl 8
+files.
 .El
 .Sh EXAMPLES
 To turn off logging of programs that exit due to fatal signals you may use