Switch to dhcpd.conf.d

This commit adds dhcpd.conf.d as a directory for containing
configuration file fragments.  This permits the dhcpd instance to be
configured almost entirely by the sg-dhcp role, but for additional
assets such as a file containing MAC addresses to be 'dropped in'.  A
script is also provided in /usr/local/sbin/dhcpd-reconf which will
reconfigure the dhcpd server and restart it.

files/dhcpd-reconf

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+
+# This assembles all of the snippets into a complete configuration file
+cat /etc/dhcpd.conf.d/* > /etc/dhcpd.conf
+
+# Restart dhcpd iff the new config file checks out
+if dhcpd -n ; then
+    /etc/rc.d/dhcpd restart
+else
+    printf "Refusing to restart dhcpd: dhcpd.conf contains errors!\n"
+fi

handlers/main.yml

@@ -1,3 +1,3 @@
 ---
 - name: dhcpd
-  command: /etc/rc.d/dhcpd restart
+  command: /usr/local/sbin/dhcpd-reconf

tasks/main.yml

@@ -1,8 +1,16 @@
 ---
-- name: Configure dhcpd
+- name: Create dhcpd.conf.d
+  file:
+    path: /etc/dhcpd.conf.d
+    state: directory
+    owner: root
+    group: wheel
+    mode: 0755
+
+- name: Configure dhcpd core
   template:
     src: dhcpd.conf.j2
-    dest: /etc/dhcpd.conf
+    dest: /etc/dhcpd.conf.d/10-core
     owner: root
     group: wheel
     mode: 0644
@@ -18,3 +26,11 @@
     mode: 0644
   notify:
     - rc.conf.local
+
+- name: Install dhcpd-reconf
+  copy:
+    src: dhcpd-reconf
+    dest: /usr/local/sbin/dhcpd-reconf
+    owner: root
+    group: wheel
+    mode: 0755