feat: reload on private key change

monit.conf

@@ -1,3 +1,8 @@
 check process opendkim with pidfile /tmp/opendkim.pid
   start program = "/usr/local/bin/opendkimd start"
   stop program = "/usr/local/bin/opendkimd stop"
+
+check program key_rotation
+  with path "/usr/local/bin/opendkimd rotate"
+  every 1 cycle
+  if status != 0 then alert

opendkimd.sh

@@ -4,7 +4,8 @@ pid=/tmp/opendkim.pid
 
 case $1 in
   stop)
-    test -f ${pid} && cat ${pid} | xargs kill
+    test -f $pid && cat $pid | xargs kill
+    rm -f $pid
     ;;
   start)
     install -dm 2750 -o opendkim -g opendkim /run/opendkim
@@ -12,4 +13,8 @@ case $1 in
 
     /usr/sbin/opendkim
     ;;
+  rotate)
+    test -f $pid || exit 0
+    test $pid -ot /etc/opendkim/dkim.private && cat $pid | xargs -r kill -USR1
+    ;;
 esac