--- /etc/default/grub.d/dmraid2mdadm.cfg	2014-02-28 06:11:21.000000000 -0500
+++ ./dmraid2mdadm.cfg	2014-07-25 00:48:16.217938471 -0400
@@ -1 +1,16 @@
-GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT nomdmonddf nomdmonisw"
+add_if_not_found () {
+  local keywords
+  local temp
+
+  keywords="nomdmonddf nomdmonisw"
+
+  if [ -z "$GRUB_CMDLINE_LINUX_DEFAULT" ] ; then
+    GRUB_CMDLINE_LINUX_DEFAULT="$keywords"
+  else
+    temp=" $GRUB_CMDLINE_LINUX_DEFAULT "
+    [ "${temp%* $keywords *}" = "$temp" ] &&
+      GRUB_CMDLINE_LINUX_DEFAULT="$GRUB_CMDLINE_LINUX_DEFAULT $keywords"
+  fi
+}
+
+add_if_not_found