diff --git a/etc/diskcheckd.conf b/etc/diskcheckd.conf
index a3f8d2afc511..e6ae6446f627 100644
--- a/etc/diskcheckd.conf
+++ b/etc/diskcheckd.conf
@@ -3,6 +3,15 @@
 # Configuration file for diskcheckd, refer to the diskcheckd.conf(5) manual
 # page for further information.
 #
+# First, a line starting with an exclamation mark should contain only one
+# extra field which specifies disk types which should not be included in
+# wildcard expansions.  By default CD-ROM drives and memory disks are
+# excluded.
+#
+!acd
+!cd
+!md
+#
 # The device name may be specified as "*", in which case all devices are
 # checked.
 #