Index: amazon-ec2-utils/60-cdrom_id.rules
===================================================================
--- amazon-ec2-utils.orig/60-cdrom_id.rules
+++ amazon-ec2-utils/60-cdrom_id.rules
@@ -6,3 +6,7 @@
 
 # This is an empty placeholder file used to signal udev to
 # skip probing for cd/dvd drive capabilities.
+# It is installed by the amazon-ec2-utils package and replaces the
+# content provided by the same file in the udev package.  The original
+# file is preserved as /lib/udev/rules.d/60-cdrom_id.rules.disabled.
+# See dpkg-divert(1).
