diff -r b688d4a68a3e tools/python/xen/xend/server/blkif.py
--- a/tools/python/xen/xend/server/blkif.py	Tue Aug 22 14:59:16 2006 +0100
+++ b/tools/python/xen/xend/server/blkif.py	Thu Aug 24 10:12:15 2006 +0800
@@ -107,7 +107,7 @@ class BlkifController(DevController):
             if dev_type:
                 dev += ":" + dev_type
             result.append(['dev', dev])
-        if typ and params:
+        if typ and params or ":cdrom" in dev:      # allow empty cdrom
             result.append(['uname', typ + ":" + params])
         if mode:
             result.append(['mode', mode])