[root@an-node01 ~]# virsh sysinfo | grep uuid
    <entry name='uuid'>03000200-0400-0500-0006-000700080009</entry>

[root@an-node01 ~]# diff -u /etc/libvirt/libvirtd.conf.orig /etc/libvirt/libvirtd.conf
--- /etc/libvirt/libvirtd.conf.orig	2011-12-27 22:29:01.243394880 -0500
+++ /etc/libvirt/libvirtd.conf	2011-12-27 22:59:02.738640396 -0500
@@ -365,4 +365,4 @@
 # NB This default all-zeros UUID will not work. Replace
 # it with the output of the 'uuidgen' command and then
 # uncomment this entry
-#host_uuid = "00000000-0000-0000-0000-000000000000"
+host_uuid = "31873B9E-1069-42CE-B950-137AE5EAA3D1"

[root@an-node01 ~]# /etc/init.d/libvirtd restart
Stopping libvirtd daemon:                                  [  OK  ]
Starting libvirtd daemon:                                  [  OK  ]

[root@an-node01 ~]# virsh sysinfo | grep uuid    <entry name='uuid'>03000200-0400-0500-0006-000700080009</entry>

[root@an-node01 ~]# rpm -q libvirt
libvirt-0.9.4-23.el6_2.1.x86_64