Recently we used VMWare to clone an existing, registered Oracle Linux machine, and while it worked fine in general, it refused to register with ULN. When I ran uln_register (this is an OL 6 machine) it said the machine was already registered. This was after I regenerated the RHN UUID by using uuidgen and putting the resulting key in /etc/sysconfig/rhn/up2date.
The resolution was to remove /etc/sysconfig/rhn/systemid and re-run uln_register. Apparently this file also keeps some record of a machine’s “uniqueness” but isn’t well documented in the ULN FAQs.
