7.2. About Host/Guest Associations

Subscription relationships have a lot of potential flexibility. Some subscriptions can be applied to a physical machine or to a certain number of virtual machines, while others can be applied to a physical host and then inherited by guests. This is covered in detail in Section 5.1, “About Subscriptions on Systems”.
For subscriptions to be managed effectively — particularly with inheritable subscriptions or interactions between subscriptions — there has to be an internal awareness in the subscription service of the relationships between hosts and guests. This is a host/guest mapping, which is literally a list of all of the guest identifiers for a given hypervisor.
Hypervisors are registered as a special type of consumer in Subscription Asset Manager or Customer Portal Subscription Management. Hypervisors themselves are managed as regular physical systems, but the hypervisor type indicates that that particular system will have guests mapped to it, and that subscriptions may be inheritable or applied differently to those guests.
With a host/guest mapping to associate every guest with a specific host, a subscription service can properly attach a single subscription to a virtual host and then apply an included and inheritable subscription to its guest (for example), rather than consuming two separate subscriptions for each instance.
This association is done by extracting a universally unique identifier for each guest and associating it with its hypervisor. These UUIDs are part of the system facts for each virtual system.
The hypervisor is registered first with Subscription Asset Manager, and then a related process on the system scans for any guests and submits the discovered UUIDs to the subscription service. This is done by the virt-who process on the hypervisor.
There are three factors that must be true for Subscription Asset Manager to recognize the host/guest association and properly attach subscriptions:
  • The appropriate virtual detection process must be run periodically to detect new guest instances.
  • The hypervisor and the guest systems must be registered to the same Subscription Asset Manager instance.
  • The hypervisor must have a subscription attached to it that includes virtual subscriptions or inheritable subscriptions.