Defining Subscriptions, Entitlements, and Products

The basis of everything is a subscription. A subscription contains both the products that are available, the support levels, and the quantities, or number of servers, that the product can be installed on.

Subscriptions are managed though the Certificate-Based CentOS Network service, which ties into the Subscription and Content Delivery Network (CDN).

The subscription service maintains a complete list of subscriptions for an organization, identified by a unique ID (called a pool ID). A system is registered, or added, to the subscription service to allow it to manage the subscriptions for that system. Like the subscription, the system is also added to the subscription service inventory and is assigned a unique ID within the service. The subscriptions and system entries, together, comprise the inventory.

A system allocates one of the quantities of a product in a subscription to itself. When a subscription is consumed, it is an entitlement. (An entitlement is roughly analogous to a user license, in that it grants all of the rights to that product to that system. Unlike a user license, an entitlement does not grant the right to use the software; with the subscription model, an entitlement grants the ability to download the packages and receive updates.) Because the available quantity in a subscription lowers once a system subscribes to it, the system consumes the subscription.

Figure 14.2. Managing Subscriptions, Illustrated

The repository where the product software is located is organized according to the product. Each product group within the repository may contain the primary software packages and then any required dependencies or associated packages. Altogether, the product and its associated packages are called a content set. (A content set for a product even includes other versions of the product.) When a subscription grants access to a product, it includes access to all of the associated packages in that content set.

A single subscription can have multiple products, and each system can have multiple different subscriptions, depending on how many entitlement certificates are loaded on the machine.

Any number of products, for any number of different architectures, can be contained in a single subscription. The subscription options that are visible to a consumer are filtered, by default, according to whether the architecture for the product matches the architecture of the system. This is compatibility. Depending on compatible subscriptions makes sure that subscriptions are allocated efficiently, only to systems which can actually use the products.

The subscription tools can display even incompatible entitlements. Alternatively, the architecture definition for the system can be overridden by defining custom system facts for the subscription tools to use.

It's important to distinguish between subscribing to a product and installing a product. A subscription is essentially a statement of whatever products an organization has purchased. The act of subscribing to a subscription means that a system is allowed to install the product with a valid certificate, but subscribing doesn't actually perform any installation or updates. In the reverse, a product can also be installed apart from any entitlements for the system; the system is just does not have a valid product certificate. Certificate-Based CentOS Network and the Content Delivery Network harmonize with content delivery and installation by using yum plug-ins that come with the Subscription Manager tools.