3.9. General Management: Hypervisors and Guests

Red Hat Enterprise Linux has an optional service which can automatically detect guests on a virtual host system, create a map of hosts to guests, and register guests as virtual systems. This allows subscriptions which are specific to virtual systems to be available to the guest and for subscriptions which are inherited from the host to be applied to the guest automatically.
The virt-who process can detect and associate guests on several different types of hypervisors:
  • Red Hat Enterprise Virtualization Manager (KVM)
  • Xen
  • HyperV
  • VMware ESX

3.9.1. The Environment: Data Centers, Cloud Environments, Any Environment Using Virtual Machines

Note

If your environment has a large number of virtual systems or depends on creating and destroying virtual systems (such as test environments or private clouds), then consider using Subscription Asset Manager to manage subscription services. Subscription Asset Manager allows administrators to define organizations to group subscriptions for systems and then groups within those organizations to control content flows within those organizations.
Subscription Asset Manager is available with any Red Hat Enterprise Linux subscription.
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, 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.

3.9.2. Workflow

  1. If registering with a Subscription Asset Manager instance, install the Subscription Asset Manager RPM to configure Red Hat Subscription Manager.
  2. Register the system as hypervisor, using the --type=hypervisor option with the subscription-manager command.
  3. Install virt-who on a Red Hat Enterprise Linux system within the infrastructure. This Red Hat Enterprise Linux system manages the mapping and communicates with Red Hat Enterprise Linux guests, the hypervisor, and the backend subscription service, even if the hypervisor itself is not a Red Hat Enterprise Linux system.
    If the Red Hat Enterprise Linux system is ever unavailable, the host/guest mapping is not available, and virtual systems are treated as physical systems.
  4. For VMware or for environments using Subscription Asset Manager. Edit the virt-who configuration file (/etc/sysconfig/virt-who) to recognize the appropriate virtualization and subscription services.
  5. Start the virt-who process to create the host-guest mapping.