Chapter 6. Managing Hypervisors and Virtual Guest Subscriptions

Red Hat Satellite can track the hypervisors (hosts) that are attached directly to it and the subscriptions of those hosts. However, the hypervisors’ guests are not indexed through this mechanism. For the security of the hypervisor infrastructure, this host to guest mapping is not provided during Satellite registration.
The virt-who utility collects information about the connection between the hypervisor and its virtual guests and provides Subscription Manager with a mapping file containing the hypervisor-guest pairs. This utility is provided both in the main Red Hat Enterprise Linux repository (rhel-6-server-rpms or rhel-7-server-rpms) as well as in the Red Hat Satellite Tools repository (rhel-6-server-satellite-tools-6.1-rpms or rhel-7-server-satellite-tools-6.1-rpms). The Satellite Tools repository is the recommended source of virt-who for Satellite installations. To enable this repository on Red Hat Enterprise Linux 7, execute: 
# subscription-manager repos --enable=rhel-7-server-satellite-tools-6.1-rpms
Then install virt-who as follows: 
# yum install virt-who

6.1. Introduction to virt-who

Red Hat uses virt-who to keep track of the hypervisors’ subscriptions and the guests who can inherit those subscriptions. The virt-who system:
  1. Scans the hypervisor (host) management platform and its guests
  2. Creates the host/guest mapping
  3. Communicates this host/guest mapping to Satellite
This host/guest mapping associates every guest with a specific host. Then, a subscription service can attach a single subscription to a virtual host and apply an included and inheritable subscription to a guest, rather than consuming two separate subscriptions for each instance.
After you start virt-who the first time, a virt-who daemon automatically runs in the background and makes updates based on a schedule you select (the default is hourly).

6.1.1. The Universally Unique Identifier (UUID)

The virt-who system makes this host/guest association by extracting a universally unique identifier (UUID) for each guest from the hypervisor and then associating each UUID with its hypervisor in the Satellite inventory.

6.1.2. Important Conditions for virt-who to Correctly Attach Subscriptions

These factors must be true for the subscription service to recognize the host/guest association and correctly attach subscriptions:
  • The virt-who system must be run periodically to detect new guest instances.
  • The hypervisor and the guest systems must be registered to the same subscription service (that is, the same Satellite organization).
  • The hypervisor must have a subscription attached to it that includes virtual subscriptions or inheritable subscriptions.

6.1.3. Subscription Status and virt-who

A registered host is assigned a subscription status color based on its installed products and attached subscriptions. When you first register a virtual guest, the host list displays that virtual guest's host subscription status as yellow. The reason is that the Satellite does not know which hypervisor the guest resides on. You must run virt-who so that the Satellite knows which hypervisor the guest resides on. With the default auto-attach configuration enabled, and assuming virt-who runs successfully, the guest subscription displays as green in 24 hours.