Chapter 1. Introduction

By default, Red Hat Enterprise Linux instances are registered to and obtain their content from the Customer Portal.

Red Hat Enterprise Linux instances under management with Red Hat Subscription Management are instead registered to a Subscription Management server, and obtain their Product subscriptions from it.

Modern IT infrastructure is a mix of physical and virtual hardware, with virtualization providing a level of flexibility and scalability not easily achieved with physical hardware. Red Hat’s subscription model applies to both physical and virtual servers.

A Red Hat subscription provides:

  • Access to support services
  • Content delivery and hosted repositories
  • Access to knowledgebases, forums, videos, and other resources

The Red Hat subscription model requires that for physical servers, subscriptions must cover the physical attributes of the machine, such as the number of sockets or cores. Subscriptions are always applied in sets of two to cover pairs of sockets or cores, and those subscription pairs must be attached to cover all sockets and cores. Subscriptions for virtual servers can also be purchased and applied according to their virtual CPU attributes, but there is another subscription type that might be more suitable - a Virtual Data Center (VDC) subscription, which is a host-based subscription. A host-based subscription is applied to a hypervisor and entitles the hypervisor to provide subscriptions to its virtual machines. With a host-based subscription, each guest requires one subscription, regardless of its virtual CPU configuration.

1.1. Supported Virtualization Platforms

Supported virtualization platforms to which a Virtual Data Center (VDC) subscription can be applied are:

  • Red Hat Virtualization (RHV)
  • Red Hat OpenStack Platform (RHOSP)
  • Red Hat Enterprise Linux hypervisors
  • VMware vSphere
  • Microsoft Hyper-V

    Note

    The virt-who daemon does not currently support Microsoft System Center 2012 R2 Virtual Machine Manager (SCVMM). There must be a virt-who configuration file for each Microsoft Hyper-V host to which virt-who is to connect.

A VDC subscription applies only to a hypervisor’s guest virtual machines, not the hypervisor itself. For all virtualization platforms which require a Red Hat Enterprise Linux hypervisor, the hypervisor requires its own subscription.

Virtual Instances

1.2. Choosing a Subscription

Red Hat recommends a subscription that allows virtual machines to inherit subscriptions, since this allows for flexibility when provisioning virtual machines. However the choice is yours, and should be made according to your requirements. If you are unsure which subscription best meets your needs, contact your Red Hat account manager for advice. For more details of the Red Hat subscription model, see Subscription Concepts and Workflows.

The following are example Red Hat subscriptions which provide inheritable subscriptions:

  • Red Hat Enterprise Linux for Virtual Datacenters
  • Red Hat Enterprise Linux with Smart Virtualization and Management

This guide uses a Red Hat Enterprise Linux for Virtual Datacenters (VDC) subscription in all examples. The workflow for all inheritable subscriptions is identical.

Confirming if virt-who is Required

To confirm if the virt-who daemon is required, either use the Red Hat Certificate Tool, or contact Red Hat Support. The command line Red Hat Certificate Tool (rct) reads a Subscription Manifest file and displays details of the manifest in plain text. The Red Hat Certificate Tool is available in subscription-manager-1.17.10 (or later) package, in either Red Hat Enterprise Linux 7.3 or Fedora 24.

Examining a Subscription Manifest with the Red Hat Certificate Tool

  1. Download the Subscription Manifest from the Customer Portal.
  2. Run the command line Red Hat Certificate Tool.

    # rct cat-manifest --no-content manifest_file.zip

    The following extract is from an OpenShift Container Platform, Premium (1-2 Sockets) subscription.

    Subscription:
        Name: OpenShift Container Platform, Premium (1-2 Sockets)
        Quantity: 50
        Created: 2017-09-16T01:47:59.000+0000
        Start Date: 2017-07-04T04:00:00.000+0000
        End Date: 2018-07-04T03:59:59.000+0000
        .
        .
        .
        Virt Limit: unlimited
        Requires Virt-who: True

The virt-who daemon is required if the rct output includes Virt Limit: unlimited, Requires Virt-who: True, or both. In this example, both are included, confirming that the virt-who daemon is required.

1.3. Applying Virtual Guest Subscriptions

A Virtual Data Center (VDC) subscription is one type of host-based subscription offered by Red Hat. Host-based subscriptions are applied to a host and inherited by its guests. Host-based subscriptions consist of two parts, a pool attached to the virtualization manager or hypervisor, and a pool from which virtual guests inherit their subscription. It is important to note that the virtualization manager or hypervisor’s subscription does not provide entitlement to product content.

To successfully provision virtual machines, and ensure they inherit host subscriptions, you must do the following:

  1. Ensure that a manifest including a VDC subscription has been uploaded to Satellite Server. See Importing a Subscription Manifest into the Satellite Server in the Content Management Guide.
  2. Install and configure the virt-who service. See Chapter 5, Configuration and Services.
  3. Attach a VDC subscription to the hypervisor. To attach a VDC subscription to a hypervisor using the web UI, click Hosts → Content Hosts, select a host, and click Subscriptions → Subscriptions. Click Add, select the desired subscription, and click Add Selected.
  4. Restart the virt-who service so that the hypervisor and virtual machine mapping information is sent back to Satellite.
  5. Register virtual machines with an activation key that has auto-attach enabled and no subscriptions attached. This way, the virtual machines will inherit the VDC subscription from the hypervisor.

1.4. Registering temporary virtual guests

When a virtual machine is first registered, Satellite does not know with which virtualization manager or hypervisor the virtual machine is associated and so cannot assign a subscription. In this case a temporary subscription is granted, valid for a maximum period of 24 hours.

When the virt-who daemon next runs and identifies the virtual machine’s host, a permanent subscription is applied, provided the host has available subscriptions of the right type. If a permanent subscription is granted, the virtual machine’s subscription status is changed to Subscribed.

A virtual machine that has been granted a temporary subscription might, after the 24-hour period, automatically select a subscription intended for a physical host and so restrict the number of subscriptions available. When the 24-hour period expires, the host’s status is changed to Not subscribed if it has been unable to request a suitable subscription.

When a virtual machine is granted a temporary subscription, you have several options available:

  • Install virt-who and wait
  • If virt-who has not already been installed and configured, do so, then wait for virt-who to identify the virtualization manager or hypervisor hosting the virtual machine, in which case the subscription will be automatically selected from those available.
  • Manually assign a subscription.
  • If you do not want to wait for up to 24 hours to pass, or you want to assign a specific subscription, install and configure virt-who, then manually assign the desired subscription.
  • Do nothing.

This situation should be avoided as it results in more subscriptions being consumed than would otherwise be consumed. A virtual machine assigned a temporary subscription might be assigned subscriptions intended for physical hosts. For example, a virtual machine with 2 CPUs might be granted two subscriptions instead of a single VDC subscription.

1.5. Virtual Machine Subscription Process

The process of registering a virtual machine is as follows:

  1. A virtual machine is provisioned.
  2. The virtual machine requests a subscription from Subscription Manager.
  3. As the subscription manager doesn’t yet know to which host the virtual machine belongs, a temporary subscription is granted, valid for a maximum 24 hours.
  4. The virt-who daemon connects to the virtualization manager or hypervisor and requests details of the guest virtual machines. By default, this request is made every hour, but the interval is configurable. Red Hat recommends this value remain at the default unless requested by Red Hat Support.
  5. The virtualization manager or hypervisor returns to virt-who the list of guest virtual machines, including each UUID.
  6. The virt-who daemon reports to Subscription Manager the list of guest virtual machines.
  7. Subscription Manager then reconciles the subscriptions required by the virtual machines with those available. If the required subscriptions are available, they are assigned to the virtual machine and its subscription is complete.

1.6. Subscription Status

A registered host, virtual or physical, has a subscription status based on its installed Products and attached subscriptions.

Subscription Status Meanings

  • Red

    • The host has Products installed that valid subscriptions do not cover. Hosts in a Red status cannot access content for Products not covered by subscriptions. Manual intervention is required to resolve a subscription with this status.
  • Yellow

    • Either the host has insufficient subscriptions or an incorrect quantity of subscriptions is attached (for example, a 2-socket subscription is attached to a 4-socket host), or Subscription Management does not know which virtualization manager or hypervisor hosts the virtual machine and has assigned a temporary subscription. Insufficient subscriptions must be resolved manually. Temporary subscriptions will be automatically resolved by Subscription Management, providing there are enough subscriptions available.
  • Green

    • The host is correctly subscribed.
Note

Hypervisors always appear in the Subscription Management web UI as correctly subscribed, regardless of their actual status.

1.6.1. Temporary Subscriptions

When a virtual machine is first registered, Subscription Management does not know with which virtualization manager or hypervisor the virtual machine is associated and so cannot assign a subscription. In this case a temporary subscription is granted, valid for a maximum period of 24 hours. When the virt-who daemon next runs and identifies the virtual machine’s host, a permanent subscription is applied, provided the host has available subscriptions of the right type. If a permanent subscription is granted, the virtual machine’s subscription status is changed to Subscribed. A virtual machine that has been granted a temporary subscription might, after the 24-hour period, automatically select a subscription intended for a physical host and so restrict the number of subscriptions available. When the 24-hour period expires, the host’s status is changed to Not subscribed if it has been unable to request a suitable subscription.

When a virtual machine is granted a temporary subscription, you have several options available:

  • Install virt-who and wait

    If virt-who has not already been installed and configured, do so, then wait for virt-who to identify the virtualization manager or hypervisor hosting the virtual machine, in which case the subscription will be automatically selected from those available.

  • Manually assign a subscription

    If you do not want to wait for up to 24 hours to pass, or you want to assign a specific subscription, install and configure virt-who, then manually assign the desired subscription.

  • Do nothing

    This situation should be avoided as it results in more subscriptions being consumed than would otherwise be consumed. A virtual machine assigned a temporary subscription might be assigned subscriptions intended for physical hosts. For example, a virtual machine with 2 CPUs might be granted two subscriptions instead of a single VDC subscription.

1.6.2. Virtual Machine Migration

When a virtual machine is migrated either automatically or manually to another hypervisor that is registered to Red Hat Satellite, one of the following virtual machine subscription behaviors can occur:

  • If the virtual machine has been reported via virt-who, and the hypervisor has a valid VDC subscription, the virtual machine will consume the virtual guest pool that already exists for the hypervisor. Ideally, all hypervisors that could be hosting the virtual machine should have a valid VDC subscription.
  • If the virtual machine has been reported via virt-who, and there are sufficient subscriptions in Red Hat Satellite, but the hypervisor does not yet have a valid VDC subscription attached, a VDC subscription will get automatically attached to the hypervisor and be inherited by the virtual machine.
  • If there are sufficient subscriptions in Red Hat Satellite, but the virtual machine has not been reported via virt-who, the virtual machine will consume a physical subscription.
  • If the hypervisor does not have a valid VDC subscription attached, and there are insufficient subscriptions in Red Hat Satellite, the virtual machine will not have a valid subscription and lose access to content.