Using RHEL Virtual Data Center Subscription [Master Article]

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  • Virtual Data Center(VDC) subscription
  • Red Hat Enterprise Linux



This scenario describes the situation where you have a host system, such as VMware, HyperV host, RHEV-H, or Nutanix AHV with which you want to use an unlimited number of RHEL virtual machines. We refer to this configuration as a "Virtual Datacenter." The following figure illustrates this type of configuration:

Configuring Datacenter Subscriptions

  • What is virt-who?

    • Virt-who is an agent for reporting virtual guest IDs to Red Hat Customer Portal.
    • Virt-who authenticates with the server using the username and password provided in the config file.
    • It has the ability to scan for third-party hypervisors and register them on the Red Hat Customer Portal.
    • Virt-who also uploads the list of guest UUIDs/Hostname associated with the hypervisors.
  • Why virt-who?

    • Guests running on a hypervisor do not know what host they are running on (for the security of the hypervisor infrastructure). So, the subscription service cannot completely reconcile the guest subscription until the host-guest mapping is available.

    • The virt-who agent interrogates the hypervisor infrastructure and provides the host-guest mapping to the subscription service. Here’s how: the virt-who agent uses read-only commands to gather the host-guest associations for the subscription services. This way, the guest subscriptions offered by a subscription can be unlocked and made available for the guests to use.

    • More information on "why and when do I need Virt-Who?" can be found here and Virt-Who Process, Queries and Data can be found here

  • Vcenter user access permission details

  • What is VDC?

    • A Virtual Datacenter (VDC) is a collection of cloud-based resources that replace the need for you to operate your own data center. In practical terms, you no longer need to buy and house your own servers, and instead of them residing on your premises, you have access to virtual servers to which you give access to all of the business applications you use.

    • Rather than physical servers, you now have virtual servers, and this provides the ability to be flexible and to scale up as needed. In essence, you can have as many virtual servers as you will ever need and without the need to invest in purchasing, provisioning, housing and maintaining a physical machine.

  • Prerequisites for VDC configuration?

    • A Virtual Machine with RHEL 6 or RHEL 7 OS installed. A Virtual Machine with RHEL 7.9, 8.2, or 8.4 OS installed is required for Nutanix AHV.
    • The Virtual Machine (VM) must have internet connectivity. Because virt-who requires internet connectivity to communicate with the customer portal to report the Hypervisors profile on the Red Hat Customer Portal.
    • The VM should be able to reach the Customer portal. If there is any firewall or proxy in the network whitelist the URLs provided in How to access Red Hat Subscription Manager (RHSM) through a firewall or proxy
    • Proper communication between the Hypervisor/Host and the guest/VM needs to be possible.
    • The hypervisor is not required to have a connection to the internet/the Customer portal.
  • What are supported hypervisors for VDC?

    • Certified hypervisors that have been tested and proven to run Red Hat Enterprise Linux as a guest are available from Red Hat and third parties.

    • Red Hat virtualization products/hypervisor hosts:

      • Red Hat Enterprise Linux OpenStack Platform
      • Red Hat Enterprise Virtualization
      • Red Hat Enterprise Linux with KVM
    • Third-party hypervisors or hosts:

      • Microsoft Hyper-V
      • VMware ESXi and ESX
      • Nutanix AHV
    • More information on "which hypervisors are certified to run Red Hat Enterprise Linux?" can be found here

  • How to configure VDC on supported hypervisors?

  • How VDC registration works in offline environment ?

  • What problems will happen when virt-who is down?

      - The clients which existed before virt-who was down, will NOT be affected.
    (The clients do not need to subscribe systems again after virt-who is up. )
    - If a new VM is created when virt-who is down, the new guests will not get reported because the information is not sent to customer portal by virt-who. However, the impact will be limited, because the new VMs can still be registered and updated. 
    - The problem is that the expiration date of the subscription of new clients will be of the next day. system will be temporarily subscribed as mentioned below:-
    # subscription-manager list --consumed
    Consumed Subscriptions
    Subscription Name:   Red Hat Enterprise Linux for Virtual Datacenters, Standard
    Provides:                       Red Hat Developer Toolset (for RHEL Server)
    Status Details:             Guest has not been reported on any host and is using a temporary unmapped guest  <------ `This is a warning message`
    Subscription Type:     Stackable (Temporary)  <------ `Warning again! this is temporary`
    Starts:                            09/30/15
    Ends:                              06/22/16  <------ `only one day`
    System Type:               Virtual
    - So, the new VM will need to be re-registered after virt-who is up.
    • Should we use virt-who in the redundant configuration?
      • A redundant configuration can be achieved by selecting one of the two ways below:
        1. Run virt-who in multiple environments.
        (We can run virt-who in multiple environments at the same time for redundant configuration)
        2. Run virt-who in a cluster system.
  • Troubleshooting common VDC issues?

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After reading this article I have some questions and would like to ask if someone could answer them:

  1. Is it possible to use this subscription for a mixed cluster with Windows and Linux guests?
  2. We are managing multiple vSphere Clusters with one vCenter Server. Is it possible to use the virtual datacenter subscription for only one vSphere Cluster? Or do I have to buy subscriptions for all ESXi hosts in all vSphere Clusters managed by one vCenter Server?

Kind regards,
Joerg K.

Hello Jörg,

You need one VirtualDatacenter licence per each ESXi host for 2 CPU Sockets. You don't need to buy for all of them if not needed, just buy for each hosts you want to deploy RHEL VM's. Regards, Fabio Dias

Hello Fábio,
Thanks for clarifying that!

And to give an answer to my first question myself: "Yes, you could use this subscriptions for mixed clusters."


In virt-who config by a whitelist and on the ESX cluster you need to configure on which ESX hosts by affinity rules you are deploying the RHEL VMs, this way you do not need VDC subs for ESX hosts in a VMware cluster that do not run RHEL vms.


Jan Gerrit Kootstra

Hi Jörg,

  1. Is it possible to use this subscription for a mixed cluster with Windows and Linux guests? [A] Yes and the virt-who agent will only look for the RHEL guest mapping while capturing the information from the host/hypervisor.

  2. We are managing multiple vSphere Clusters with one vCenter Server. Is it possible to use the virtual datacenter subscription for only one vSphere Cluster? Or do I have to buy subscriptions for all ESXi hosts in all vSphere Clusters managed by one vCenter Server? [A] This is a host-based subscription, for example, if your vCenter cluster has 10 ESXi Hypervisors and all have RHEL then subscribe to all the VMs running on the hypervisor you would need 10 subscriptions.

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