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Chapter 4. Installing

4.1. Preparing your cluster for OpenShift Virtualization

Review this section before you install OpenShift Virtualization to ensure that your cluster meets the requirements.

Important
Installation method considerations
You can use any installation method, including user-provisioned, installer-provisioned, or assisted installer, to deploy OpenShift Container Platform. However, the installation method and the cluster topology might affect OpenShift Virtualization functionality, such as snapshots or live migration.
Red Hat OpenShift Data Foundation
If you deploy OpenShift Virtualization with Red Hat OpenShift Data Foundation, you must create a dedicated storage class for Windows virtual machine disks. See Optimizing ODF PersistentVolumes for Windows VMs for details.
IPv6
You cannot run OpenShift Virtualization on a single-stack IPv6 cluster.

FIPS mode

If you install your cluster in FIPS mode, no additional setup is required for OpenShift Virtualization.

4.1.1. Supported platforms

You can use the following platforms with OpenShift Virtualization:

Bare metal instances or servers offered by other cloud providers are not supported.

4.1.1.1. OpenShift Virtualization on AWS bare metal

You can run OpenShift Virtualization on an Amazon Web Services (AWS) bare-metal OpenShift Container Platform cluster.

Note

OpenShift Virtualization is also supported on Red Hat OpenShift Service on AWS (ROSA) Classic clusters, which have the same configuration requirements as AWS bare-metal clusters.

Before you set up your cluster, review the following summary of supported features and limitations:

Installing

  • You can install the cluster by using installer-provisioned infrastructure, ensuring that you specify bare-metal instance types for the worker nodes by editing the install-config.yaml file. For example, you can use the c5n.metal type value for a machine based on x86_64 architecture.

    For more information, see the OpenShift Container Platform documentation about installing on AWS.

Accessing virtual machines (VMs)
  • There is no change to how you access VMs by using the virtctl CLI tool or the OpenShift Container Platform web console.

  • You can expose VMs by using a NodePort or LoadBalancer service.

    • The load balancer approach is preferable because OpenShift Container Platform automatically creates the load balancer in AWS and manages its lifecycle. A security group is also created for the load balancer, and you can use annotations to attach existing security groups. When you remove the service, OpenShift Container Platform removes the load balancer and its associated resources.
Networking
  • You cannot use Single Root I/O Virtualization (SR-IOV) or bridge Container Network Interface (CNI) networks, including virtual LAN (VLAN). If your application requires a flat layer 2 network or control over the IP pool, consider using OVN-Kubernetes secondary overlay networks.
Storage

  • You can use any storage solution that is certified by the storage vendor to work with the underlying platform.

    Important

    AWS bare-metal and ROSA clusters might have different supported storage solutions. Ensure that you confirm support with your storage vendor.

  • Using Amazon Elastic File System (EFS) or Amazon Elastic Block Store (EBS) with OpenShift Virtualization might cause performance and functionality limitations. Consider using CSI storage, which supports ReadWriteMany (RWX), cloning, and snapshots to enable live migration, fast VM creation, and VM snapshots capabilities.
Hosted control planes (HCPs)
  • HCPs for OpenShift Virtualization are not currently supported on AWS infrastructure.

Additional resources

4.1.2. Hardware and operating system requirements

Review the following hardware and operating system requirements for OpenShift Virtualization.

4.1.2.1. CPU requirements

  • Supported by Red Hat Enterprise Linux (RHEL) 9.

    See Red Hat Ecosystem Catalog for supported CPUs.

    Note

    If your worker nodes have different CPUs, live migration failures might occur because different CPUs have different capabilities. You can mitigate this issue by ensuring that your worker nodes have CPUs with the appropriate capacity and by configuring node affinity rules for your virtual machines.

    See Configuring a required node affinity rule for details.

  • Support for AMD and Intel 64-bit architectures (x86-64-v2).
  • Support for Intel 64 or AMD64 CPU extensions.
  • Intel VT or AMD-V hardware virtualization extensions enabled.
  • NX (no execute) flag enabled.

4.1.2.2. Operating system requirements

  • Red Hat Enterprise Linux CoreOS (RHCOS) installed on worker nodes.

    See About RHCOS for details.

    Note

    RHEL worker nodes are not supported.

4.1.2.3. Storage requirements

  • Supported by OpenShift Container Platform. See Optimizing storage.
  • You must create a default OpenShift Virtualization or OpenShift Container Platform storage class. The purpose of this is to address the unique storage needs of VM workloads and offer optimized performance, reliability, and user experience. If both OpenShift Virtualization and OpenShift Container Platform default storage classes exist, the OpenShift Virtualization class takes precedence when creating VM disks.
Note

To mark a storage class as the default for virtualization workloads, set the annotation storageclass.kubevirt.io/is-default-virt-class to "true".

  • If the storage provisioner supports snapshots, you must associate a VolumeSnapshotClass object with the default storage class.
4.1.2.3.1. About volume and access modes for virtual machine disks

If you use the storage API with known storage providers, the volume and access modes are selected automatically. However, if you use a storage class that does not have a storage profile, you must configure the volume and access mode.

For best results, use the ReadWriteMany (RWX) access mode and the Block volume mode. This is important for the following reasons:

  • ReadWriteMany (RWX) access mode is required for live migration.

  • The Block volume mode performs significantly better than the Filesystem volume mode. This is because the Filesystem volume mode uses more storage layers, including a file system layer and a disk image file. These layers are not necessary for VM disk storage.

    For example, if you use Red Hat OpenShift Data Foundation, Ceph RBD volumes are preferable to CephFS volumes.

Important

You cannot live migrate virtual machines with the following configurations:

  • Storage volume with ReadWriteOnce (RWO) access mode
  • Passthrough features such as GPUs

Set the evictionStrategy field to None for these virtual machines. The None strategy powers down VMs during node reboots.

4.1.3. Live migration requirements

  • Shared storage with ReadWriteMany (RWX) access mode.

  • Sufficient RAM and network bandwidth.

    Note

    You must ensure that there is enough memory request capacity in the cluster to support node drains that result in live migrations. You can determine the approximate required spare memory by using the following calculation: 

    Product of (Maximum number of nodes that can drain in parallel) and (Highest total VM memory request allocations across nodes)

    The default number of migrations that can run in parallel in the cluster is 5.

  • If the virtual machine uses a host model CPU, the nodes must support the virtual machine’s host model CPU.
  • A dedicated Multus network for live migration is highly recommended. A dedicated network minimizes the effects of network saturation on tenant workloads during migration.

4.1.4. Physical resource overhead requirements

OpenShift Virtualization is an add-on to OpenShift Container Platform and imposes additional overhead that you must account for when planning a cluster. Each cluster machine must accommodate the following overhead requirements in addition to the OpenShift Container Platform requirements. Oversubscribing the physical resources in a cluster can affect performance.

Important

The numbers noted in this documentation are based on Red Hat’s test methodology and setup. These numbers can vary based on your own individual setup and environments.

Memory overhead

Calculate the memory overhead values for OpenShift Virtualization by using the equations below.

Cluster memory overhead

Memory overhead per infrastructure node ≈ 150 MiB

Memory overhead per worker node ≈ 360 MiB

Additionally, OpenShift Virtualization environment resources require a total of 2179 MiB of RAM that is spread across all infrastructure nodes.

Virtual machine memory overhead

Memory overhead per virtual machine ≈ (1.002 × requested memory) \
              + 218 MiB \ 1
              + 8 MiB × (number of vCPUs) \ 2
              + 16 MiB × (number of graphics devices) \ 3
              + (additional memory overhead) 4

1
Required for the processes that run in the virt-launcher pod.
2
Number of virtual CPUs requested by the virtual machine.
3
Number of virtual graphics cards requested by the virtual machine.
4
Additional memory overhead:
  • If your environment includes a Single Root I/O Virtualization (SR-IOV) network device or a Graphics Processing Unit (GPU), allocate 1 GiB additional memory overhead for each device.
  • If Secure Encrypted Virtualization (SEV) is enabled, add 256 MiB.
  • If Trusted Platform Module (TPM) is enabled, add 53 MiB.
CPU overhead

Calculate the cluster processor overhead requirements for OpenShift Virtualization by using the equation below. The CPU overhead per virtual machine depends on your individual setup.

Cluster CPU overhead

CPU overhead for infrastructure nodes ≈ 4 cores

OpenShift Virtualization increases the overall utilization of cluster level services such as logging, routing, and monitoring. To account for this workload, ensure that nodes that host infrastructure components have capacity allocated for 4 additional cores (4000 millicores) distributed across those nodes. 

CPU overhead for worker nodes ≈ 2 cores + CPU overhead per virtual machine

Each worker node that hosts virtual machines must have capacity for 2 additional cores (2000 millicores) for OpenShift Virtualization management workloads in addition to the CPUs required for virtual machine workloads.

Virtual machine CPU overhead

If dedicated CPUs are requested, there is a 1:1 impact on the cluster CPU overhead requirement. Otherwise, there are no specific rules about how many CPUs a virtual machine requires.

Storage overhead

Use the guidelines below to estimate storage overhead requirements for your OpenShift Virtualization environment.

Cluster storage overhead

Aggregated storage overhead per node ≈ 10 GiB

10 GiB is the estimated on-disk storage impact for each node in the cluster when you install OpenShift Virtualization.

Virtual machine storage overhead

Storage overhead per virtual machine depends on specific requests for resource allocation within the virtual machine. The request could be for ephemeral storage on the node or storage resources hosted elsewhere in the cluster. OpenShift Virtualization does not currently allocate any additional ephemeral storage for the running container itself.

Example

As a cluster administrator, if you plan to host 10 virtual machines in the cluster, each with 1 GiB of RAM and 2 vCPUs, the memory impact across the cluster is 11.68 GiB. The estimated on-disk storage impact for each node in the cluster is 10 GiB and the CPU impact for worker nodes that host virtual machine workloads is a minimum of 2 cores.

4.1.5. Single-node OpenShift differences

You can install OpenShift Virtualization on single-node OpenShift.

However, you should be aware that Single-node OpenShift does not support the following features:

  • High availability
  • Pod disruption
  • Live migration
  • Virtual machines or templates that have an eviction strategy configured

Additional resources

4.1.6. Object maximums

You must consider the following tested object maximums when planning your cluster:

4.1.7. Cluster high-availability options

You can configure one of the following high-availability (HA) options for your cluster:

  • Automatic high availability for installer-provisioned infrastructure (IPI) is available by deploying machine health checks.

    Note

    In OpenShift Container Platform clusters installed using installer-provisioned infrastructure and with a properly configured MachineHealthCheck resource, if a node fails the machine health check and becomes unavailable to the cluster, it is recycled. What happens next with VMs that ran on the failed node depends on a series of conditions. See Run strategies for more detailed information about the potential outcomes and how run strategies affect those outcomes.

  • Automatic high availability for both IPI and non-IPI is available by using the Node Health Check Operator on the OpenShift Container Platform cluster to deploy the NodeHealthCheck controller. The controller identifies unhealthy nodes and uses a remediation provider, such as the Self Node Remediation Operator or Fence Agents Remediation Operator, to remediate the unhealthy nodes. For more information on remediation, fencing, and maintaining nodes, see the Workload Availability for Red Hat OpenShift documentation.

  • High availability for any platform is available by using either a monitoring system or a qualified human to monitor node availability. When a node is lost, shut it down and run oc delete node <lost_node>.

    Note

    Without an external monitoring system or a qualified human monitoring node health, virtual machines lose high availability.

4.2. Installing OpenShift Virtualization

Install OpenShift Virtualization to add virtualization functionality to your OpenShift Container Platform cluster.

Important

If you install OpenShift Virtualization in a restricted environment with no internet connectivity, you must configure Operator Lifecycle Manager (OLM) for restricted networks.

If you have limited internet connectivity, you can configure proxy support in OLM to access the OperatorHub.

4.2.1. Installing the OpenShift Virtualization Operator

Install the OpenShift Virtualization Operator by using the OpenShift Container Platform web console or the command line.

4.2.1.1. Installing the OpenShift Virtualization Operator by using the web console

You can deploy the OpenShift Virtualization Operator by using the OpenShift Container Platform web console.

Prerequisites

  • Install OpenShift Container Platform 4.15 on your cluster.
  • Log in to the OpenShift Container Platform web console as a user with cluster-admin permissions.

Procedure

  1. From the Administrator perspective, click Operators OperatorHub.
  2. In the Filter by keyword field, type Virtualization.
  3. Select the OpenShift Virtualization Operator tile with the Red Hat source label.
  4. Read the information about the Operator and click Install.

  5. On the Install Operator page:

    1. Select stable from the list of available Update Channel options. This ensures that you install the version of OpenShift Virtualization that is compatible with your OpenShift Container Platform version.

    2. For Installed Namespace, ensure that the Operator recommended namespace option is selected. This installs the Operator in the mandatory openshift-cnv namespace, which is automatically created if it does not exist.

      Warning

      Attempting to install the OpenShift Virtualization Operator in a namespace other than openshift-cnv causes the installation to fail.

    3. For Approval Strategy, it is highly recommended that you select Automatic, which is the default value, so that OpenShift Virtualization automatically updates when a new version is available in the stable update channel.

      While it is possible to select the Manual approval strategy, this is inadvisable because of the high risk that it presents to the supportability and functionality of your cluster. Only select Manual if you fully understand these risks and cannot use Automatic.

      Warning

      Because OpenShift Virtualization is only supported when used with the corresponding OpenShift Container Platform version, missing OpenShift Virtualization updates can cause your cluster to become unsupported.

  6. Click Install to make the Operator available to the openshift-cnv namespace.
  7. When the Operator installs successfully, click Create HyperConverged.
  8. Optional: Configure Infra and Workloads node placement options for OpenShift Virtualization components.
  9. Click Create to launch OpenShift Virtualization.

Verification

  • Navigate to the Workloads Pods page and monitor the OpenShift Virtualization pods until they are all Running. After all the pods display the Running state, you can use OpenShift Virtualization.

4.2.1.2. Installing the OpenShift Virtualization Operator by using the command line

Subscribe to the OpenShift Virtualization catalog and install the OpenShift Virtualization Operator by applying manifests to your cluster.

4.2.1.2.1. Subscribing to the OpenShift Virtualization catalog by using the CLI

Before you install OpenShift Virtualization, you must subscribe to the OpenShift Virtualization catalog. Subscribing gives the openshift-cnv namespace access to the OpenShift Virtualization Operators.

To subscribe, configure Namespace, OperatorGroup, and Subscription objects by applying a single manifest to your cluster.

Prerequisites

  • Install OpenShift Container Platform 4.15 on your cluster.
  • Install the OpenShift CLI (oc).
  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a YAML file that contains the following manifest: 

    apiVersion: v1
kind: Namespace
metadata:
  name: openshift-cnv
---
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: kubevirt-hyperconverged-group
  namespace: openshift-cnv
spec:
  targetNamespaces:
    - openshift-cnv
---
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: hco-operatorhub
  namespace: openshift-cnv
spec:
  source: redhat-operators
  sourceNamespace: openshift-marketplace
  name: kubevirt-hyperconverged
  startingCSV: kubevirt-hyperconverged-operator.v4.15.8
  channel: "stable" 1
    1
    Using the stable channel ensures that you install the version of OpenShift Virtualization that is compatible with your OpenShift Container Platform version.

  2. Create the required Namespace, OperatorGroup, and Subscription objects for OpenShift Virtualization by running the following command: 

    $ oc apply -f <file name>.yaml
Note

You can configure certificate rotation parameters in the YAML file.

4.2.1.2.2. Deploying the OpenShift Virtualization Operator by using the CLI

You can deploy the OpenShift Virtualization Operator by using the oc CLI.

Prerequisites

  • Subscribe to the OpenShift Virtualization catalog in the openshift-cnv namespace.
  • Log in as a user with cluster-admin privileges.

Procedure

  1. Create a YAML file that contains the following manifest: 

    apiVersion: hco.kubevirt.io/v1beta1
kind: HyperConverged
metadata:
  name: kubevirt-hyperconverged
  namespace: openshift-cnv
spec:

  2. Deploy the OpenShift Virtualization Operator by running the following command: 

    $ oc apply -f <file_name>.yaml

Verification

  • Ensure that OpenShift Virtualization deployed successfully by watching the PHASE of the cluster service version (CSV) in the openshift-cnv namespace. Run the following command: 

    $ watch oc get csv -n openshift-cnv

    The following output displays if deployment was successful:

    Example output

    NAME                                      DISPLAY                    VERSION   REPLACES   PHASE
kubevirt-hyperconverged-operator.v4.15.8   OpenShift Virtualization   4.15.8                Succeeded

4.2.2. Next steps

  • The hostpath provisioner is a local storage provisioner designed for OpenShift Virtualization. If you want to configure local storage for virtual machines, you must enable the hostpath provisioner first.

4.3. Uninstalling OpenShift Virtualization

You uninstall OpenShift Virtualization by using the web console or the command line interface (CLI) to delete the OpenShift Virtualization workloads, the Operator, and its resources.

4.3.1. Uninstalling OpenShift Virtualization by using the web console

You uninstall OpenShift Virtualization by using the web console to perform the following tasks:

  1. Delete the HyperConverged CR.
  2. Delete the OpenShift Virtualization Operator.
  3. Delete the openshift-cnv namespace.
  4. Delete the OpenShift Virtualization custom resource definitions (CRDs).
Important

You must first delete all virtual machines, and virtual machine instances.

You cannot uninstall OpenShift Virtualization while its workloads remain on the cluster.

4.3.1.1. Deleting the HyperConverged custom resource

To uninstall OpenShift Virtualization, you first delete the HyperConverged custom resource (CR).

Prerequisites

  • You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions.

Procedure

  1. Navigate to the Operators Installed Operators page.
  2. Select the OpenShift Virtualization Operator.
  3. Click the OpenShift Virtualization Deployment tab.
  4. Click the Options menu kebab beside kubevirt-hyperconverged and select Delete HyperConverged.
  5. Click Delete in the confirmation window.

4.3.1.2. Deleting Operators from a cluster using the web console

Cluster administrators can delete installed Operators from a selected namespace by using the web console.

Prerequisites

  • You have access to an OpenShift Container Platform cluster web console using an account with cluster-admin permissions.

Procedure

  1. Navigate to the Operators Installed Operators page.
  2. Scroll or enter a keyword into the Filter by name field to find the Operator that you want to remove. Then, click on it.

  3. On the right side of the Operator Details page, select Uninstall Operator from the Actions list.

    An Uninstall Operator? dialog box is displayed.

  4. Select Uninstall to remove the Operator, Operator deployments, and pods. Following this action, the Operator stops running and no longer receives updates.

    Note

    This action does not remove resources managed by the Operator, including custom resource definitions (CRDs) and custom resources (CRs). Dashboards and navigation items enabled by the web console and off-cluster resources that continue to run might need manual clean up. To remove these after uninstalling the Operator, you might need to manually delete the Operator CRDs.

4.3.1.3. Deleting a namespace using the web console

You can delete a namespace by using the OpenShift Container Platform web console.

Prerequisites

  • You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions.

Procedure

  1. Navigate to Administration Namespaces.
  2. Locate the namespace that you want to delete in the list of namespaces.
  3. On the far right side of the namespace listing, select Delete Namespace from the Options menu kebab .
  4. When the Delete Namespace pane opens, enter the name of the namespace that you want to delete in the field.
  5. Click Delete.

4.3.1.4. Deleting OpenShift Virtualization custom resource definitions

You can delete the OpenShift Virtualization custom resource definitions (CRDs) by using the web console.

Prerequisites

  • You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions.

Procedure

  1. Navigate to Administration CustomResourceDefinitions.
  2. Select the Label filter and enter operators.coreos.com/kubevirt-hyperconverged.openshift-cnv in the Search field to display the OpenShift Virtualization CRDs.
  3. Click the Options menu kebab beside each CRD and select Delete CustomResourceDefinition.

4.3.2. Uninstalling OpenShift Virtualization by using the CLI

You can uninstall OpenShift Virtualization by using the OpenShift CLI (oc).

Prerequisites

  • You have access to an OpenShift Container Platform cluster using an account with cluster-admin permissions.
  • You have installed the OpenShift CLI (oc).
  • You have deleted all virtual machines and virtual machine instances. You cannot uninstall OpenShift Virtualization while its workloads remain on the cluster.

Procedure

  1. Delete the HyperConverged custom resource: 

    $ oc delete HyperConverged kubevirt-hyperconverged -n openshift-cnv

  2. Delete the OpenShift Virtualization Operator subscription: 

    $ oc delete subscription kubevirt-hyperconverged -n openshift-cnv

  3. Delete the OpenShift Virtualization ClusterServiceVersion resource: 

    $ oc delete csv -n openshift-cnv -l operators.coreos.com/kubevirt-hyperconverged.openshift-cnv

  4. Delete the OpenShift Virtualization namespace: 

    $ oc delete namespace openshift-cnv

  5. List the OpenShift Virtualization custom resource definitions (CRDs) by running the oc delete crd command with the dry-run option: 

    $ oc delete crd --dry-run=client -l operators.coreos.com/kubevirt-hyperconverged.openshift-cnv

    Example output

    customresourcedefinition.apiextensions.k8s.io "cdis.cdi.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "hostpathprovisioners.hostpathprovisioner.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "hyperconvergeds.hco.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "kubevirts.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "networkaddonsconfigs.networkaddonsoperator.network.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "ssps.ssp.kubevirt.io" deleted (dry run)
customresourcedefinition.apiextensions.k8s.io "tektontasks.tektontasks.kubevirt.io" deleted (dry run)

  6. Delete the CRDs by running the oc delete crd command without the dry-run option: 

    $ oc delete crd -l operators.coreos.com/kubevirt-hyperconverged.openshift-cnv

Additional resources

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