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Creating virtual machines

Use one of these procedures to create a virtual machine:

Do not create virtual machines in openshift-* namespaces. Instead, create a new namespace or use an existing namespace without the openshift prefix.

Running the virtual machine wizard to create a virtual machine

The web console features an interactive wizard that guides you through General, Networking, Storage, Advanced, and Review steps to simplify the process of creating virtual machines. All required fields are marked by a *. When the required fields are completed, you can review and create your virtual machine.

Network interface controllers (NICs) and storage disks can be created and attached to virtual machines after they have been created.

Bootable Disk

If either URL or Container are selected as the Source in the General step, a rootdisk disk is created and attached to the virtual machine as the Bootable Disk. You can modify the rootdisk but you cannot remove it.

A Bootable Disk is not required for virtual machines provisioned from a PXE source if there are no disks attached to the virtual machine. If one or more disks are attached to the virtual machine, you must select one as the Bootable Disk.

Prerequisites

  • When you create your virtual machine using the wizard, your virtual machine’s storage medium must support Read-Write-Many (RWX) PVCs.

Procedure

  1. Click Workloads → Virtualization from the side menu.

  2. Click the Virtual Machines tab.

  3. Click Create Virtual Machine and select New with Wizard.

  4. Fill in all required fields in the General step. Selecting a Template automatically fills in these fields.

  5. Click Next to progress to the Networking step. A nic0 NIC is attached by default.

    1. Optional: Click Add Network Interface to create additional NICs.

    2. Optional: You can remove any or all NICs by clicking the Options menu kebab and selecting Delete. A virtual machine does not need a NIC attached to be created. NICs can be created after the virtual machine has been created.

  6. Click Next to progress to the Storage screen.

    1. Optional: Click Add Disk to create additional disks. These disks can be removed by clicking the Options menu kebab and selecting Delete.

    2. Optional: Click the Options menu kebab to edit the disk and save your changes.

  7. Click Review and Create. The Results screen displays the JSON configuration file for the virtual machine.

The virtual machine is listed in the Virtual Machines tab.

Refer to the virtual machine wizard fields section when running the web console wizard.

Virtual machine wizard fields

Name Parameter Description

Template

Template from which to create the virtual machine. Selecting a template will automatically complete other fields.

Source

PXE

Provision virtual machine from PXE menu. Requires a PXE-capable NIC in the cluster.

URL

Provision virtual machine from an image available from an HTTP or S3 endpoint.

Container

Provision virtual machine from a bootable operating system container located in a registry accessible from the cluster. Example: kubevirt/cirros-registry-disk-demo.

Disk

Provision virtual machine from a disk.

Operating System

The primary operating system that is selected for the virtual machine.

Flavor

small, medium, large, tiny, Custom

Presets that determine the amount of CPU and memory allocated to the virtual machine. The presets displayed for Flavor are determined by the operating system.

Memory

Size in GiB of the memory allocated to the virtual machine.

CPUs

The amount of CPU allocated to the virtual machine.

Workload Profile

High Performance

A virtual machine configuration that is optimized for high-performance workloads.

Server

A profile optimized to run server workloads.

Desktop

A virtual machine configuration for use on a desktop.

Name

The name can contain lowercase letters (a-z), numbers (0-9), and hyphens (-), up to a maximum of 253 characters. The first and last characters must be alphanumeric. The name must not contain uppercase letters, spaces, periods (.), or special characters.

Description

Optional description field.

Start virtual machine on creation

Select to automatically start the virtual machine upon creation.

Cloud-init fields

Name Description

Hostname

Sets a specific hostname for the virtual machine.

Authenticated SSH Keys

The user’s public key that is copied to ~/.ssh/authorized_keys on the virtual machine.

Custom script

Replaces other options with a field in which you paste a custom cloud-init script.

CD-ROM fields

Source Description

Container

Specify the container path. For example: kubevirt/fedora-registry-disk: latest.

URL

Specify the URL path and size in GiB. Then, select the storage class for this URL from the drop-down list.

Attach Disk

Select the virtual machine disk that you want to attach.

Networking fields

Name Description

Name

Name for the network interface controller.

Model

Indicates the model of the network interface controller. Supported values are e1000e and virtio.

Network

List of available network attachment definitions.

Type

List of available binding methods. For the default pod network, masquerade is the only recommended binding method. For secondary networks, use the bridge binding method. The masquerade method is not supported for non-default networks.

MAC Address

MAC address for the network interface controller. If a MAC address is not specified, one is assigned automatically.

Storage fields

Name Description

Source

Select a blank disk for the virtual machine or choose from the options available: URL, Container, Attach Cloned Disk, or Attach Disk. To select an existing disk and attach it to the virtual machine, choose Attach Cloned Disk or Attach Disk from a list of available persistent volume claims (PVCs).

Name

Name of the disk. The name can contain lowercase letters (a-z), numbers (0-9), hyphens (-), and periods (.), up to a maximum of 253 characters. The first and last characters must be alphanumeric. The name must not contain uppercase letters, spaces, or special characters.

Size (GiB)

Size, in GiB, of the disk.

Interface

Type of disk device. Supported interfaces are virtIO, SATA, and SCSI.

Storage Class

The storage class that is used to create the disk.

Advanced → Volume Mode

Defines whether the persistent volume uses a formatted file system or raw block state. Default is Filesystem.

Advanced → Access Mode

Access mode of the persistent volume. Supported access modes are ReadWriteOnce, ReadOnlyMany, and ReadWriteMany.

Advanced storage settings

The following advanced storage settings are available for Blank, Import via URL, and Clone existing PVC disks. These parameters are optional. If you do not specify these parameters, the system uses the default values from the kubevirt-storage-class-defaults config map.

Name Parameter Description

Volume Mode

Filesystem

Stores the virtual disk on a file system-based volume.

Block

Stores the virtual disk directly on the block volume. Only use Block if the underlying storage supports it.

Access Mode

Single User (RWO)

The disk can be mounted as read/write by a single node.

Shared Access (RWX)

The disk can be mounted as read/write by many nodes.

This is required for some features, such as live migration of virtual machines between nodes.

Read Only (ROX)

The disk can be mounted as read-only by many nodes.

For more information on the kubevirt-storage-class-defaults config map, see Storage defaults for data volumes.

Pasting in a pre-configured YAML file to create a virtual machine

Create a virtual machine by writing or pasting a YAML configuration file. A valid example virtual machine configuration is provided by default whenever you open the YAML edit screen.

If your YAML configuration is invalid when you click Create, an error message indicates the parameter in which the error occurs. Only one error is shown at a time.

Navigating away from the YAML screen while editing cancels any changes to the configuration you have made.
Procedure

  1. Click Workloads → Virtualization from the side menu.

  2. Click the Virtual Machines tab.

  3. Click Create Virtual Machine and select New from YAML.

  4. Write or paste your virtual machine configuration in the editable window.

    1. Alternatively, use the example virtual machine provided by default in the YAML screen.

  5. Optional: Click Download to download the YAML configuration file in its present state.

  6. Click Create to create the virtual machine.

The virtual machine is listed in the Virtual Machines tab.

Using the CLI to create a virtual machine

You can create a virtual machine from a virtualMachine manifest.

Procedure

  1. Edit the VirtualMachine manifest for your VM. For example, the following manifest configures a Red Hat Enterprise Linux (RHEL) VM:

    Example manifest for a RHEL VM 
    apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  labels:
    app: <vm_name> (1)
  name: <vm_name>
spec:
  dataVolumeTemplates:
  - apiVersion: cdi.kubevirt.io/v1beta1
    kind: DataVolume
    metadata:
      name: <vm_name>
    spec:
      sourceRef:
        kind: DataSource
        name: rhel9
        namespace: openshift-virtualization-os-images
      storage:
        resources:
          requests:
            storage: 30Gi
  running: false
  template:
    metadata:
      labels:
        kubevirt.io/domain: <vm_name>
    spec:
      domain:
        cpu:
          cores: 1
          sockets: 2
          threads: 1
        devices:
          disks:
          - disk:
              bus: virtio
            name: rootdisk
          - disk:
              bus: virtio
            name: cloudinitdisk
          interfaces:
          - masquerade: {}
            name: default
          rng: {}
        features:
          smm:
            enabled: true
        firmware:
          bootloader:
            efi: {}
        resources:
          requests:
            memory: 8Gi
      evictionStrategy: LiveMigrate
      networks:
      - name: default
        pod: {}
      volumes:
      - dataVolume:
          name: <vm_name>
        name: rootdisk
      - cloudInitNoCloud:
          userData: |-
            #cloud-config
            user: cloud-user
            password: '<password>' (2)
            chpasswd: { expire: False }
        name: cloudinitdisk
    1 Specify the name of the virtual machine.
    2 Specify the password for cloud-user.

  2. Create a virtual machine by using the manifest file:

    $ oc create -f <vm_manifest_file>.yaml

  3. Optional: Start the virtual machine:

    $ virtctl start <vm_name>

Virtual machine storage volume types

Storage volume type Description

ephemeral

A local copy-on-write (COW) image that uses a network volume as a read-only backing store. The backing volume must be a PersistentVolumeClaim. The ephemeral image is created when the virtual machine starts and stores all writes locally. The ephemeral image is discarded when the virtual machine is stopped, restarted, or deleted. The backing volume (PVC) is not mutated in any way.

persistentVolumeClaim

Attaches an available PV to a virtual machine. Attaching a PV allows for the virtual machine data to persist between sessions.

Importing an existing virtual machine disk into a PVC by using CDI and attaching the PVC to a virtual machine instance is the recommended method for importing existing virtual machines into OpenShift Container Platform. There are some requirements for the disk to be used within a PVC.

dataVolume

Data volumes build on the persistentVolumeClaim disk type by managing the process of preparing the virtual machine disk via an import, clone, or upload operation. VMs that use this volume type are guaranteed not to start until the volume is ready.

Specify type: dataVolume or type: "". If you specify any other value for type, such as persistentVolumeClaim, a warning is displayed, and the virtual machine does not start.

cloudInitNoCloud

Attaches a disk that contains the referenced cloud-init NoCloud data source, providing user data and metadata to the virtual machine. A cloud-init installation is required inside the virtual machine disk.

containerDisk

References an image, such as a virtual machine disk, that is stored in the container image registry. The image is pulled from the registry and attached to the virtual machine as a disk when the virtual machine is launched.

A containerDisk volume is not limited to a single virtual machine and is useful for creating large numbers of virtual machine clones that do not require persistent storage.

Only RAW and QCOW2 formats are supported disk types for the container image registry. QCOW2 is recommended for reduced image size.

A containerDisk volume is ephemeral. It is discarded when the virtual machine is stopped, restarted, or deleted. A containerDisk volume is useful for read-only file systems such as CD-ROMs or for disposable virtual machines.

emptyDisk

Creates an additional sparse QCOW2 disk that is tied to the life-cycle of the virtual machine interface. The data survives guest-initiated reboots in the virtual machine but is discarded when the virtual machine stops or is restarted from the web console. The empty disk is used to store application dependencies and data that otherwise exceeds the limited temporary file system of an ephemeral disk.

The disk capacity size must also be provided.

About RunStrategies for virtual machines

A RunStrategy for virtual machines determines a virtual machine instance’s (VMI) behavior, depending on a series of conditions. The spec.runStrategy setting exists in the virtual machine configuration process as an alternative to the spec.running setting. The spec.runStrategy setting allows greater flexibility for how VMIs are created and managed, in contrast to the spec.running setting with only true or false responses. However, the two settings are mutually exclusive. Only either spec.running or spec.runStrategy can be used. An error occurs if both are used.

There are four defined RunStrategies.

Always

A VMI is always present when a virtual machine is created. A new VMI is created if the original stops for any reason, which is the same behavior as spec.running: true.

RerunOnFailure

A VMI is re-created if the previous instance fails due to an error. The instance is not re-created if the virtual machine stops successfully, such as when it shuts down.

Manual

The start, stop, and restart virtctl client commands can be used to control the VMI’s state and existence.

Halted

No VMI is present when a virtual machine is created, which is the same behavior as spec.running: false.

Different combinations of the start, stop and restart virtctl commands affect which RunStrategy is used.

The following table follows a VM’s transition from different states. The first column shows the VM’s initial RunStrategy. Each additional column shows a virtctl command and the new RunStrategy after that command is run.

Initial RunStrategy start stop restart

Always

-

Halted

Always

RerunOnFailure

-

Halted

RerunOnFailure

Manual

Manual

Manual

Manual

Halted

Always

-

-

In OpenShift Virtualization clusters installed using installer-provisioned infrastructure, when a node fails the MachineHealthCheck and becomes unavailable to the cluster, VMs with a RunStrategy of Always or RerunOnFailure are rescheduled on a new node.

 
apiVersion: kubevirt.io/v1alpha3
kind: VirtualMachine
spec:
  RunStrategy: Always (1)
  template:
...
1 The VMI’s current RunStrategy setting.

Additional resources