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Cloning a virtual machine by using a DataVolumeTemplate

You can create a new virtual machine by cloning the PersistentVolumeClaim (PVC) of an existing VM. By including a dataVolumeTemplate in your virtual machine configuration file, you create a new DataVolume from the original PVC.

Cloning operations between different volume modes are not supported. The volumeMode values must match in both the source and target specifications.

For example, if you attempt to clone from a PersistentVolume (PV) with volumeMode: Block to a PV with volumeMode: Filesystem, the operation fails with an error message.

Prerequisites

About DataVolumes

DataVolume objects are custom resources that are provided by the Containerized Data Importer (CDI) project. DataVolumes orchestrate import, clone, and upload operations that are associated with an underlying PersistentVolumeClaim (PVC). DataVolumes are integrated with KubeVirt, and they prevent a virtual machine from being started before the PVC has been prepared.

Creating a new virtual machine from a cloned PersistentVolumeClaim by using a DataVolumeTemplate

You can create a virtual machine that clones the PersistentVolumeClaim (PVC) of an existing virtual machine into a DataVolume. By referencing a dataVolumeTemplate in the virtual machine spec, the source PVC is cloned to a DataVolume, which is then automatically used for the creation of the virtual machine.

When a DataVolume is created as part of the DataVolumeTemplate of a virtual machine, the lifecycle of the DataVolume is then dependent on the virtual machine. If the virtual machine is deleted, the DataVolume and associated PVC are also deleted.
Prerequisites

  • Determine the PVC of an existing virtual machine disk to use. You must power down the virtual machine that is associated with the PVC before you can clone it.

  • Install the OpenShift CLI (oc).

Procedure

  1. Examine the virtual machine you want to clone to identify the name and namespace of the associated PVC.

  2. Create a YAML file for a VirtualMachine object. The following virtual machine example clones my-favorite-vm-disk, which is located in the source-namespace namespace. The 2Gi DataVolume called favorite-clone is created from my-favorite-vm-disk.

    For example:

    apiVersion: kubevirt.io/v1alpha3
kind: VirtualMachine
metadata:
  labels:
    kubevirt.io/vm: vm-dv-clone
  name: vm-dv-clone (1)
spec:
  running: false
  template:
    metadata:
      labels:
        kubevirt.io/vm: vm-dv-clone
    spec:
      domain:
        devices:
          disks:
          - disk:
              bus: virtio
            name: root-disk
        resources:
          requests:
            memory: 64M
      volumes:
      - dataVolume:
          name: favorite-clone
        name: root-disk
  dataVolumeTemplates:
  - metadata:
      name: favorite-clone
    spec:
      pvc:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 2Gi
      source:
        pvc:
          namespace: "source-namespace"
          name: "my-favorite-vm-disk"
    1 The virtual machine to create.

  3. Create the virtual machine with the PVC-cloned DataVolume:

    $ oc create -f <vm-clone-datavolumetemplate>.yaml

Template: DataVolume virtual machine configuration file

example-dv-vm.yaml

apiVersion: kubevirt.io/v1alpha3
kind: VirtualMachine
metadata:
  labels:
    kubevirt.io/vm: example-vm
  name: example-vm
spec:
  dataVolumeTemplates:
  - metadata:
      name: example-dv
    spec:
      pvc:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 1G
      source:
          http:
             url: "" (1)
  running: false
  template:
    metadata:
      labels:
        kubevirt.io/vm: example-vm
    spec:
      domain:
        cpu:
          cores: 1
        devices:
          disks:
          - disk:
              bus: virtio
            name: example-dv-disk
        machine:
          type: q35
        resources:
          requests:
            memory: 1G
      terminationGracePeriodSeconds: 0
      volumes:
      - dataVolume:
          name: example-dv
        name: example-dv-disk
1 The HTTP source of the image you want to import, if applicable.

CDI supported operations matrix

This matrix shows the supported CDI operations for content types against endpoints, and which of these operations requires scratch space.

Content types HTTP HTTPS HTTP basic auth Registry Upload

KubeVirt(QCOW2)

✓ QCOW2
✓ GZ*
✓ XZ*

✓ QCOW2**
✓ GZ*
✓ XZ*

✓ QCOW2
✓ GZ*
✓ XZ*

✓ QCOW2*
□ GZ
□ XZ

✓ QCOW2*
✓ GZ*
✓ XZ*

KubeVirt (RAW)

✓ RAW
✓ GZ
✓ XZ

✓ RAW
✓ GZ
✓ XZ

✓ RAW
✓ GZ
✓ XZ

✓ RAW*
□ GZ
□ XZ

✓ RAW*
✓ GZ*
✓ XZ*

✓ Supported operation

□ Unsupported operation

* Requires scratch space

** Requires scratch space if a custom certificate authority is required