Importing virtual machine images with data volumes

Importing virtual machine images with data volumes

Use the Containerized Data Importer (CDI) to import a virtual machine image into a persistent volume claim (PVC) by using a data volume. You can attach a data volume to a virtual machine for persistent storage.

The virtual machine image can be hosted at an HTTP or HTTPS endpoint, or built into a container disk and stored in a container registry.

When you import a disk image into a PVC, the disk image is expanded to use the full storage capacity that is requested in the PVC. To use this space, the disk partitions and file system(s) in the virtual machine might need to be expanded.

The resizing procedure varies based on the operating system installed on the virtual machine. See the operating system documentation for details.

Prerequisites

If the endpoint requires a TLS certificate, the certificate must be included in a config map in the same namespace as the data volume and referenced in the data volume configuration.
To import a container disk:
- You might need to prepare a container disk from a virtual machine image and store it in your container registry before importing it.
- If the container registry does not have TLS, you must add the registry to the insecureRegistries field of the HyperConverged custom resource before you can import a container disk from it.
You might need to define a storage class or prepare CDI scratch space for this operation to complete successfully.

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

CDI now uses the OKD cluster-wide proxy configuration.

About data volumes

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

Importing a virtual machine image into a persistent volume claim by using a data volume

You can import a virtual machine image into a persistent volume claim (PVC) by using a data volume.

The virtual machine image can be hosted at an HTTP or HTTPS endpoint, or the image can be built into a container disk and stored in a container registry.

To create a virtual machine from an imported virtual machine image, specify the image or container disk endpoint in the VirtualMachine configuration file before you create the virtual machine.

Prerequisites

You have installed the OpenShift CLI (oc).
Your cluster has at least one available persistent volume.
To import a virtual machine image you must have the following:
- A virtual machine disk image in RAW, ISO, or QCOW2 format, optionally compressed by using xz or gz.
- An HTTP endpoint where the image is hosted, along with any authentication credentials needed to access the data source. For example: [http://www.example.com/path/to/data](http://www.example.com/path/to/data)
To import a container disk you must have the following:
- A container disk built from a virtual machine image stored in your container image registry, along with any authentication credentials needed to access the data source. For example: docker://registry.example.com/container-image

Procedure

Optional: If your data source requires authentication credentials, edit the endpoint-secret.yaml file, and apply the updated configuration to the cluster:
```
apiVersion: v1
kind: Secret
metadata:
  name: <endpoint-secret>
  labels:
    app: containerized-data-importer
type: Opaque
data:
  accessKeyId: "" (1)
  secretKey:   "" (2)
```
1 Optional: your key or user name, base64 encoded
2 Optional: your secret or password, base64 encoded
```
$ oc apply -f endpoint-secret.yaml
```

Edit the virtual machine configuration file, specifying the data source for the virtual machine image you want to import. In this example, a Fedora image is imported from an http source:

apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  creationTimestamp: null
  labels:
    kubevirt.io/vm: vm-fedora-datavolume
  name: vm-fedora-datavolume
spec:
  dataVolumeTemplates:
  - metadata:
      creationTimestamp: null
      name: fedora-dv
    spec:
      pvc:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 10Gi
        storageClassName: local
      source:
        http: (1)
          url: "https://download.fedoraproject.org/pub/fedora/linux/releases/33/Cloud/x86_64/images/Fedora-Cloud-Base-33-1.2.x86_64.qcow2" (2)
          secretRef: "" (3)
          certConfigMap: "" (4)
    status: {}
  running: true
  template:
    metadata:
      creationTimestamp: null
      labels:
        kubevirt.io/vm: vm-fedora-datavolume
    spec:
      domain:
        devices:
          disks:
          - disk:
              bus: virtio
            name: datavolumedisk1
        machine:
          type: "" (5)
        resources:
          requests:
            memory: 1.5Gi
      terminationGracePeriodSeconds: 180
      volumes:
      - dataVolume:
          name: fedora-dv
        name: datavolumedisk1
status: {}

1	The source type to import the image from. This example uses an HTTP endpoint. To import a container disk from a registry, replace `http` with `registry`.
2	The source of the virtual machine image you want to import. This example references a virtual machine image at an HTTP endpoint. An example of a container registry endpoint is `url: “docker://kubevirt/fedora-cloud-container-disk-demo:latest”`.
3	The `secretRef` parameter is optional.
4	The `certConfigMap` is required for communicating with servers that use self-signed certificates or certificates not signed by the system CA bundle. The referenced config map must be in the same namespace as the data volume.
5	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.

Create the virtual machine:

$ oc create -f vm-<name>-datavolume.yaml

The oc create command creates the data volume and the virtual machine. The CDI controller creates an underlying PVC with the correct annotation, and the import process begins. When the import completes, the data volume status changes to Succeeded, and the virtual machine is allowed to start.

Data volume provisioning happens in the background, so there is no need to monitor it. You can start the virtual machine, and it will not run until the import is complete.

Verification

The importer pod downloads the virtual machine image or container disk from the specified URL and stores it on the provisioned PV. View the status of the importer pod by running the following command:
```
$ oc get pods
```
Monitor the data volume status until it shows Succeeded by running the following command:
```
$ oc describe dv <datavolume-name> (1)
```
1 The name of the data volume as specified under dataVolumeTemplates.metadata.name in the virtual machine configuration file. In the example configuration above, this is fedora-dv.
To verify that provisioning is complete and that the VMI has started, try accessing its serial console by running the following command:
```
$ virtctl console <vm-fedora-datavolume>
```

Additional resources

Configure preallocation mode to improve write performance for data volume operations.

1	Optional: your key or user name, base64 encoded
2	Optional: your secret or password, base64 encoded