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Uploading a local disk image to a block storage DataVolume

You can upload a local disk image into a block DataVolume by using the virtctl command-line utility.

In this workflow, you create a local block device to use as a PersistentVolume, associate this block volume with an upload DataVolume, and use virtctl to upload the local disk image into the DataVolume.

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.

About block PersistentVolumes

A block PersistentVolume (PV) is a PV that is backed by a raw block device. These volumes do not have a filesystem and can provide performance benefits for virtual machines by reducing overhead.

Raw block volumes are provisioned by specifying volumeMode: Block in the PV and PersistentVolumeClaim (PVC) specification.

Creating a local block PersistentVolume

Create a local block PersistentVolume (PV) on a node by populating a file and mounting it as a loop device. You can then reference this loop device in a PV configuration as a Block volume and use it as a block device for a virtual machine image.

Procedure

  1. Log in as root to the node on which to create the local PV. This procedure uses node01 for its examples.

  2. Create a file and populate it with null characters so that it can be used as a block device. The following example creates a file loop10 with a size of 2Gb (20 100Mb blocks):

    $ dd if=/dev/zero of=<loop10> bs=100M count=20

  3. Mount the loop10 file as a loop device.

    $ losetup </dev/loop10>d3 <loop10>  (1) (2)
    1 File path where the loop device is mounted.
    2 The file created in the previous step to be mounted as the loop device.

  4. Create a PersistentVolume configuration that references the mounted loop device.

    kind: PersistentVolume
apiVersion: v1
metadata:
  name: <local-block-pv10>
  annotations:
spec:
  local:
    path: </dev/loop10> (1)
  capacity:
    storage: <2Gi>
  volumeMode: Block (2)
  storageClassName: local (3)
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - <node01> (4)
    1 The path of the loop device on the node.
    2 Specifies it is a block PV.
    3 Optional: Set a StorageClass for the PV. If you omit it, the cluster default is used.
    4 The node on which the block device was mounted.

  5. Create the block PV.

    # oc create -f <local-block-pv10.yaml>(1)
    1 The filename of the PersistentVolume created in the previous step.

Creating an upload DataVolume

You can manually create a DataVolume with an upload data source to use for uploading local disk images.

Procedure

  1. Create a DataVolume configuration that specifies spec: source: upload{}:

    apiVersion: cdi.kubevirt.io/v1alpha1
kind: DataVolume
metadata:
  name: <upload-datavolume> (1)
spec:
  source:
      upload: {}
  pvc:
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: <2Gi> (2)
    1 The name of the DataVolume.
    2 The size of the DataVolume. Ensure that this value is greater than or equal to the size of the disk that you upload.

  2. Create the DataVolume by running the following command:

    $ oc create -f <upload-datavolume>.yaml

Uploading a local disk image to a DataVolume

You can use the virtctl CLI utility to upload a local disk image from a client machine to a DataVolume (DV) in your cluster. You can use a DV that already exists in your cluster or create a new DV during this procedure.

After you upload a local disk image, you can add it to a virtual machine.
Prerequisites

  • A virtual machine disk image, in RAW, ISO, or QCOW2 format, optionally compressed by using xz or gz.

  • The kubevirt-virtctl package must be installed on the client machine.

  • The client machine must be configured to trust the OpenShift Container Platform router’s certificate.

Procedure

  1. Identify the following items:

    • The name of the upload DataVolume that you want to use. If this DataVolume does not exist, it is created automatically.

    • The size of the DataVolume, if you want it to be created during the upload procedure. The size must be greater than or equal to the size of the disk image.

    • The file location of the virtual machine disk image that you want to upload.

  2. Upload the disk image by running the virtctl image-upload command. Specify the parameters that you identified in the previous step. For example:

    $ virtctl image-upload dv <datavolume_name> \ (1)
--size=<datavolume_size> \ (2)
--image-path=</path/to/image> \ (3)
    1 The name of the DataVolume.
    2 The size of the DataVolume. For example: --size=500Mi, --size=1G
    3 The file path of the virtual machine disk image.

    • If you do not want to create a new DataVolume, omit the --size parameter and include the --no-create flag.

    • When uploading a disk image to a PVC, the PVC size must be larger than the size of the uncompressed virtual disk.

    • To allow insecure server connections when using HTTPS, use the --insecure parameter. Be aware that when you use the --insecure flag, the authenticity of the upload endpoint is not verified.

  3. Optional. To verify that a DataVolume was created, view all DataVolume objects by running the following command:

    $ oc get dvs

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