Importing virtual machine images to block storage with DataVolumes - Container-native virtualization user's guide | Container-native virtualization

About DataVolumes
About block PersistentVolumes
Creating a local block PersistentVolume
Importing a virtual machine image to a block PersistentVolume using DataVolumes
CDI supported operations matrix

You can import an existing virtual machine image into your OpenShift Container Platform cluster. Container-native virtualization uses DataVolumes to automate the import of data and the creation of an underlying PersistentVolumeClaim (PVC).

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 that is installed on the virtual machine. Refer to the operating system documentation for details.

Prerequisites

If you require scratch space according to the CDI supported operations matrix, you must first define a StorageClass or prepare CDI scratch space for this operation to complete successfully.

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 that either write to the disk directly or implement their own storage service.

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

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

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.

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

Importing a virtual machine image to a block PersistentVolume using DataVolumes

You can import an existing virtual machine image into your OpenShift Container Platform cluster. Container-native virtualization uses DataVolumes to automate the importing data and the creation of an underlying PersistentVolumeClaim (PVC). You can then reference the DataVolume in a virtual machine configuration.

Prerequisites

A virtual machine disk image, in RAW, ISO, or QCOW2 format, optionally compressed by using xz or gz.
An HTTP or s3 endpoint where the image is hosted, along with any authentication credentials needed to access the data source
At least one available block PV.

Procedure

If your data source requires authentication credentials, edit the endpoint-secret.yaml file, and apply the updated configuration to the cluster.
1. Edit the endpoint-secret.yaml file with your preferred text editor:
  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
2. Update the secret:
  $ oc apply -f endpoint-secret.yaml

Create a DataVolume configuration that specifies the data source for the image you want to import and volumeMode: Block so that an available block PV is used.

apiVersion: cdi.kubevirt.io/v1alpha1
kind: DataVolume
metadata:
  name: <import-pv-datavolume> (1)
spec:
  storageClassName: local (2)
  source:
      http:
         url: <http://download.fedoraproject.org/pub/fedora/linux/releases/28/Cloud/x86_64/images/Fedora-Cloud-Base-28-1.1.x86_64.qcow2> (3)
         secretRef: <endpoint-secret> (4)
  pvc:
    volumeMode: Block (5)
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: <2Gi>

1	The name of the DataVolume.
2	Optional: Set the storage class or omit it to accept the cluster default.
3	The `HTTP` source of the image to import.
4	Only required if the data source requires authentication.
5	Required for importing to a block PV.

Create the DataVolume to import the virtual machine image.
```
$ oc create -f <import-pv-datavolume.yaml>(1)
```
1 The filename DataVolume created in the previous step.

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*
Archive+	✓ TAR	✓ TAR	✓ TAR	□ TAR	□ TAR

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*

Archive+

✓ TAR

□ TAR

✓ Supported operation

□ Unsupported operation

* Requires scratch space

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

+ Archive does not support block mode DVs

1	File path where the loop device is mounted.
2	The file created in the previous step to be mounted as the loop device.

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