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Creating a registry image with a VM disk

The purpose of this document is to show how to create registry image containing a Virtual Machine image that can be imported into a PV.

Prerequisites

Import from registry should be able to consume the same container images as containerDisk. Thus the VM disk image file to be consumed must be located under /disk directory in the container image. The file can be in any of the supported formats : qcow2, raw, archived image file. There are no special naming constraints for the VM disk file.

Import VM disk image file from existing containerDisk images in kubevirt repository

For example vmidisks/fedora25:latest as described in containerDisk

Create a container image with Buildah

Buildah is a tool that facilitates building Open Container Initiative (OCI) container images. More information is available here: Buildah tutorial.

Create a new directory /tmp/vmdisk with the following Docker file and a vm image file (ex: fedora28.qcow2) Create a new container image with the following docker file

cat << END > Dockerfile
FROM kubevirt/container-disk-v1alpha
ADD fedora28.qcow2 /disk
END

Build and push image to a registry. Note: In development environment you can push to

  1. A cluster local cdi-docker-registry-host which hosts docker registry and is accessible within the cluster via cdi-docker-registry-host.cdi. The registry is initialized from cluster-sync flow and is used for functional tests purposes.
  2. Globally accessible registry that is used for image caching and is accessible via registry:5000 host name
buildah bud -t vmidisk/fedora28:latest /tmp/vmdisk
buildah push --tls-verify=false vmidisk/fedora28:latest docker://cdi-docker-registry-host.cdi/fedora28:latest

Create a container image with Docker

Create a Dockerfile with the following content in a new directory /tmp/vmdisk. Add an image file to the same directory (for example fedora28.qcow2)

FROM kubevirt/container-disk-v1alpha
ADD fedora28.qcow2 /disk

Build, tag and push the image:

docker build -t vmdisks/fedora28:latest /tmp/vmdisk
docker push vmdisks/fedora28:latest

Decorate the PVC of the imported containerdisk with additional labels

It is possible to add additional labels to the PVC into which the containerdisk is imported. To do this, add ENV variables prefixed with *_KUBEVIRT_IO_ or KUBEVIRT_IO_ durning the containerdisk build.

For example, when using the following Dockerfile, the imported PVC will receive these additional labels:

  • instancetype.kubevirt.io/default-instancetype: u1.small
  • instancetype.kubevirt.io/default-preference: fedora
FROM kubevirt/container-disk-v1alpha
ADD fedora28.qcow2 /disk

ENV INSTANCETYPE_KUBEVIRT_IO_DEFAULT_INSTANCETYPE u1.small
ENV INSTANCETYPE_KUBEVIRT_IO_DEFAULT_PREFERENCE fedora

For this feature, environment variables were chosen over labels on the image's manifest so they can be accessed with both pull methods pod and node. During imports with pull method node the image's manifest is not accessible by the importer. However, the image's environment variables can still be accessed by the importer's server binary, which is injected into the container responsible for pulling the image.

Import the registry image into a Data volume

Use the following to import a fedora cloud image from docker hub:

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: registry-image-datavolume
spec:
  source:
    registry:
      url: "docker://kubevirt/fedora-cloud-registry-disk-demo"
  storage:
    resources:
      requests:
        storage: 5Gi

Full example is available here: registry-image-pvc

Registry security

Private registry

If your docker registry requires authentication:

Create a Secret in the same namespace as the DataVolume to store user credentials. See endpoint-secret

Add SecretRef to DataVolume spec.

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
...
spec:
  source:
    registry:
      url: "docker://my-private-registry:5000/my-username/my-image"
      secretRef: my-docker-creds
...

TLS certificate configuration

If your registry TLS certificate is not signed by a trusted CA:

Create a ConfigMap in the same namespace as the DataVolume containing all certificates required to trust the registry.

kubectl create configmap my-registry-certs --from-file=my-registry.crt

The ConfigMap may contain multiple entries if necessary. Key name is irrelevant but should have suffix .crt.

Add certConfigMap to DataVolume spec.

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
...
spec:
  source:
    registry:
      url: "docker://my-private-registry-host:5000/my-username/my-image"
      certConfigMap: my-registry-certs
...

Insecure registry

To disable TLS security for a registry:

Add the registry to CDIConfig insecureRegistries in the cdi namespace.

kubectl patch cdi cdi --patch '{"spec": {"config": {"insecureRegistries": ["my-private-registry-host:5000"]}}}' --type merge

Import registry image into a Data volume using node docker cache

We also support import using node pullMethod which is based on the node docker cache. This is useful when registry image is usable via Container.Image but CDI importer is not authorized to access it (e.g. registry.redhat.io requires a pull secret):

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: registry-image-datavolume
spec:
  source:
    registry:
      url: "docker://kubevirt/cirros-container-disk-demo:devel"
      pullMethod: node
  storage:
    resources:
      requests:
        storage: 5Gi

Using this method we also support import from OpenShift imageStream instead of url:

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: registry-image-datavolume
spec:
  source:
    registry:
      imageStream: rhel8-guest-is
      pullMethod: node
  storage:
    resources:
      requests:
        storage: 5Gi

More information on image streams is available here and here.