OpenShift Container Platform

Add an image volume to a pod

To mount an Open Container Initiative (OCI)-compliant container image or artifact, use the volume parameter in your pod spec to include a path to the image or artifact, along with an optional pull policy.

You can create the pod directly or use a controlling object, such as a deployment or replica set.

Procedure

Create a YAML file similar to the following.
```
apiVersion: v1
kind: Pod
metadata:
  name: image-volume
spec:
  containers:
  - name: image-volume-container
    command: ["sleep", "infinity"]
    image: debian
    volumeMounts:
    - name: image
      mountPath: /image
  - name: artifact-volume-container
    image: busybox:latest
    command: ["/bin/sh"]
    args:
    - -c
    - trap 'exit 0' TERM INT; sleep infinity & wait
    volumeMounts:
    - name: artifact
      mountPath: /artifact
  volumes:
  - name: image
    image:
      reference: quay.io/crio/busybox:1
      pullPolicy: Always
  - name: artifact
    image:
      reference: quay.io/crio/artifact:singlefile
      pullPolicy: IfNotPresent
```
where:
spec.containers

Specifies the configuration for one or more containers.

spec.containers.volumeMounts

Specifies the name of the volume to mount and where to mount that volume. The first example indicates the container with the name image-volume-container should mount the image volume under the path /image.

spec.volumes

Specifies the storage volumes that are available for the containers to use.

spec.volumes.name

Specifies a name for the volume.

spec.volumes.image

Specifies an OCI container image or artifact that is available on the host machine.

spec.volumes.image.reference

Specifies the path to the OCI object.

spec.volumes.image.pullPolicy
Specifies a pull policy, one of the following options:
If Always, the kubelet always attempts to pull the OCI object. If the pull fails, the kubelet sets the pod to Failed.

If Never, the kubelet never pulls the image and only uses an OCI object. The pod becomes Failed if any layers of the image are not present locally, or if the manifest for that image is not already cached.

If IfNotPresent, the kubelet pulls the OCI object if it is not present. The pod becomes Failed if the OCI object is not present and the pull fails. This is the default.
Create the pod by running the following command:
```
$ oc create -f <file_name>.yaml
```

Verification

Examine the pod to view detailed information about the image pull and mount by using a command similar to the following:

$ oc describe pod <pod_name>

Example output

Name:             image-volume
Namespace:        default
# ...
Containers:
  image-volume-container:
# ...
    Mounts:
      /image from image (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-svtzn (ro)
  artifact-volume-container:
# ...
    Mounts:
      /artifact from artifact (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-svtzn (ro)
# ...
Volumes:
  image:
    Type:        Image (a container image or OCI artifact)
    Reference:   quay.io/crio/busybox:1
    PullPolicy:  Always
  artifact:
    Type:        Image (a container image or OCI artifact)
    Reference:   quay.io/crio/artifact:singlefile
    PullPolicy:  IfNotPresent
# ...
Events:
  Type    Reason          Age                From               Message
  ----    ------          ----               ----               -------
# ...
  Normal  Pulling         10s (x3 over 15s)  kubelet            Pulling image "quay.io/crio/busybox:1"
  Normal  Pulled          10s                kubelet            Successfully pulled image "quay.io/crio/busybox:1" in 555ms (555ms including waiting). Image size: 1468102 bytes.
# ...
  Normal  Pulling         15s                kubelet            Pulling image "quay.io/crio/artifact:singlefile"
  Normal  Pulled          13s                kubelet            Successfully pulled image "quay.io/crio/artifact:singlefile" in 1.493s (1.493s including waiting). Image size: 14 bytes.
# ...

The Containers stanza shows that the two containers were created with the configured volume mounts.
The Volumes stanza shows that the two volumes were created.
The Events stanza shows that the images in the volumes were pulled.