(assuming running Kubernetes local cluster):

_output/bin/snapshot-controller  -kubeconfig=${HOME}/.kube/config

We use /tmp/test in this example as HostPath directory represented by PV.

• Create the directory

  mkdir /tmp/test

• Create PV for it and PVC that binds to it

  kubectl create -f examples/hostpath/pv.yaml
  kubectl create -f examples/hostpath/pvc.yaml

• Simulate a pod that writes some data to the HostPath volume. We do not need a real pod, simple echo is enough. In real life, there would be a pod creating say MySQL database in the volume.

  echo "hello world" > /tmp/test/data

Now we have PVC bound to a PV that contains some data. We want to take snapshot of this data so we can restore the data later.

• Create a Snapshot Third Party Resource

  kubectl create -f examples/hostpath/snapshot.yaml

• Appropriate Kubernetes objects are available and describe the snapshot (output is trimmed for readability):

  kubectl get volumesnapshot,volumesnapshotdata -o yaml
  apiVersion: v1
  items:
  - apiVersion: volumesnapshot.external-storage.k8s.io/v1
    kind: VolumeSnapshot
    metadata:
      labels:
        Timestamp: "1505214128800981201"
      name: snapshot-demo
      namespace: default
    spec:
      persistentVolumeClaimName: hostpath-pvc
      snapshotDataName: k8s-volume-snapshot-d2209d5a-97a9-11e7-b963-5254000ac840
    status:
      conditions:
      - lastTransitionTime: 2017-09-12T11:02:08Z
        message: Snapshot created successfully
        status: "True"
        type: Ready
  - apiVersion: volumesnapshot.external-storage.k8s.io/v1
    kind: VolumeSnapshotData
    metadata:
      name: k8s-volume-snapshot-d2209d5a-97a9-11e7-b963-5254000ac840
      namespace: ""
    spec:
      hostPath:
        snapshot: /tmp/d21782d1-97a9-11e7-b963-5254000ac840.tgz
      persistentVolumeRef:
        kind: PersistentVolume
        name: hostpath-pv
      volumeSnapshotRef:
        kind: VolumeSnapshot
        name: default/snapshot-demo
    status:
      conditions:
        message: Snapshot created successfully
        status: "True"
        type: Ready
  kind: List
  metadata: {}
  resourceVersion: ""
  selfLink: ""

• The snapshot is available on disk as .tgz archive as specified in volumeSnapshotData.spec.hostPath.snapshot. The file contains snapshot of our /tmp/test directory:

  $ tar tzf /tmp/d21782d1-97a9-11e7-b963-5254000ac840.tgz
  test/
  test/data

Unlike exiting PV provisioners that provision blank volume, Snapshot based PV provisioners create volumes based on existing snapshots. Thus new provisioners are needed.

There is a special annotation give to PVCs that request snapshot based PVs. As illustrated in the example, snapshot.alpha.kubernetes.io must point to an existing VolumeSnapshot Object

metadata:
  name:
  namespace:
  annotations:
    snapshot.alpha.kubernetes.io/snapshot: snapshot-demo

• Start provisioner (assuming running Kubernetes local cluster):

  _output/bin/snapshot-provisioner  -kubeconfig=${HOME}/.kube/config

• Create a storage class:

  kubectl create -f examples/hostpath/class.yaml

• Create a PVC that claims a PV based on an existing snapshot

  kubectl create -f examples/hostpath/claim.yaml

• Check that a PV was created

  kubectl get pv,pvc

Snapshots are restored to /tmp/restore.