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Quick Howto

Start Snapshot Controller

(assuming running Kubernetes local cluster):

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

Prepare a HostPath PV

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

Create a snapshot

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

Check VolumeSnapshot and VolumeSnapshotData are created

  • 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

Snapshot based PV Provisioner

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

HostPath Volume Type

Start PV Provisioner and Storage Class to restore a snapshot to a PV

  • 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

Restore a snapshot to a new PV

  • 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.