Managing volume snapshots in Kubernetes

You can create a snapshot of a Kubernetes volume to copy its contents at a specific moment in time. This can be useful for restoring volume data in case of data loss.

Volume snapshots are based on custom resource definitions (CRD), so you need to add them to your Kubernetes cluster first.

Prerequisites

A persistent volume claim is created, as described in Dynamically provisioning persistent volumes.

To add custom resource definitions

Run the following commands:

# git clone https://github.com/kubernetes-csi/external-snapshotter/
cd ./external-snapshotter
# git checkout release-5.0
# kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshotclasses.yaml
# kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshotcontents.yaml
# kubectl apply -f client/config/crd/snapshot.storage.k8s.io_volumesnapshots.yaml
# kubectl apply -f deploy/kubernetes/snapshot-controller/rbac-snapshot-controller.yaml -n kube-system
# kubectl apply -f deploy/kubernetes/snapshot-controller/setup-snapshot-controller.yaml -n kube-system

The CSI snapshotter version must not be higher than release-5.0.

These commands will create CRDs for VolumeSnapshotClass, VolumeSnapshotContent, VolumeSnapshot, as well as required ClusterRole, ServiceAccount, ClusterRoleBinding, Role, RoleBinding, and finally the snapshot-controller deployment.

You can check that the required resources are successfully created by using Lens, an easy tool for managing Kubernetes clusters and resources.

To create a volume snapshot

Create the snapshot-class.yaml file that defines the VolumeSnapshotClass object:
```
cat > snapshot-class.yaml <<\EOT
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: mysnapclass
driver: cinder.csi.openstack.org
deletionPolicy: Delete
parameters:
  force-create: "true"
EOT
```
This manifest describes the volume snapshot class mysnapclass with the deletion policy Delete. This policy allows deleting the underlying storage snapshot along with the VolumeSnapshotContent object. To keep both the underlying snapshot and VolumeSnapshotContent when deleting the VolumeSnapshot object, set the deletion policy to Retain.

Create a snapshot class:

$ kubectl apply -f snapshot-class.yaml 
volumesnapshotclass.snapshot.storage.k8s.io/mysnapclass created

Create the snapshot.yaml file that defines the VolumeSnapshot object:
```
cat > snapshot.yaml <<\EOT
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: mysnapshot
spec:
  volumeSnapshotClassName: mysnapclass
  source:
    persistentVolumeClaimName: mypvc
EOT
```
This manifest specifies the volume snapshot mysnapshot that uses the volume snapshot class mysnapclass and creates a snapshot of the previously created volume bound to the persistent volume claim mypvc.
Create a volume snapshot:
```
$ kubectl create -f snapshot.yaml 
volumesnapshot.snapshot.storage.k8s.io/mysnapshot created
```
In the self-service panel, you can find the newly created snapshot mysnapshot on the Compute -> Volumes -> <pv_name> -> Snapshots tab.

To delete a volume snapshot

Run the following command:

$ kubectl delete -f snapshot.yaml 
volumesnapshot.snapshot.storage.k8s.io "mysnapshot" deleted