Importing a snapshot into Kubernetes

How to import a CSI VolumeSnapshot in Kubernetes

Using CSI VolumeSnapshots is a powerful tool for managing persistent volumes, creating clones or restoring to a previous state. You can create VolumeSnapshots using Kubernetes (see create snapshot) and use those snapshots within your cluster. However sometimes it is necessary to import an already existing VolumeSnapshot that was created outside your cluster, into your Kubernetes cluster.

This runbook describes how this works and shows examples on how to easily do this using acloud-toolkit snapshot import.

Manually importing VolumeSnapshots

First you need to find the id of your snapshot in your backend storage, such as AWS. This is the ID of the snapshot. For AWS, this looks like snap-027df45af20ee07c6.

Preparing the VolumesnapshotContent

We are going to construct the VolumesnapshotContent resource for Kubernetes.

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotContent
metadata:
  name: snapcontent-<name>
spec:
  deletionPolicy: Retain
  driver: <your-csi-driver>
  source:
    snapshotHandle: <snapshot-id>
  volumeSnapshotClassName: <your-csi-volumesnapshotclass-name>
  volumeSnapshotRef:
    apiVersion: snapshot.storage.k8s.io/v1
    kind: VolumeSnapshot
    name: <name-of-snapshot>
    namespace: <namespace-of-snapshot>

A few important things to note here:

• You need to enter your CSI Driver information for the snapshots. You can retrieve this by using kubectl get volumesnapshotclasses. Use the DRIVER value for spec.driver and the NAME value for spec.volumeSnapshotClassName.

• The spec.volumeSnapshotRef is the name and namespace we will be using to create the VolumeSnapshot resource in your cluster, at the next step. Make sure these do not exist yet and are unique within your cluster.

• And finally, the spec.source.snapshotHandle value will contain the ID of the snapshot in your backend storage (i.g. snap-027df45af20ee07c6).

You can validate the VolumeSnapshotContent has been created in your cluster by using:

kubectl get volumesnapshotcontent

Create the VolumeSnapshot resource

Once the VolumeSnapshotContent has been created, we can insert the VolumeSnapshot resource:

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: <name-of-snapshot>
  namespace: <namespace-of-snapshot>
spec:
  source:
    volumeSnapshotContentName: snapcontent-<name>
  volumeSnapshotClassName: <your-csi-volumesnapshotclass-name>

• Make sure the metadata.name and metadata.namespace equal those used in the spec.volumeSnapshotRef from the VolumeSnapshotContent.

• Use the name of the VolumeSnapshotContent for spec.source.volumeSnapshotContentName and match the spec.volumeSnapshotClassName.

Apply this resource into your cluster and you are now ready to use the VolumeSnapshot to resource persistent volumes within your Kubernetes Cluster!

Using acloud-toolkit

Using the CLI tool acloud-toolkit you are able to quick and easily import a snapshot ID using the above methods, by simply specifying the name and snapshot ID. The CLI will automatically follow the previously detailed steps and create the VolumeSnapshotContent and VolumeSnapshot resources within your Kubernetes cluster.

The acloud-toolkit snapshot import subcommand will by default select your default SnapshotStorageClass and ensure the driver and other settings are configured correctly.

How to use

How to use the snapshot import command:

❯ acloud-toolkit snapshot import -h
This command creates Kubernetes CSI snapshot resources using a snapshot ID from the backend storage, for example AWS EBS, or Ceph RBD.
 
Usage:
  acloud-toolkit snapshot import <snapshot> [flags]
 
Examples:
 
acloud-toolkit snapshot import --name example snap-12345
 
 
Flags:
  -h, --help                            help for import
      --name string                     name of the snapshot
      --namespace string                If present, the namespace scope for this CLI request. Otherwise uses the namespace from the current Kubernetes context
      --snapshot-storage-class string

Example output

In this example, we will be importing the snapshot snap-027df45af20ee07c6 into a VolumeSnapshot called test within our current namespace context.

❯ acloud-toolkit snapshot import --name test snap-027df45af20ee07c6
Creating snapshotcontent "test-66a656c6-f40c-4a20-86a7-07f2a32c9ba1"..
Creating snapshot "test"..
Completed importing snapshot "snap-027df45af20ee07c6" into CSI snapshot test..

You can verify the created resources:

❯ kubectl get volumesnapshot,volumesnapshotcontents.snapshot.storage.k8s.io
NAME                                                   READYTOUSE   SOURCEPVC                    SOURCESNAPSHOTCONTENT                       RESTORESIZE   SNAPSHOTCLASS   SNAPSHOTCONTENT                                    CREATIONTIME   AGE
volumesnapshot.snapshot.storage.k8s.io/test            true                                      test-66a656c6-f40c-4a20-86a7-07f2a32c9ba1   8Gi           ebs             test-66a656c6-f40c-4a20-86a7-07f2a32c9ba1          34m            7s
 
NAME                                                                                             READYTOUSE   RESTORESIZE   DELETIONPOLICY   DRIVER            VOLUMESNAPSHOTCLASS   VOLUMESNAPSHOT   VOLUMESNAPSHOTNAMESPACE    AGE
volumesnapshotcontent.snapshot.storage.k8s.io/test-66a656c6-f40c-4a20-86a7-07f2a32c9ba1          true         8589934592    Retain           ebs.csi.aws.com   ebs                   test             default                    7s