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    Snapshot a PersistentVolume

    You can use the Kubernetes volume snapshot feature for Persistent volumes and dynamic provisioning in your GKE clusters.

    Volume snapshots let you create a copy of your volume at a specific point in time. You can use this copy to bring a volume back to a prior state or to provision a replacement volume.

    You can provision and attach volume snapshots with the following components:

    Requirements

    To use volume snapshots on GKE on AWS, you must have the following:

    • A volume using a Container Storage Interface (CSI) driver that supports snapshots. The Elastic Block Store (EBS) drivers that GKE on AWS uses by default support snapshots.

      For a list of all CSI drivers that support snapshots, see the "Other features" column in Drivers in the Kubernetes documentation.

    • Have an existing PersistentVolumeClaim to use for a snapshot. The PersistentVolume you use for a snapshot source must be managed by a CSI driver. You can verify that you're using a CSI driver by checking that the PersistentVolume spec has a csi section with driver: ebs.csi.aws.com . If your cluster Dynamically provisions PersistentVolumes by the CSI driver as described in the following sections, it's managed by the CSI driver.

    Before you begin

    Create and use a volume snapshot

    The examples in this document show you how to do the following tasks:

    1. Create an example PersistentVolumeClaim and Pod .
    2. Create a VolumeSnapshot .
    3. Restore the volume snapshot .
    4. Verify that the restoration worked .

    To use a volume snapshot, you must complete the following steps:

    1. Create a VolumeSnapshot object to request a snapshot of an existing PersistentVolumeClaim.
    2. Reference the VolumeSnapshot in a PersistentVolumeClaim to restore a volume to that snapshot or create a new volume using the snapshot.

    Create an example PersistentVolumeClaim and Pod

    1. To create the PersistentVolumeClaim object, save the following manifest as example-pvc.yaml :

        apiVersion 
 : 
  
 v1 
 kind 
 : 
  
 PersistentVolumeClaim 
 metadata 
 : 
  
 name 
 : 
  
 example-pvc 
 spec 
 : 
  
 storageClassName 
 : 
  
 standard-rwo 
  
 accessModes 
 : 
  
 - 
  
 ReadWriteOnce 
  
 resources 
 : 
  
 requests 
 : 
  
 storage 
 : 
  
 1Gi

      For spec.storageClassName , you can specify any storage class that uses a supported CSI driver. This example uses the default standard-rwo storage class.

    2. Apply the manifest:

       kubectl  
apply  
-f  
example-pvc.yaml

    3. Create a Pod that writes the current date and time to the volume. To create a Pod, save the following manifest as snapshot-shell.yaml :

        apiVersion 
 : 
  
 v1 
 kind 
 : 
  
 Pod 
 metadata 
 : 
  
 name 
 : 
  
 snapshot-shell 
 spec 
 : 
  
 terminationGracePeriodSeconds 
 : 
  
 10 
  
 containers 
 : 
  
 - 
  
 name 
 : 
  
 linux 
  
 image 
 : 
  
 ubuntu:bionic 
  
 command 
 : 
  
 [ 
 "/bin/sh" 
 ] 
  
 args 
 : 
  
 [ 
 "-c" 
 , 
  
 "echo 
  
 $(date 
  
 -u) 
 >> 
 /data/out.txt" 
 ] 
  
 volumeMounts 
 : 
  
 - 
  
 name 
 : 
  
 snapshot-volume 
  
 mountPath 
 : 
  
 /data 
  
 restartPolicy 
 : 
  
 Never 
  
 volumes 
 : 
  
 - 
  
 name 
 : 
  
 snapshot-volume 
  
 persistentVolumeClaim 
 : 
  
 claimName 
 : 
  
 example-pvc

    4. Apply the manifest:

       kubectl  
apply  
-f  
snapshot-shell.yaml

    5. Check the status of the Pod:

       kubectl  
get  
pod  
snapshot-shell

      It might take some time for the Pod to run and complete. You can run the preceding command until you see an output similar to the following:

       NAME             READY   STATUS      RESTARTS   AGE
snapshot-shell   0/1     Completed   0          24s

    Create a VolumeSnapshot

    A VolumeSnapshot object is a request for a snapshot of an existing PersistentVolumeClaim object. When you create a VolumeSnapshot object, your cluster automatically creates and binds it with a VolumeSnapshotContent object, which is a resource in your cluster like a PersistentVolume object.

    1. Save the following manifest as volumesnapshot.yaml .

        apiVersion 
 : 
  
 snapshot.storage.k8s.io/v1 
 kind 
 : 
  
 VolumeSnapshot 
 metadata 
 : 
  
 name 
 : 
  
 example-snapshot 
 spec 
 : 
  
 source 
 : 
  
 persistentVolumeClaimName 
 : 
  
 example-pvc

    2. Apply the manifest:

       kubectl  
apply  
-f  
volumesnapshot.yaml

      After you create a volume snapshot, your cluster creates a corresponding VolumeSnapshotContent object. This object stores the snapshot and bindings of VolumeSnapshot objects. You do not interact with VolumeSnapshotContents objects directly.

    3. Confirm that your cluster created the VolumeSnapshotContents object:

       kubectl  
get  
volumesnapshotcontents

      The output is similar to the following:

       NAME                                               AGE
snapcontent-cee5fb1f-5427-11ea-a53c-42010a1000da   55s

    Confirm the volume snapshot is ready

    After the volume snapshot content is created, the CSI driver you specified in the VolumeSnapshotClass creates a snapshot on the corresponding storage system. After your cluster creates a snapshot on the storage system and binds it to a VolumeSnapshot object, the snapshot is ready to use. You can check the status by running the following command:

     kubectl  
get  
volumesnapshot  
 \ 
  
-o  
custom-columns = 
 'NAME:.metadata.name,READY:.status.readyToUse'

    If the snapshot is ready to use, the output is similar to the following:

     NAME                    READY
example-snapshot        true

    Restore the volume snapshot

    You can reference a VolumeSnapshot in a PersistentVolumeClaim to provision a new volume with data from an existing volume or restore a volume to a state that you captured in the snapshot.

    To reference a VolumeSnapshot in a PersistentVolumeClaim , add the dataSource field to your PersistentVolumeClaim .

    In this example, you reference the VolumeSnapshot that you created in a new PersistentVolumeClaim and create a Pod that mounts the PersistentVolumeClaim .

    1. Save the following manifest as pvc-restore.yaml :

        apiVersion 
 : 
  
 v1 
 kind 
 : 
  
 PersistentVolumeClaim 
 metadata 
 : 
  
 name 
 : 
  
 pvc-restore 
 spec 
 : 
  
  dataSource 
 : 
  
 name 
 : 
  
 example-snapshot 
  
 kind 
 : 
  
 VolumeSnapshot 
  
 apiGroup 
 : 
  
 snapshot.storage.k8s.io 
  
 storageClassName 
 : 
  
 standard-rwo 
  
 accessModes 
 : 
  
 - 
  
 ReadWriteOnce 
  
 resources 
 : 
  
 requests 
 : 
  
 storage 
 : 
  
 1Gi

    2. Apply the manifest:

       kubectl  
apply  
-f  
pvc-restore.yaml

    3. Launch a temporary Pod that mounts the PVC to the Pod and prints the contents of out.txt to logs.

      Save the following manifest as restore-log.yaml :

        apiVersion 
 : 
  
 v1 
 kind 
 : 
  
 Pod 
 metadata 
 : 
  
 name 
 : 
  
 restore-verify 
 spec 
 : 
  
 volumes 
 : 
  
 - 
  
 name 
 : 
  
 restore-data 
  
 persistentVolumeClaim 
 : 
  
 claimName 
 : 
  
 pvc-restore 
  
 containers 
 : 
  
 - 
  
 name 
 : 
  
 shell-container 
  
 image 
 : 
  
 ubuntu:bionic 
  
 volumeMounts 
 : 
  
 - 
  
 mountPath 
 : 
  
 "/data" 
  
 name 
 : 
  
 restore-data 
  
 command 
 : 
  
 [ 
  
 "/bin/sh" 
  
 ] 
  
 args 
 : 
  
 [ 
 "-c" 
 , 
  
 "cat 
  
 /data/out.txt" 
 , 
  
 "exit" 
 , 
  
 "1" 
 ] 
  
 restartPolicy 
 : 
  
 Never

    4. Apply the manifest:

       kubectl  
apply  
-f  
restore-log.yaml

    Check that the snapshot restored successfully

    The Pod you created in the previous step reads from the snapshot. To view the data from the snapshot, use the kubectl logs command.

     kubectl  
logs  
restore-verify

    The output should include a timestamp from the snapshot.

    Clean up

    To avoid incurring charges for the resources used on this page, follow these steps.

    1. Delete the VolumeSnapshot :

       kubectl  
delete  
volumesnapshot  
example-snapshot

    2. Delete the temporary Pod:

       kubectl  
delete  
-f  
restore-log.yaml

    3. Delete the Pod:

       kubectl  
delete  
-f  
snapshot-shell.yaml

    4. Delete the PersistentVolumeClaim objects:

       kubectl  
delete  
pvc  
example-pvc  
pvc-restore

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