4.3. CSI volume snapshots

1. Create a file with the VolumeSnapshotClass object described by the following YAML:

   volumesnapshotclass.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshotClass 

   1

   
   metadata:
     name: csi-hostpath-snap
   driver: hostpath.csi.k8s.io
   deletionPolicy: Delete

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   1

   Allows you to specify different attributes belonging to a volume snapshot.

2. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshotclass.yaml

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3. Create a VolumeSnapshot object:

   volumesnapshot-dynamic.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: mysnap
   spec:
     volumeSnapshotClassName: csi-hostpath-snap 

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     source:
       persistentVolumeClaimName: myclaim 

   2

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   1

   The request for a particular class by the volume snapshot. If volumeSnapshotClassName is empty, then no snapshot is created.

   2

   The name of the PersistentVolumeClaim object bound to a persistent volume. This defines what you want to create a snapshot of. Required for dynamically provisioning a snapshot.

4. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshot-dynamic.yaml

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1. Provide a value for the volumeSnapshotContentName parameter as the source for the snapshot, in addition to defining volume snapshot class as shown above.

   volumesnapshot-manual.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: snapshot-demo
   spec:
     source:
       volumeSnapshotContentName: mycontent 

   1

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   1

   The volumeSnapshotContentName parameter is required for pre-provisioned snapshots.

2. Create the object you saved in the previous step by entering the following command:

   $ oc create -f volumesnapshot-manual.yaml

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1. To display details about the volume snapshot that was created, enter the following command:

   $ oc describe volumesnapshot mysnap

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   The following example displays details about the mysnap volume snapshot:

   volumesnapshot.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshot
   metadata:
     name: mysnap
   spec:
     source:
       persistentVolumeClaimName: myclaim
     volumeSnapshotClassName: csi-hostpath-snap
   status:
     boundVolumeSnapshotContentName: snapcontent-1af4989e-a365-4286-96f8-d5dcd65d78d6 

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     creationTime: "2020-01-29T12:24:30Z" 

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     readyToUse: true 

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     restoreSize: 500Mi

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   1

   The pointer to the actual storage content that was created by the controller.

   2

   The time when the snapshot was created. The snapshot contains the volume content that was available at this indicated time.

   3

   If the value is set to true, the snapshot can be used to restore as a new PVC.
   If the value is set to false, the snapshot was created. However, the storage back end needs to perform additional tasks to make the snapshot usable so that it can be restored as a new volume. For example, Amazon Elastic Block Store data might be moved to a different, less expensive location, which can take several minutes.

2. To verify that the volume snapshot was created, enter the following command:

   $ oc get volumesnapshotcontent

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   The pointer to the actual content is displayed. If the boundVolumeSnapshotContentName field is populated, a VolumeSnapshotContent object exists and the snapshot was created.

3. To verify that the snapshot is ready, confirm that the VolumeSnapshot object has readyToUse: true.

Procedure

1. Specify the deletion policy that you require in the VolumeSnapshotClass object, as shown in the following example:

   volumesnapshot.yaml

   apiVersion: snapshot.storage.k8s.io
   kind: VolumeSnapshotClass
   metadata:
     name: csi-hostpath-snap
   driver: hostpath.csi.k8s.io
   deletionPolicy: Delete 

   1

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   1

   When deleting the volume snapshot, if the Delete value is set, the underlying snapshot is deleted along with the VolumeSnapshotContent object. If the Retain value is set, both the underlying snapshot and VolumeSnapshotContent object remain.
   If the Retain value is set and the VolumeSnapshot object is deleted without deleting the corresponding VolumeSnapshotContent object, the content remains. The snapshot itself is also retained in the storage back end.

2. Delete the volume snapshot by entering the following command:

   $ oc delete volumesnapshot <volumesnapshot_name>

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   Example output

   volumesnapshot.snapshot.storage.k8s.io "mysnapshot" deleted

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3. If the deletion policy is set to Retain, delete the volume snapshot content by entering the following command:

   $ oc delete volumesnapshotcontent <volumesnapshotcontent_name>

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4. Optional: If the VolumeSnapshot object is not successfully deleted, enter the following command to remove any finalizers for the leftover resource so that the delete operation can continue:

   重要

   Only remove the finalizers if you are confident that there are no existing references from either persistent volume claims or volume snapshot contents to the VolumeSnapshot object. Even with the --force option, the delete operation does not delete snapshot objects until all finalizers are removed.

   $ oc patch -n $PROJECT volumesnapshot/$NAME --type=merge -p '{"metadata": {"finalizers":null}}'

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   Example output

   volumesnapshotclass.snapshot.storage.k8s.io "csi-ocs-rbd-snapclass" deleted

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   The finalizers are removed and the volume snapshot is deleted.

Procedure

1. Specify a VolumeSnapshot data source on a PVC as shown in the following:

   pvc-restore.yaml

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: myclaim-restore
   spec:
     storageClassName: csi-hostpath-sc
     dataSource:
       name: mysnap 

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       kind: VolumeSnapshot 

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       apiGroup: snapshot.storage.k8s.io 

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     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 1Gi

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   1

   Name of the VolumeSnapshot object representing the snapshot to use as source.

   2

   Must be set to the VolumeSnapshot value.

   3

   Must be set to the snapshot.storage.k8s.io value.

2. Create a PVC by entering the following command:

   $ oc create -f pvc-restore.yaml

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3. Verify that the restored PVC has been created by entering the following command:

   $ oc get pvc

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   Two different PVCs are displayed.