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Managing offline virtual machine snapshots

You can create, restore, and delete virtual machine (VM) snapshots for VMs that are powered off (offline). OpenShift Virtualization supports offline VM snapshots on:

  • Red Hat OpenShift Container Storage

  • Any other storage provider with the Container Storage Interface (CSI) driver that supports the Kubernetes Volume Snapshot API

About virtual machine snapshots

A snapshot represents the state and data of a virtual machine (VM) at a specific point in time. You can use a snapshot to restore an existing VM to a previous state (represented by the snapshot) for backup and disaster recovery or to rapidly roll back to a previous development version.

An offline VM snapshot is created from a VM that is powered off (Stopped state). The snapshot stores a copy of each Container Storage Interface (CSI) volume attached to the VM and a copy of the VM specification and metadata. Snapshots cannot be changed after creation.

With the offline VM snapshots feature, cluster administrators and application developers can:

  • Create a new snapshot

  • List all snapshots attached to a specific VM

  • Restore a VM from a snapshot

  • Delete an existing VM snapshot

Virtual machine snapshot controller and custom resource definitions (CRDs)

The VM snapshot feature introduces three new API objects defined as CRDs for managing snapshots:

  • VirtualMachineSnapshot: Represents a user request to create a snapshot. It contains information about the current state of the VM.

  • VirtualMachineSnapshotContent: Represents a provisioned resource on the cluster (a snapshot). It is created by the VM snapshot controller and contains references to all resources required to restore the VM.

  • VirtualMachineRestore: Represents a user request to restore a VM from a snapshot.

The VM snapshot controller binds a VirtualMachineSnapshotContent object with the VirtualMachineSnapshot object for which it was created, with a one-to-one mapping.

Creating an offline virtual machine snapshot in the CLI

You can create a virtual machine (VM) snapshot for an offline VM by creating a VirtualMachineSnapshot object.

Prerequisites

  • Ensure that the persistent volume claims (PVCs) are in a storage class that supports Container Storage Interface (CSI) volume snapshots.

  • Install the OpenShift CLI (oc).

  • Power down the VM for which you want to create a snapshot.

Procedure

  1. Create a YAML file to define a VirtualMachineSnapshot object that specifies the name of the new VirtualMachineSnapshot and the name of the source VM.

    For example:

    apiVersion: snapshot.kubevirt.io/v1alpha1
kind: VirtualMachineSnapshot
metadata:
  name: my-vmsnapshot (1)
spec:
  source:
    apiGroup: kubevirt.io
    kind: VirtualMachine
    name: my-vm (2)
    1 The name of the new VirtualMachineSnapshot object.
    2 The name of the source VM.

  2. Create the VirtualMachineSnapshot resource. The snapshot controller creates a VirtualMachineSnapshotContent object, binds it to the VirtualMachineSnapshot and updates the status and readyToUse fields of the VirtualMachineSnapshot object.

    $ oc create -f <my-vmsnapshot>.yaml
Verification

  1. Verify that the VirtualMachineSnapshot object is created and bound with VirtualMachineSnapshotContent. The readyToUse flag must be set to true.

    $ oc describe vmsnapshot <my-vmsnapshot>
    Example output
    apiVersion: snapshot.kubevirt.io/v1alpha1
kind: VirtualMachineSnapshot
metadata:
creationTimestamp: "2020-09-30T14:41:51Z"
finalizers:
- snapshot.kubevirt.io/vmsnapshot-protection
generation: 5
name: mysnap
namespace: default
resourceVersion: "3897"
selfLink: /apis/snapshot.kubevirt.io/v1alpha1/namespaces/default/virtualmachinesnapshots/my-vmsnapshot
uid: 28eedf08-5d6a-42c1-969c-2eda58e2a78d
spec:
source:
apiGroup: kubevirt.io
kind: VirtualMachine
name: my-vm
status:
conditions:
  - lastProbeTime: null
  lastTransitionTime: "2020-09-30T14:42:03Z"
  reason: Operation complete
  status: "False" (1)
  type: Progressing
  - lastProbeTime: null
  lastTransitionTime: "2020-09-30T14:42:03Z"
  reason: Operation complete
  status: "True" (2)
  type: Ready
creationTime: "2020-09-30T14:42:03Z"
readyToUse: true (3)
sourceUID: 355897f3-73a0-4ec4-83d3-3c2df9486f4f
virtualMachineSnapshotContentName: vmsnapshot-content-28eedf08-5d6a-42c1-969c-2eda58e2a78d (4)
    1 The status field of the Progressing condition specifies if the snapshot is still being created.
    2 The status field of the Ready condition specifies if the snapshot creation process is complete.
    3 Specifies if the snapshot is ready to be used.
    4 Specifies that the snapshot is bound to a VirtualMachineSnapshotContent object created by the snapshot controller.

  2. Check the spec:volumeBackups property of the VirtualMachineSnapshotContent resource to verify that the expected PVCs are included in the snapshot.

Restoring a virtual machine from a snapshot in the CLI

You can restore an existing virtual machine (VM) to a previous configuration by using a VM snapshot .

Prerequisites

  • Install the OpenShift CLI (oc).

  • Power down the VM you want to restore to a previous state.

Procedure

  1. Create a YAML file to define a VirtualMachineRestore object that specifies the name of the VM you want to restore and the name of the snapshot to be used as the source.

    For example:

    apiVersion: snapshot.kubevirt.io/v1alpha1
kind: VirtualMachineRestore
metadata:
  name: my-vmrestore (1)
spec:
  target:
    apiGroup: kubevirt.io
    kind: VirtualMachine
    name: my-vm (2)
  virtualMachineSnapshotName: my-vmsnapshot (3)
    1 The name of the new VirtualMachineRestore object.
    2 The name of the target VM you want to restore.
    3 The name of the VirtualMachineSnapshot object to be used as the source.

  2. Create the VirtualMachineRestore resource. The snapshot controller updates the status fields of the VirtualMachineRestore object and replaces the existing VM configuration with the snapshot content.

    $ oc create -f <my-vmrestore>.yaml
Verification

  • Verify that the VM is restored to the previous state represented by the snapshot. The complete flag must be set to true.

    $ oc get vmrestore <my-vmrestore>
    Example output
    apiVersion: snapshot.kubevirt.io/v1alpha1
kind: VirtualMachineRestore
metadata:
creationTimestamp: "2020-09-30T14:46:27Z"
generation: 5
name: my-vmrestore
namespace: default
ownerReferences:
- apiVersion: kubevirt.io/v1alpha3
  blockOwnerDeletion: true
  controller: true
  kind: VirtualMachine
  name: my-vm
  uid: 355897f3-73a0-4ec4-83d3-3c2df9486f4f
  resourceVersion: "5512"
  selfLink: /apis/snapshot.kubevirt.io/v1alpha1/namespaces/default/virtualmachinerestores/my-vmrestore
  uid: 71c679a8-136e-46b0-b9b5-f57175a6a041
  spec:
    target:
      apiGroup: kubevirt.io
      kind: VirtualMachine
      name: my-vm
  virtualMachineSnapshotName: my-vmsnapshot
  status:
  complete: true (1)
  conditions:
  - lastProbeTime: null
  lastTransitionTime: "2020-09-30T14:46:28Z"
  reason: Operation complete
  status: "False" (2)
  type: Progressing
  - lastProbeTime: null
  lastTransitionTime: "2020-09-30T14:46:28Z"
  reason: Operation complete
  status: "True" (3)
  type: Ready
  deletedDataVolumes:
  - test-dv1
  restoreTime: "2020-09-30T14:46:28Z"
  restores:
  - dataVolumeName: restore-71c679a8-136e-46b0-b9b5-f57175a6a041-datavolumedisk1
  persistentVolumeClaim: restore-71c679a8-136e-46b0-b9b5-f57175a6a041-datavolumedisk1
  volumeName: datavolumedisk1
  volumeSnapshotName: vmsnapshot-28eedf08-5d6a-42c1-969c-2eda58e2a78d-volume-datavolumedisk1
    1 Specifies if the process of restoring the VM to the state represented by the snapshot is complete.
    2 The status field of the Progressing condition specifies if the VM is still being restored.
    3 The status field of the Ready condition specifies if the VM restoration process is complete.

Deleting a virtual machine snapshot in the CLI

You can delete an existing virtual machine (VM) snapshot by deleting the appropriate VirtualMachineSnapshot object.

Prerequisites

  • Install the OpenShift CLI (oc).

Procedure

  • Delete the VirtualMachineSnapshot object. The snapshot controller deletes the VirtualMachineSnapshot along with the associated VirtualMachineSnapshotContent object.

    $ oc delete vmsnapshot <my-vmsnapshot>
Verification

  • Verify that the snapshot is deleted and no longer attached to this VM:

    $ oc get vmsnapshot

Additional resources