VM Snapshot & Restore

A virtual machine (VM) snapshot captures the state and data of a virtual machine at the specific time when the snapshot was taken. It acts pretty much like the usual operating system snapshots. A VM snapshot is an exact copy of the VM and can be used for VM migration or for creating multiple instances of the same VM.

The snapshot.kubevirt.io API Group defines resources for snapshotting and restoring KubeVirt Virtual Machines.

Pre-requisites:

• CSI Persistent Storage with support for VolumeSnapshot API should be installed with CRDs required for VolumeSnapshot API such as VolumeSnapshot, VolumeSnapshotClass etc.

  • KubeVirt leverages the VolumeSnapshot functionality of Kubernetes CSI drivers for capturing persistent VirtualMachine state. It is required that VMs use DataVolumes or PersistentVolumeClaims backed by a StorageClass that supports VolumeSnapshots and a VolumeSnapshotClass is properly configured for that StorageClass.

• KubeVirt looks for Kubernetes Volume Snapshot-related APIs/resources in the v1 version. To make sure that KubeVirt's snapshot controller is able to snapshot the VirtualMachine and referenced volumes as expected, Kubernetes Volume Snapshot APIs must be served from v1 version.

• Snapshot/Restore support must be enabled in the feature gates to be supported. Platform9 KubeVirt has it enabled by default.

Snapshot a Virtual Machine

To snapshot a VirtualMachine named fedora-vm-1, apply the following yaml on the cluster:

apiVersion: snapshot.kubevirt.io/v1alpha1

kind: VirtualMachineSnapshot

metadata:

  name: snap-fedora-1

spec:

  source:

    apiGroup: kubevirt.io

    kind: VirtualMachine

    name: fedora-vm-1

Checking the snapshot progress:

$ kubectl get vmsnapshot -w

NAME            SOURCEKIND       SOURCENAME    PHASE   READYTOUSE   CREATIONTIME   ERROR

snap-fedora-1   VirtualMachine   fedora-vm-1

snap-fedora-1   VirtualMachine   fedora-vm-1   InProgress   false

snap-fedora-1   VirtualMachine   fedora-vm-1   InProgress   false

snap-fedora-1   VirtualMachine   fedora-vm-1   InProgress   false

snap-fedora-1   VirtualMachine   fedora-vm-1   Succeeded    true         0s

​

$ kubectl get volumesnapshot -w

NAME                                                            READYTOUSE   SOURCEPVC     SOURCESNAPSHOTCONTENT   RESTORESIZE   SNAPSHOTCLASS                SNAPSHOTCONTENT   CREATIONTIME   AGE

vmsnapshot-786c1511-9372-431b-b095-cb9bc494ed44-volume-rootfs                fedora-dv-1                                         csi-cephfsplugin-snapclass                                    0s

vmsnapshot-786c1511-9372-431b-b095-cb9bc494ed44-volume-rootfs                fedora-dv-1                                         csi-cephfsplugin-snapclass                                    0s

vmsnapshot-786c1511-9372-431b-b095-cb9bc494ed44-volume-rootfs   false        fedora-dv-1                                         csi-cephfsplugin-snapclass   snapcontent-65f9b955-1b69-4e04-bbc7-edbbd17e9fea                  0s

vmsnapshot-786c1511-9372-431b-b095-cb9bc494ed44-volume-rootfs   false        fedora-dv-1                                         csi-cephfsplugin-snapclass   snapcontent-65f9b955-1b69-4e04-bbc7-edbbd17e9fea                  0s

vmsnapshot-786c1511-9372-431b-b095-cb9bc494ed44-volume-rootfs   true         fedora-dv-1                           5Gi           csi-cephfsplugin-snapclass   snapcontent-65f9b955-1b69-4e04-bbc7-edbbd17e9fea   2s             2s

Restore a Virtual Machine

To restore the VM fedora-vm-1 from VirtualMachineSnapshot snap-fedora-1, Stop the VM, wait for it to be stopped and then apply the following yaml.

apiVersion: snapshot.kubevirt.io/v1alpha1

kind: VirtualMachineRestore

metadata:

  name: restore-fedora-1

spec:

  target:

    apiGroup: kubevirt.io

    kind: VirtualMachine

    name: fedora-vm-1

  virtualMachineSnapshotName: snap-fedora-1

Clean Snapshots

VirtualMachineSnapshots (and their corresponding VirtualMachineSnapshotContents) objects can be deleted when they are no longer required for the restoring.