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Backing Up and Restoring KubeVirt resources

Introduction

This document is intended for developers building backup/disaster recovery solutions for KubeVirt.

Such solutions typically perform the following high level operations.

Backup

  1. Build dependency graph for all required Kubernetes resources
  2. Quiesce (freeze) applications
  3. Snapshot PersistentVolumeClaim data
  4. Unquiesce (thaw) applications
  5. Copy all necessary Kubernetes resource definitions to a shared storage location
  6. (optional) Export snapshotted PVC data to a shared storage location

Steps 3, 5, and 6 are beyond the scope of this document.

Restore

  1. Populate PersistentVolumeClaims with snapshot data
  2. Sanitize and apply all relevant Kubernetes resource definitions

Step 1 is beyond the scope of this document.

Existing KubeVirt Backup Solutions

Velero Plugin

Velero is a popular tool for backing up/migrating Kubernetes clusters. The KubeVirt team actively maintains a plugin for use with Velero. The plugin implements much of the logic described in this document.

VirtualMachineSnapshot + VirtualMachineExport API

The VirtualMachineSnapshot API provides an easy way for KubeVirt users to backup VirtualMachines within a cluster. On its own, it is not suitable for offsite backup or disaster recovery. But combined with the VirtualMachineExport API, VirtualMachine volumes may be made available for copy to remote locations.

Building the KubeVirt Object Graph

Object Graph Example

In this section, KubeVirt resources and their relationships will be explored by showing how yaml snippets map to nodes in an object graph.

Nodes in the object graph are represented by the following tuple:

(APIGroup, Kind, namespace, name)

VirtualMachine Object Graph

apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  name: vm1
  namespace: ns1
...
  • ("kubevirt.io", "VirtualMachine", "ns1", "vm1")

spec.instancetype

...
spec:
  instancetype:
    kind: VirtualMachineInstancetype
    name: small
    revisionName: vm1-small-XXXXX-1
...
  • ("instancetype.kubevirt.io", "VirtualMachineInstancetype", "ns1", "small")
  • ("apps", "controllerrevisions", "ns1", "vm1-small-XXXXX-1")

spec.preference

...
spec:
  preference:
    kind: VirtualMachinePreference
    name: windows
    revisionName: vm1-windows-XXXXX-1
...
  • ("instancetype.kubevirt.io", "VirtualMachinePreference", "ns1", "windows")
  • ("apps", "controllerrevisions", "ns1", "vm1-windows-XXXXX-1")

spec.template

See VirtualMachineInstance

VirtualMachineInstance Object Graph

apiVersion: kubevirt.io/v1
kind: VirtualMachineInstance
metadata:
  name: vmi1
  namespace: ns1
...
  • ("kubevirt.io", "VirtualMachineInstance", "ns1", "vmi1")
  • ("", "Pod", "ns1", "virt-launcher-vmi1-XXXXX") *

* Each VirtualMachineInstance has a corresponding uniquely named Pod. The backup process can look up the name of this pod by using the kubevirt.io/created-by=<UID of VirtualMachineInstance> label selector.

spec.volumes[*].persistentVolumeClaim

...
spec:
  volumes:
  - name: v1
    persistentVolumeClaim:
      claimName: pvc1
...
  • ("", "PersistentVolumeClaim", "ns1", "pvc1")
  • ("cdi.kubevirt.io", "DataVolume", "ns1", "pvc1")

spec.volumes[*].dataVolume

...
spec:
  volumes:
  - name: v1
    dataVolume:
      name: dv1
...
  • ("", "PersistentVolumeClaim", "ns1", "dv1")
  • ("cdi.kubevirt.io", "DataVolume", "ns1", "dv1")

spec.volumes[*].configMap

...
spec:
  volumes:
  - name: v1
    configMap:
      name: cm1
...
  • ("", "ConfigMap", "ns1", "cm1")

spec.volumes[*].secret

...
spec:
  volumes:
  - name: v1
    secret:
      secretName: s1
...
  • ("", "Secret", "ns1", "s1")

spec.volumes[*].serviceAccount

...
spec:
  volumes:
  - name: v1
    serviceAccount:
      serviceAccountName: sa1
...
  • ("", "ServiceAccount", "ns1", "sa1")

spec.volumes[*].memoryDump

...
spec:
  volumes:
  - name: v1
    memoryDump:
      claimName: pvc1
...
  • ("", "PersistentVolumeClaim", "ns1", "pvc1")

spec.accessCredentials[*].sshPublicKey

...
spec:
  accessCredentials:
  - sshPublicKey:
      source:
        secret:
          secretName: my-pub-key
...
  • ("", "Secret", "ns1", "my-pub-key")

spec.accessCredentials[*].userPassword

...
spec:
  accessCredentials:
  - userPassword:
      source:
        secret:
          secretName: my-user-password
...
  • ("", "Secret", "ns1", "my-user-password")

VirtualMachineInstanceReplicaSet Object Graph

apiVersion: kubevirt.io/v1
kind: VirtualMachineInstanceReplicaSet
metadata:
  name: vmirs1
  namespace: ns1
...
  • ("kubevirt.io", "VirtualMachineInstanceReplicaSet", "ns1", "vmirs1")
  • ("kubevirt.io", "VirtualMachineInstance", "ns1", "vmirs1XXXX1") *
  • ("kubevirt.io", "VirtualMachineInstance", "ns1", "vmirs1XXXX2") *

* there are usually multiple VirtualMachineInstances corresponding to a VirtualMachineInstanceReplicaSet. The backup process can look up the name of this pod by using the kubevirt.io/vmReplicaSet=<name of VirtualMachineInstanceReplicaSet> label selector.

spec.template

See VirtualMachineInstance

Backup Actions

Guest filesystem freeze/thaw hooks

See this guide for how to execute the freeze/thaw hooks for each VirtualMachineInstance encountered in the object graph.

Restore Actions

VirtualMachine Restore

If restoring to a different cluster, and mac address or bios serial number are explicitly set, you should make sure there will be no collisions. These values are set in:

/spec/template/spec/domain/devices/interfaces/<index>/macAddress
/spec/template/spec/domain/firmware/serial

VirtualMachineInstance Restore

If a VirtualMachineInstance is owned by a VirtualMachine, it should not be restored. The KubeVirt controller will recreate the resource based on the VirtualMachine definition. Otherwise, VirtualMachineInstance definitions may be backed up/restored with the same precautions as VirtualMachine for mac address/bios.

/spec/domain/devices/interfaces/<index>/macAddress
/spec/domain/firmware/serial

virt-launcher Pod Restore

A Pod with “virt-launcher-” prefix that is *owned by a VirtualMachineInstance should not be restored.

DataVolume Restore

DataVolumes in Succeeded phase (status.phase) should have the following annotation added at restore time. Otherwise, the associated PersistentVolumeClaim may get corrupted. DataVolumes in any phase other than Succeeded do not need to be annotated.

cdi.kubevirt.io/storage.prePopulated: <datavolume name>

PersistentVolumeClaim Restore

PersistentVolumeClaims owned by DataVolumes must have the following annotation added at backup/restore time.

cdi.kubevirt.io/storage.populatedFor: <datavolume name>

Validate backup partner compatibility

In this section, we will describe the different scenarios a backup partner should test in order to assess its compatibility with Kubevirt.

Prerequisites

Cluster with the backup software and storage existing and Kubevirt + CDI installed.

To validate there are two options:

Automatically

We have made if possible for our partners to test their compatibility automatically by filling out an example template with a predefined API with their solution implementation of backup and restore. By doing that and defining some env variables you can ran a basic set of tests to determine the compatibility of the backup restore solution with kubevirt. Please refer to partner-compatibility-testing for more information.

Manually

As an alternative you can run yourselves the following scenarios with this given manifests: All the manifests are at: https://github.com/kubevirt/kubevirt-velero-plugin/tree/main/tests/manifests You will need to replace manually the storageClassName in each yaml with the storageclass you have in your cluster $kubectl get storageclass or you can use the following command instead of each apply in the tests descriptions: $cat <YAML_PATH> | sed 's/{{KVP_STORAGE_CLASS}}/<DESIRED_STORAGE_CLASS>/g' | kubectl create -f -n <NAMESPACE> -

Stopped VM with DataVolume and DataVolumeTemplate

Create namespace $kubectl create ns <NAMESPACE>

Apply blank datavolume and wait for it to be Succeeded: $kubectl apply -f -n <NAMESPACE> blank_datavolume.yaml

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_with_dv_and_dvtemplate.yaml

Write some data. Example: Access to the VM console $virtctl console test-vm-with-dv-and-dvtemplate In the console $echo "testing" > test.txt

Stop VM and wait for it to be Stopped $virtctl stop test-vm-with-dv-and-dvtemplate

Create backup for the namespace, wait for it to complete successfully.

Delete VM and Datavolume $kubectl delete -n <NAMESPACE> vm test-vm-with-dv-and-dvtemplate $kubectl delete -n <NAMESPACE> datavolume test-dv

Create restore from the backup and wait for completion.

Check DV reaches succeeded state right away.

Check VM is in stopped state.

Start VM and wait for it to be Running. Verify data exists.

VM running with standalone PVC

Create namespace $kubectl create ns <NAMESPACE>

Create ImportVolumeSource $kubectl apply -f -n <NAMESPACE> volume_import_source.yaml

Create PVC populated by the ImportVolumeSource $kubectl apply -f -n <NAMESPACE> import_populator_pvc.yaml

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_with_pvc.yaml

Write some data. Example: Access to the VM console $virtctl console test-vm-with-pvc In the console $echo "testing" > test.txt

Create backup for the namespace, wait for it to complete successfully.

Delete the Namespace

Create restore from the backup and wait for completion.

Check PVC exists and Bound

Check VM exists and running. Verify data exists.

VM with hotplug

Create namespace $kubectl create ns <NAMESPACE>

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_for_hotplug.yaml

Apply DV manifest and wait for it to be succeeded: $kubectl apply -f -n <NAMESPACE> blank_datavolume.yaml

Dynamically attach a volume to the running VM. $virtctl addvolume test-vm-for-hotplug --volume-name=test-dv Wait to see the attached volume in the VMI volumes and disks lists(vmi.Spec.Volumes, vmi.Spec.Domain.Devices.Disks)

Create backup for the namespace, wait for it to complete successfully.

Delete namespace

Create restore from the backup and wait for completion.

Check DV test-dv succeeded state right away.

Check VM reaches Running state and that the attached volume is in the VMI volumes and disks lists(vmi.Spec.Volumes, vmi.Spec.Domain.Devices.Disks)

VM stopped with ConfigMap, Secret and DVTemplate

Create namespace $kubectl create ns <NAMESPACE>

Apply ConfigMap $kubectl apply -f -n <NAMESPACE> configmap.yaml

Apply Secret $kubectl apply -f -n <NAMESPACE> secret.yaml

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_with_different_volume_types.yaml

Stop VM and wait for it to be Stopped

Create backup for the namespace, wait for it to complete successfully.

Delete namespace

Create restore from the backup and wait for completion.

Check DV reaches succeeded state right away.

Check ConfigMap and Secret exists

Check VM is in stopped state.

Start VM and wait for it to be Running.

VM running with AccessCredential and DVTemplate

Create namespace $kubectl create ns <NAMESPACE>

Apply AccessCredential $kubectl apply -f -n <NAMESPACE> accessCredentialsSecret.yaml

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_with_access_credentials.yaml

Create backup for the namespace, wait for it to complete successfully.

Delete namespace

Create restore from the backup and wait for completion.

Check DV reaches succeeded state right away.

Check AccessCredential exists

Check VM is Running.

VM with instancetype and preference

Create namespace $kubectl create ns <NAMESPACE>

Apply Instancetype $kubectl apply -f -n <NAMESPACE> instancetype.yaml

Apply Preference $kubectl apply -f -n <NAMESPACE> preference.yaml

Apply VM yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vm_with_instancetype_and_preference.yaml Check revision names updated in VM spec (vm.Spec.Instancetype.RevisionName, vm.Spec.Preference.RevisionName)

Create backup for the namespace, wait for it to complete successfully.

Delete namespace

Create restore from the backup and wait for completion.

Check VM reaches Running state

VMI with a standalone DV

Create namespace $kubectl create ns <NAMESPACE>

Apply DV yaml and wait for it to reach Succeeded state $kubectl apply -f -n <NAMESPACE> dv-with-guest-agent-image.yaml

Apply VMI yaml and wait for it to be Running: $kubectl apply -f -n <NAMESPACE> vmi_with_dv.yaml Make sure you see in the VMI conditions AgentConnected

Create backup for the namespace, wait for it to complete successfully.

Delete namespace

Create restore from the backup and wait for completion.

Check DV reaches succeeded state right away.

Check VMI reaches Running state.