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.. _live-migration-support-for-vms-bea635bacc50:

==============================
Live Migration Support for VMs
==============================

Live migration is a process during which a running |VMI| moves to another
compute node while the guest workload continues to run and remain accessible.


Enable the Live Migration Support
---------------------------------

Live migration is enabled by default in recent versions of KubeVirt. Versions
prior to v0.56 must be enabled in the feature gates. The feature gates field in
the KubeVirt Custom Resource must be expanded by adding the live migration to
it.

Limitation for live migrations:

-   |VMs| using a |PVC| must have a shared |RWX| access mode to be live
    migrated.

-   Live migration is not allowed with a pod network binding of bridge
    interface type ().

-   Live migration requires ports 49152, 49153 to be available in the
    ``virt-launcher`` pod. If these ports are explicitly specified in
    a masquarade interface, live migration will not function.


Initiate Live Migration
-----------------------

Live migration is initiated by posting a |VMIM| object to the cluster. The
example below starts a migration process for a virtual machine instance
``vmi-fedora``.

.. code-block:: yaml

    cat <<EOF> migration.yaml
    apiVersion: kubevirt.io/v1
    kind: VirtualMachineInstanceMigration
    metadata:
      name: migration-job
    spec:
      vmiName: vmi-fedora
    EOF

    kubectl apply -f migration.yaml 

Use virtctl to initiate Live Migration
--------------------------------------

Live migration can also be initiated using ``virtctl``.

.. code-block:: none

    virtctl migrate vmi-fedora


Live Migration for SRIOV based VMs
----------------------------------

It is possible to live migrate |SRIOV| based |VMs|, but there are some
limitations:

-   Specify the MAC address statically and on host the name of the |SRIOV|
    interface should be same on source and target host.

-   Specify the Static IP address.

Below is an example manifest for |SRIOV| |VM| using a static MAC address:

.. code-block:: none

    apiVersion: kubevirt.io/v1
    kind: VirtualMachine
    metadata:
      labels:
        special: vmi-sriov-network
      name: vmi-sriov-test-vm
    spec:
      running: true
      template:
        metadata:
          labels:
            kubevirt.io/size: small
            kubevirt.io/domain: fedora
        spec:
          domain:
            cpu:
              cores: 4
            devices:
              disks:
              - name: containerdisk
                disk:
                  bus: virtio
              - name: cloudinitdisk
                disk:
                  bus: virtio
              interfaces:
              - macAddress: "02:00:00:00:00:01"
                name: sriov-net1
                sriov: {}
              rng: {}
            resources:
              requests:
                memory: 1024M
          networks:
          - multus:
              networkName: sriov-net1
            name: sriov-net1
          volumes:
          - containerDisk:
              image: docker.io/kubevirt/fedora-cloud-container-disk-demo:devel
            name: containerdisk
          - cloudInitNoCloud:
              networkData: |
                ethernets:
                  sriov-net1:
                    addresses:
                    - 10.10.10.12/24
                    gateway: 10.10.10.1
                    match:
                      macAddress: "02:00:00:00:00:01"
                    nameservers:
                      addresses:
                      - 10.96.0.10
                      search:
                      - default.svc.cluster.local
                      - svc.cluster.local
                      - cluster.local
                    set-name: sriov-link-enabled
                version: 2
              userData: |-
                #!/bin/bash
                echo "fedora" |passwd fedora --stdin
            name: cloudinitdisk


Below is an example manifest to initiate the live migration:

.. code-block:: none

    apiVersion: kubevirt.io/v1
    kind: VirtualMachineInstanceMigration
    metadata:
      name: migration-job-1
    spec:
      vmiName: vmi-sriov-test-vm