Overview

The KubeVirt projects provides a set of [templates](https://docs.okd.io/latest/dev_guide/templates.html) to create VMs to handle common usage scenarios. These templates provide a combination of some key factors that could be further customized and processed to have a Virtual Machine object.

The key factors which define a template are - Workload Most Virtual Machine should be server or desktop to have maximum flexibility; the highperformance workload trades some of this flexibility to provide better performances. - Guest Operating System (OS) This allow to ensure that the emulated hardware is compatible with the guest OS. Furthermore, it allows to maximize the stability of the VM, and allows performance optimizations. - Size (flavor) Defines the amount of resources (CPU, memory) to allocate to the VM.

WebUI

Kubevirt project has [the official UI](https://github.com/kubevirt/web-ui). This UI supports creation VM using templates and templates features - flavors and workload profiles. To create VM from template, choose WorkLoads in the left panel >> press to the "Create Virtual Machine" blue button >> choose "Create from Wizzard". Next, you have to see "Create Virtual Machine" window

Common-templates

There is the [common-templates subproject](https://github.com/kubevirt/common-templates/) subproject. It provides official prepaired and useful templates. [Additional doc available](/workloads/templates/common-templates.md). You can also create templates by hand. You can find an example below, in the "Example template" section.

Example template

In order to create a virtual machine via OpenShift CLI, you need to provide a template defining the corresponding object and its metadata.

! Only VirtualMachine object is currently supported.

Here is an example template that defines an instance of the VirtualMachine object:

apiVersion: v1
kind: Template
metadata:
  annotations:
    description: OCP KubeVirt Fedora 27 VM template
    iconClass: icon-fedora
    tags: kubevirt,ocp,template,linux,virtualmachine
  labels:
    kubevirt.io/os: fedora27
    miq.github.io/kubevirt-is-vm-template: "true"
  name: vm-template-fedora
objects:
- apiVersion: kubevirt.io/v1alpha3
  kind: VirtualMachine
  metadata:
    labels:
      kubevirt-vm: vm-${NAME}
      kubevirt.io/os: fedora27
    name: ${NAME}
  spec:
    running: false
    template:
      metadata:
        creationTimestamp: null
        labels:
          kubevirt-vm: vm-${NAME}
          kubevirt.io/os: fedora27
      spec:
        domain:
          cpu:
            cores: ${{CPU_CORES}}
          devices:
            disks:
              - name: disk0
        volumes:
          - name: disk0
            persistentVolumeClaim:
              claimName: myroot
            - disk:
                bus: virtio
              name: registrydisk
              volumeName: registryvolume
            - disk:
                bus: virtio
              name: cloudinitdisk
              volumeName: cloudinitvolume
          machine:
            type: ""
          resources:
            requests:
              memory: ${MEMORY}
        terminationGracePeriodSeconds: 0
        volumes:
        - name: registryvolume
          registryDisk:
            image: registry:5000/kubevirt/fedora-cloud-registry-disk-demo:devel
        - cloudInitNoCloud:
            userData: |-
              #cloud-config
              password: fedora
              chpasswd: { expire: False }
          name: cloudinitvolume
  status: {}
parameters:
- description: Name for the new VM
  name: NAME
- description: Amount of memory
  name: MEMORY
  value: 4096Mi
- description: Amount of cores
  name: CPU_CORES
  value: "4"

Note that the template above defines free parameters \(NAME and CPU_CORES\) and the NAME parameter does not have specified default value.

An OpenShift template has to be converted into the JSON file via oc process command, that also allows you to set the template parameters.

A complete example can be found in the [KubeVirt repository](https://github.com/kubevirt/kubevirt/blob/master/cluster/examples/vm-template-fedora.yaml).

!> You need to be logged in by oc login command.

$ oc process -f cluster/vmi-template-fedora.yaml\
    -p NAME=testvmi \
    -p CPU_CORES=2
{
    "kind": "List",
    "apiVersion": "v1",
    "metadata": {},
    "items": [
        {

The JSON file is usually applied directly by piping the processed output to oc create command.

$ oc process -f cluster/examples/vm-template-fedora.yaml \
    -p NAME=testvm \
    -p CPU_CORES=2 \
    | oc create -f -
virtualmachine.kubevirt.io/testvm created

The command above results in creating a Kubernetes object according to the specification given by the template \(in this example it is an instance of the VirtualMachine object\).

It’s possible to get list of available parameters using the following command:

$ oc process -f cluster/examples/vmi-template-fedora.yaml --parameters
NAME                DESCRIPTION           GENERATOR           VALUE
NAME                Name for the new VM
MEMORY              Amount of memory                          4096Mi
CPU_CORES           Amount of cores                           4

Starting virtual machine from the created object

The created object is now a regular VirtualMachine object and from now it can be controlled by accessing Kubernetes API resources. The preferred way how to do this from within the OpenShift environment is to use oc patch command.

$ oc patch virtualmachine testvm --type merge -p '{"spec":{"running":true}}'
virtualmachine.kubevirt.io/testvm patched

Do not forget about virtctl tool. Using it in the real cases instead of using kubernetes API can be more convinient. Example:

$ virtctl start testvm
VM testvm was scheduled to start

As soon as VM starts, kubernates creates new type of object - VirtualMachineInstance. It has similar name to VirtualMachine. Example (not full output, it’s too big):

$ kubectl describe vm testvm
name:         testvm
Namespace:    myproject
Labels:       kubevirt-vm=vm-testvm
              kubevirt.io/os=fedora27
Annotations:  <none>
API Version:  kubevirt.io/v1alpha2
Kind:         VirtualMachine
.......

Cloud-init script and parameters

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, supports [cloud-init scripts](https://cloudinit.readthedocs.io/en/latest/)

Using registry images

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, supports creating VM’s disks from registry. RegistryDisk is a special type volume which supports downloading images from user-defined registry server.

Hack - use pre-downloaded image

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, can use pre-downloaded VM image, which can be a useful feature especially in the debug/development/testing cases. No special parameters required in the VM template or VM/VMI yaml config. The main idea is to create Kubernetes PersistentVolume and PersistentVolumeClaim corresponding to existing image in the file system. Example:

---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: mypv
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10G
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/sda1/images/testvm"
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: mypvc
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10G

Cloud-init script and parameters

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, supports [cloud-init scripts](https://cloudinit.readthedocs.io/en/latest/)

Using registry images

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, supports creating VM’s disks from registry. RegistryDisk is a special type volume which supports downloading images from user-defined registry server.

Hack - use pre-downloaded image

Kubevirt VM templates, just like kubevirt VM/VMI yaml configs, can use pre-downloaded VM image, which can be a useful feature especially in the debug/development/testing cases. No special parameters required in the VM template or VM/VMI yaml config. The main idea is to create Kubernetes PersistentVolume and PersistentVolumeClaim corresponding to existing image in the file system. Example:

---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: mypv
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10G
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/sda1/images/testvm"
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: mypvc
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10G

If you create this PV/PVC, then you have to put VM image in the file path

/mnt/sda1/images/testvm/disk.img

Avaible in the each OpenShift/Kubevirt compute nodes.

Additional information

You can follow [Virtual Machine Lifecycle Guide](/workloads/virtual-machines/life-cycle) for further reference.