How To Set Up Kubevirt For Kubernetes Based VM Management

In this article, you will learn how to set up Kubevirt for Kubernetes based VM management.

Kubevirt For VM Management

Kubevirt is an open-source project that makes it possible for virtual machines to be manageand isd by Kubernetes. This means that Kubevirt VMs will be able to run on Pods, alongside containers – allowing you to manage and operate all your infrastructure, whether it is VMs or containers, using the Kubernetes control plane.

This enables a variety of use cases. Certain applications can’t be containerized, like legacy monolithic applications. Others don’t benefit from the investment of containerization. And for many organizations, the journey to containerization is a long one. VMs will still need to be managed and operated alongside containers for a long time to come.

The Kubevirt project includes a large list of capabilities and the Kubernetes ecosystem has now evolved in a way that most essential VM capabilities can be put together to make VM lifecycle management easy. These include support for multiple network interfaces using Multus, live migration of VMs, high availability, and importing disks using CDI (for example, from VMware environments).

Read on to learn about how you can install and run kubevirt, create and manage VMs in a Kubernetes cluster, and see some popular VM lifecycle capabilities in action.

Prerequisites

A Kubernetes Cluster.

Privileged containers must be allowed

Apiserver flag: --allow-privileged=true

Supported container runtimes:

- docker
- crio

Quickstart

Run kubevirt/apply-kubevirt-no-hardware-support.sh or kubevirt/apply-kubevirt.sh as appropriate
Apply vm/containerdisk.yaml to create the 1vCPU/1Gi RAM VM as described below
Remember to edit the cloudInitNoCloud cloud-config with your own root password and SSH key

No hardware virtualization support?

Run these commands before installing KubeVirt:

kubectl create namespace kubevirt
kubectl create configmap -n kubevirt kubevirt-config --from-literal debug.useEmulation=true --from-literal feature-gates="LiveMigration"

Installation of Kubevirt for Kubernetes based VM management

Deploy the KubeVirt operator

kubectl apply -f https://github.com/kubevirt/kubevirt/releases/download/v0.25.0/kubevirt-operator.yaml

Create the KubeVirt CR

kubectl apply -f https://github.com/kubevirt/kubevirt/releases/download/v0.25.0/kubevirt-cr.yaml

Enable Live Migration

kubectl create configmap -n kubevirt kubevirt-config --from-literal feature-gates="LiveMigration"

Optional: Wait until all KubeVirt components come up

kubectl -n kubevirt wait kv kubevirt --for condition=Available --timeout=-1s

Optional: Install KubeVirt kubectl plugin

Install krew
kubectl krew install virt

Optional: Enable VNC proxy

kubectl apply -f kubevirt/vnc.yaml

CDI Installation

Deploy the CDI operator

kubectl apply -f https://github.com/kubevirt/containerized-data-importer/releases/download/v1.13.1/cdi-operator.yaml

Create the CDI CR

kubectl create -f https://github.com/kubevirt/containerized-data-importer/releases/download/v1.13.1/cdi-cr.yaml

Deploy a VM

This manifest will deploy a 1 vCPU, 1Gi RAM Ubuntu 16.04 VM

It will require ~1 CPU and ~1GB of RAM to be successfully scheduled on a node

This VM may be live migrated
The VM uses containerDisk storage, meaning it will not survive the destruction of its pod through any means

It uses the Docker scratch space on a Kubernetes node
It does not require any persistent storage support (i.e PVC)
Do not run any important workloads on the sample VM!

Replace $YOUR_KEY_HERE with an SSH public key, and $YOUR_PASSWORD_HERE with a root password (for serial console access)

apiVersion: kubevirt.io/v1alpha3
kind: VirtualMachine
metadata:
  name: test-vm
  namespace: default
spec:
  running: true
  template:
    metadata:
      labels:
        kubevirt.io/name: test-vm
    spec:
      domain:
        cpu:
          threads: 1
          cores: 1
          sockets: 1
        memory:
          guest: "1G"
        devices:
          autoattachPodInterface: true # true by default, explicitly setting for clarity
          disks:
          - name: bootdisk
            disk:
              bus: virtio
          - name: cloud-init
            disk:
              bus: virtio
          interfaces:
          - name: default
            masquerade: {}
      terminationGracePeriodSeconds: 0
      networks:
      - name: default
        pod: {}
      volumes:
      - name: bootdisk
        containerDisk:
          image: camelcasenotation/ubuntu1604-containerdisk:latest
      - name: cloud-init
        cloudInitNoCloud:
          userData: |-
            #cloud-config
            users:
              - name: root
                ssh-authorized-keys:
                  - $YOUR_KEY_HERE
            ssh_pwauth: True
            password: $YOUR_PASSWORD_HERE
            chpasswd:
              expire: False
              list: |-
                 root:$YOUR_PASSWORD_HERE

Access the VM

Now that we’ve set up Kubevirt for Kubernetes based VM management, let’s access our VM.

Be careful when exposing VMs externally with a NodePort service and a weak password

Serial console is only possible with kubectl virt plugin

SSH in as root user

With virt:

SSH access:

kubectl virt expose vmi test-vm --port=22 --name=test-vm-ssh --type=NodePort

Serial console:

virtctl console test-vm

Without virt:

apiVersion: v1
kind: Service
metadata:
  name: test-vm-ssh
  namespace: default
spec:
  ports:
  - name: test-vm-ssh
    protocol: TCP
    port: 22
    targetPort: 22
  selector:
    kubevirt.io/name: test-vm
  type: NodePort

With VNC:

If VNC is not enabled yet

kubectl apply -f kubevirt/vnc/vnc.yaml

Look up VNC service nodeport
Access VMs at

http://NODE_IP:NODEPORT/?namespace=VM_NAMESPACE

Only VMs under the namespace VM_NAMESPACE will be shown. Choose the namespace that your desired VM is under.

Test CDI

Make sure to fill out all the variables in the DataVolume/VM manifests to suit your environment before applying
Try to create a DataVolume

kubectl apply -f datavolume/datavolume-cirros.yaml
kubectl apply -f datavolume/datavolume-ubuntu.yaml
kubectl get datavolumes

Use a DataVolume on-the-fly in a VM manifest

kubectl apply -f vm/CDI-PVC.yaml

Uninstall

export RELEASE=v0.25.0
kubectl delete -n kubevirt kubevirt kubevirt --wait=true # --wait=true should anyway be default
kubectl delete apiservices v1alpha3.subresources.kubevirt.io # this needs to be deleted to avoid stuck terminating namespaces
kubectl delete mutatingwebhookconfigurations virt-api-mutator # not blocking but would be left over
kubectl delete validatingwebhookconfigurations virt-api-validator # not blocking but would be left over
kubectl delete -f https://github.com/kubevirt/kubevirt/releases/download/${RELEASE}/kubevirt-operator.yaml --wait=false

If these commands get stuck, delete the finalizer and rerun the uninstallation commands

Delete Finalizer

kubectl -n kubevirt patch kv kubevirt --type=json -p '[{ "op": "remove", "path": "/metadata/finalizers" }]'

Troubleshooting

Ensure that Kubernetes has enough spare CPU/RAM to deploy your requested VM

Ensure that hardware virtualization is supported and available, or that the software virtualization flag is present in the ConfigMap
Changing the flag requires a deployment restart

Ensure that the service selector correctly targets the VM pod

Check that the Docker MTU and CNI plugin MTU are appropriate for your network

Use kubectl virt console $VM_NAME_HERE to ensure that VM has started

References

Next Steps

In this blog, we walked through a tutorial on how to set up Kubevirt for Kubernetes based VM management. We hope you found this blog informative and engaging. For more reads like this one, visit our blog page or subscribe for up-to-date news, projects, and related content in real-time.

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Author
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Peter Fray

Chief Technologist at Platform9 Systems

With a unique blend of technical experience - from IaaS, networking, Kubernetes, databases, and more - he helps large enterprises successfully adopt cloud, containers and modern technologies to accelerate application delivery and improve data center utilization.