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Virtink: Lightweight Virtualization Add-on for Kubernetes

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Virtink is a Kubernetes add-on for running Cloud Hypervisor virtual machines. By using Cloud Hypervisor as the underlying hypervisor, Virtink enables a lightweight and secure way to run fully virtualized workloads in a canonical Kubernetes cluster.

Compared to KubeVirt, Virtink:

  • does not use libvirt or QEMU. By leveraging Cloud Hypervisor, VMs has lower memory (≈30MB) footprints, higher performance and smaller attack surface.
  • does not require a long-running per-Pod launcher process, which further reduces runtime memory overhead (≈80MB).
  • is an especially good fit for running fully isolated Kubernetes clusters in an existing Kubernetes cluster. See our Cluster API provider and the knest tool for more details.

Virtink consists of 3 components:

  • virt-controller is the cluster-wide controller, responsible for creating Pods to run Cloud Hypervisor VMs.
  • virt-daemon is the per-Node daemon, responsible for further controlling Cloud Hypervisor VMs on Node bases.
  • virt-prerunner is the per-Pod pre-runner, responsible for preparing VM networks and building Cloud Hypervisor VM configuration.

NOTE: Virtink is still a work in progress, its API may change without prior notice.

Installation

Requirements

A few requirements need to be met before you can begin:

  • Kubernetes cluster v1.16 ~ v1.25
  • Kubernetes apiserver must have --allow-privileged=true in order to run Virtink's privileged DaemonSet. It's usually set by default.
  • cert-manager v1.0 ~ v1.8 installed in Kubernetes cluster. You can install it with kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.8.2/cert-manager.yaml.

Container Runtime Support

Virtink currently supports the following container runtimes:

  • Docker
  • containerd

Other container runtimes, which do not use virtualization features, should work too. However, they are not tested officially.

Hardware Virtualization Support

Hardware with virtualization support is required. You should check if /dev/kvm exists on each Kubernetes nodes.

Host Kernel Version

  • Minimum: v4.11
  • Recommended: v5.6 or above

Install Virtink

Install all Virtink components:

kubectl apply -f https://github.com/smartxworks/virtink/releases/download/v0.13.0/virtink.yaml

Once you have deployed Virtink, you can create your virtual machines.

Getting Started

Create a VM

Apply the following manifest to Kubernetes. Note it uses a container rootfs and as such doesn’t persist data.

cat <<EOF | kubectl apply -f -
apiVersion: virt.virtink.smartx.com/v1alpha1
kind: VirtualMachine
metadata:
  name: ubuntu-container-rootfs
spec:
  instance:
    memory:
      size: 1Gi
    kernel:
      image: smartxworks/virtink-kernel-5.15.12
      cmdline: "console=ttyS0 root=/dev/vda rw"
    disks:
      - name: ubuntu
      - name: cloud-init
    interfaces:
      - name: pod
  volumes:
    - name: ubuntu
      containerRootfs:
        image: smartxworks/virtink-container-rootfs-ubuntu
        size: 4Gi
    - name: cloud-init
      cloudInit:
        userData: |-
          #cloud-config
          password: password
          chpasswd: { expire: False }
          ssh_pwauth: True
  networks:
    - name: pod
      pod: {}
EOF

Like starting pods, it will take some time to pull the image and start running the VM. You can wait for the VM become running as follows:

kubectl wait vm ubuntu-container-rootfs --for jsonpath='{.status.phase}'=Running --timeout -1s

Access the VM (via SSH)

The easiest way to access the VM is via a SSH client inside the cluster. You can access the VM created above as follows:

export VM_NAME=ubuntu-container-rootfs
export VM_POD_NAME=$(kubectl get vm $VM_NAME -o jsonpath='{.status.vmPodName}')
export VM_IP=$(kubectl get pod $VM_POD_NAME -o jsonpath='{.status.podIP}')
kubectl run ssh-$VM_NAME --rm --image=alpine --restart=Never -it -- /bin/sh -c "apk add openssh-client && ssh ubuntu@$VM_IP"

Enter password when you are prompted to enter password, which is set by the cloud-init data in the VM manifest.

Manage the VM

Virtink supports various VM power actions. For example, you can power off the VM created above as follows:

export VM_NAME=ubuntu-container-rootfs
export POWER_ACTION=PowerOff
kubectl patch vm $VM_NAME --subresource=status --type=merge -p "{\"status\":{\"powerAction\":\"$POWER_ACTION\"}}"

You can also Shutdown, Reset, Reboot or Pause a running VM, or Resume a paused one. To start a powered-off VM, you can PowerOn it.

Demo Recording

asciicast

Roadmap

License

This project is distributed under the Apache License, Version 2.0.