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Technical Overview

Kubernetes allows for extensions to its architecture in the form of custom resources: https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/. KubeVirt represents virtual machines as custom resources and manages changes to libvirt domains based on the state of those resources.

Project Components

• virt-api: This component provides a HTTP RESTful entrypoint to manage the virtual machines within the cluster.
• virt-controller: This component manages the state of each VMI within the Kubernetes cluster.
• virt-handler: This is a daemon that runs on each Kubernetes node. It is responsible for monitoring the state of VMIs according to Kubernetes and ensuring the corresponding libvirt domain is booted or halted accordingly.
• virt-launcher: This component is a place-holder, one per running VMI. It contains the running VMI and remains running as long as the VMI is defined.

Scripts

• cluster/kubectl.sh: This is a wrapper around Kubernetes' kubectl command so that it can be run directly from this checkout without logging into a node.
• cluster/virtctl.sh is a wrapper around virtctl. virtctl brings all virtual machine specific commands with it. It is supplement to kubectl. e.g. cluster/virtctl.sh console testvm.
• cluster/cli.sh helps you creating ephemeral kubernetes and openshift clusters for testing. This is helpful when direct management or access to cluster nodes is necessary. e.g. cluster/cli.sh ssh node01.

Makefile Commands

• make cluster-up: This will deploy a fresh environment, the contents of KUBE_PROVIDER will be used to determine which provider from the cluster directory will be deployed.
• make cluster-sync: After deploying a fresh environment, or after making changes to code in this tree, this command will sync the Pods and DaemonSets in the running KubeVirt environment with the state of this tree.
• make cluster-down: This will tear down a running KubeVirt enviornment.