# KubeVirt — Run Virtual Machines on Kubernetes

> KubeVirt extends Kubernetes with VM-native workloads. It lets you declare, schedule and manage traditional virtual machines as first-class Kubernetes objects alongside containers, sharing the same networking and storage.

## Install

Save in your project root:

# KubeVirt — Virtual Machines on Kubernetes

## Quick Use
```bash
export VERSION=v1.3.0
kubectl apply -f https://github.com/kubevirt/kubevirt/releases/download/${VERSION}/kubevirt-operator.yaml
kubectl apply -f https://github.com/kubevirt/kubevirt/releases/download/${VERSION}/kubevirt-cr.yaml

# Create a VM
cat <<EOF | kubectl apply -f -
apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  name: demo
spec:
  running: true
  template:
    spec:
      domain:
        devices:
          disks: [{ name: disk0, disk: { bus: virtio } }]
        resources:
          requests: { memory: 512Mi }
      volumes:
        - name: disk0
          containerDisk: { image: quay.io/containerdisks/fedora:latest }
EOF

virtctl console demo
```

## Introduction
KubeVirt is a CNCF incubating project that turns every Kubernetes node into a hypervisor host via the Linux kernel KVM stack. Instead of running two platforms — one for containers, one for VMs — operators can manage stateful legacy workloads and modern cloud-native services using the same scheduling, networking and storage primitives.

## What KubeVirt Does
- Introduces `VirtualMachine`, `VirtualMachineInstance` and `VirtualMachineInstancePreset` CRDs
- Runs each VM inside a Pod via virt-launcher + libvirt + qemu-kvm
- Integrates with CNI for L2/L3 networking and with CSI for persistent storage
- Enables live migration, snapshots, cloning and HotPlug devices
- Ships companion tools (CDI, HCO, Forklift, MTV) for imports and data management

## Architecture Overview
A KubeVirt install includes an operator that manages several DaemonSets/Deployments: virt-api (admission and API), virt-controller (VM lifecycle), virt-handler (per-node agent) and virt-launcher (Pod wrapper for a VM). The handler programs the kernel through libvirt; the launcher runs a single qemu-kvm process per VM. CDI (Containerized Data Importer) manages disk images in PVCs, and the virtctl CLI covers console, VNC and live migration.

## Self-Hosting & Configuration
- Install via operator manifests or the Hyperconverged Cluster Operator (HCO) for batteries-included setups
- Node requirements: KVM-enabled CPU, nested virtualisation enabled if running in a cloud VM
- Use MultusCNI for VLAN-aware VM networking
- Use CDI to import qcow2/ISO images from HTTP, S3 or container registries
- Configure Storage Profiles to pick the right CSI snapshot/clone strategy per StorageClass

## Key Features
- First-class Kubernetes CRDs for VMs, with familiar kubectl workflows
- Live migration between nodes for maintenance and rebalancing
- HotPlug CPU, memory, disks and NICs
- Integrated with Multus, Calico, Cilium and SR-IOV for advanced networking
- Backed by a rich ecosystem (CDI, KubeSAN, Forklift) for VM migrations from oVirt/VMware

## Comparison with Similar Tools
- **Proxmox / vSphere** — dedicated hypervisors; KubeVirt unifies them with Kubernetes control
- **OpenStack Nova** — heavyweight VM platform; KubeVirt sits on top of Kubernetes primitives
- **Firecracker** — microVM focus for serverless; KubeVirt targets general-purpose VMs
- **kata-containers** — runs pods in VMs; KubeVirt exposes VMs themselves
- **virt-manager / libvirt alone** — great for single hosts, KubeVirt clusters them

## FAQ
**Q:** Can I run Windows workloads?
A: Yes. KubeVirt includes drivers and documentation for Windows guests, including VirtIO drivers and device passthrough.

**Q:** Does live migration work without shared storage?
A: Requires a ReadWriteMany volume or block-level replication for most storage classes; local storage can use storage-live-migration with CDI.

**Q:** How much overhead does virt-launcher add?
A: A few hundred MB per VM plus the qemu-kvm footprint. KVM itself runs near bare-metal speeds.

**Q:** Is it production ready?
A: Yes, it is used in production by Red Hat OpenShift Virtualization and many Kubernetes platforms.

## Sources
- https://github.com/kubevirt/kubevirt
- https://kubevirt.io

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Source: https://tokrepo.com/en/workflows/494fe800-38e7-11f1-9bc6-00163e2b0d79
Author: AI Open Source