# Cloud Hypervisor — Lightweight Virtual Machine Monitor in Rust

> Cloud Hypervisor is a KVM-based virtual machine monitor written in Rust for modern cloud workloads. It provides a minimal attack surface, fast boot times, and support for CPU/memory/device hotplug with a focus on security and simplicity.

## Install

Save as a script file and run:

# Cloud Hypervisor — Lightweight Virtual Machine Monitor in Rust

## Quick Use
```bash
# Build from source
git clone https://github.com/cloud-hypervisor/cloud-hypervisor.git
cd cloud-hypervisor
cargo build --release

# Launch a VM
./target/release/cloud-hypervisor 
  --kernel vmlinux 
  --disk path=focal.raw 
  --cpus boot=2 --memory size=1024M 
  --net tap=tap0
```

## Introduction
Cloud Hypervisor is a virtual machine monitor (VMM) built on the rust-vmm project crates. It runs on Linux KVM and is designed for lightweight, secure VM execution in cloud infrastructure, offering a minimal codebase compared to QEMU while supporting essential cloud features like live migration and hotplug.

## What Cloud Hypervisor Does
- Boots Linux and Windows guest VMs on KVM with minimal overhead
- Supports CPU, memory, disk, and network device hotplug
- Provides live migration for moving running VMs between hosts
- Exposes a REST API for programmatic VM lifecycle management
- Runs with a minimal device model to reduce attack surface

## Architecture Overview
Cloud Hypervisor is built from modular rust-vmm crates: kvm-ioctls for KVM interaction, vm-memory for guest memory management, and virtio devices for I/O. The VMM process runs in user space, communicating with the kernel via KVM ioctls. A built-in HTTP API server allows external orchestrators to manage VM lifecycle.

## Self-Hosting & Configuration
- Requires Linux with KVM support (Intel VT-x or AMD-V)
- Build with cargo; the binary has no runtime dependencies beyond KVM
- Configure VMs via command-line flags or the REST API
- Use cloud-init or ignition for guest OS provisioning
- Deploy behind orchestrators like Kata Containers or custom cloud platforms

## Key Features
- Written in Rust for memory safety and reduced vulnerability surface
- Fast VM boot times (under 100ms for microVM workloads)
- CPU and memory hotplug for elastic scaling
- Live migration support for zero-downtime maintenance
- Virtio device model for efficient I/O

## Comparison with Similar Tools
- **QEMU** — full-featured with broad hardware emulation; Cloud Hypervisor is leaner and Rust-native
- **Firecracker** — microVM focus with minimal device model; Cloud Hypervisor adds hotplug and live migration
- **crosvm** — Chrome OS VM monitor; Cloud Hypervisor targets cloud infrastructure
- **NEMU** — Intel's stripped QEMU fork; Cloud Hypervisor is a ground-up Rust implementation

## FAQ
**Q: Can Cloud Hypervisor run Windows guests?**
A: Yes. It supports Windows guests with virtio drivers for disk and network.

**Q: How does it compare to Firecracker in performance?**
A: Boot times and overhead are similar. Cloud Hypervisor adds features like hotplug and live migration that Firecracker intentionally omits.

**Q: Does it support GPU passthrough?**
A: VFIO-based PCI device passthrough is supported, enabling GPU and other device passthrough.

**Q: Who uses Cloud Hypervisor?**
A: It is used in Microsoft Azure and other cloud platforms as a lightweight VMM for container and VM workloads.

## Sources
- https://github.com/cloud-hypervisor/cloud-hypervisor
- https://www.cloudhypervisor.org/

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Source: https://tokrepo.com/en/workflows/asset-d3285403
Author: Script Depot