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Hypervisors

Introduction

Kata Containers supports multiple hypervisors. This document provides a very high level overview of the available hypervisors, giving suggestions as to which hypervisors you may wish to investigate further.

Note:

This document is not prescriptive or authoritative:

  • It is up to you to decide which hypervisors may be most appropriate for your use-case.
  • Refer to the official documentation for each hypervisor for further details.

Types

Hypervisor Written in Architectures Type
Cloud Hypervisor rust aarch64, x86_64 Type 2 (KVM)
Firecracker rust aarch64, x86_64 Type 2 (KVM)
QEMU C all Type 2 (KVM)
Dragonball rust aarch64, x86_64 Type 2 (KVM)
StratoVirt rust aarch64, x86_64 Type 2 (KVM)

Determine currently configured hypervisor

$ kata-runtime kata-env | awk -v RS= '/\[Hypervisor\]/' | grep Path

Choose a Hypervisor

The table below provides a brief summary of some of the differences between the hypervisors:

Hypervisor Summary Features Limitations Container Creation speed Memory density Use cases Comment
Cloud Hypervisor Low latency, small memory footprint, small attack surface Minimal excellent excellent High performance modern cloud workloads
Firecracker Very slimline Extremely minimal Doesn't support all device types excellent excellent Serverless / FaaS
QEMU Lots of features Lots good good Good option for most users
Dragonball Built-in VMM, low CPU and memory overhead Minimal excellent excellent Optimized for most container workloads out-of-the-box Kata Containers experience
StratoVirt Unified architecture supporting three scenarios: VM, container, and serverless Extremely minimal(MicroVM) to Lots(StandardVM) excellent excellent Common container workloads StandardVM type of StratoVirt for Kata is under development

For further details, see the Virtualization in Kata Containers document and the official documentation for each hypervisor.

Hypervisor configuration files

Since each hypervisor offers different features and options, Kata Containers provides a separate configuration file for each. The configuration files contain comments explaining which options are available, their default values and how each setting can be used.

Hypervisor Golang runtime config file golang runtime short name golang runtime default rust runtime config file rust runtime short name rust runtime default
Cloud Hypervisor configuration-clh.toml clh configuration-cloud-hypervisor.toml cloud-hypervisor
Firecracker configuration-fc.toml fc
QEMU configuration-qemu.toml qemu yes configuration-qemu.toml qemu
Dragonball configuration-dragonball.toml dragonball yes
StratoVirt configuration-stratovirt.toml stratovirt

Notes:

  • The short names specified are used by the kata-manager tool.
  • As shown by the default columns, each runtime type has its own default hypervisor.
  • The golang runtime is the current default runtime.
  • The rust runtime, also known as runtime-rs, is the newer runtime written in the rust language.
  • See the Configuration for further details.
  • The configuration file links in the table link to the "source" versions: these are not usable configuration files as they contain variables that need to be expanded:
    • The links are provided for reference only.
    • The final (installed) versions, where all variables have been expanded, are built from these source configuration files.
  • The pristine configuration files are usually installed in the /opt/kata/share/defaults/kata-containers/ or /usr/share/defaults/kata-containers/ directories.
  • Some hypervisors may have the same name for both golang and rust runtimes, but the file contents may differ.
  • If there is no configuration file listed for the golang or rust runtimes, this either means the hypervisor cannot be run with a particular runtime, or that a driver has not yet been made available for that runtime.

Switch configured hypervisor

To switch the configured hypervisor, you only need to run a single command. See the kata-manager documentation for further details.