Firecracker

What is Firecracker?

Firecracker is an open source virtualization technology that is purpose-built
for creating and managing secure, multi-tenant container and function-based
services that provide serverless operational models. Firecracker runs workloads
in lightweight virtual machines, called microVMs, which combine the security and
isolation properties provided by hardware virtualization technology with the
speed and flexibility of containers.

Overview

The main component of Firecracker is a virtual machine monitor (VMM) that uses
the Linux Kernel Virtual Machine (KVM) to create and run microVMs. Firecracker
has a minimalist design. It excludes unnecessary devices and guest-facing
functionality to reduce the memory footprint and attack surface area of each
microVM. This improves security, decreases the startup time, and increases
hardware utilization. Firecracker has also been integrated in container
runtimes, for example
Kata Containers and
Flintlock.

Firecracker was developed at Amazon Web Services to accelerate the speed and
efficiency of services like AWS Lambda and
AWS Fargate. Firecracker is open sourced
under Apache version 2.0.

To read more about Firecracker, check out
firecracker-microvm.io.

Getting Started

To get started with Firecracker, download the latest
release binaries
or build it from source.

You can build Firecracker on any Unix/Linux system that has Docker running (we
use a development container) and bash installed, as follows:

git clone https://github.com/firecracker-microvm/firecracker
cd firecracker
tools/devtool build
toolchain="$(uname -m)-unknown-linux-musl"

The Firecracker binary will be placed at
build/cargo_target/${toolchain}/debug/firecracker. For more information on
building, testing, and running Firecracker, go to the
quickstart guide.

The overall security of Firecracker microVMs, including the ability to meet the
criteria for safe multi-tenant computing, depends on a well configured Linux
host operating system. A configuration that we believe meets this bar is
included in the production host setup document.

Contributing

Firecracker is already running production workloads within AWS, but it's still
Day 1 on the journey guided by our mission. There's a lot more to
build and we welcome all contributions.

To contribute to Firecracker, check out the development setup section in the
getting started guide and then the Firecracker
contribution guidelines.

Releases

New Firecracker versions are released via the GitHub repository
releases page,
typically every two or three months. A history of changes is recorded in our
changelog.

The Firecracker release policy is detailed here.

Design

Firecracker's overall architecture is described in
the design document.

Features & Capabilities

Firecracker consists of a single micro Virtual Machine Manager process that
exposes an API endpoint to the host once started. The API is
specified in OpenAPI format. Read
more about it in the API docs.

The API endpoint can be used to:

• Configure the microvm by:
  • Setting the number of vCPUs (the default is 1).
  • Setting the memory size (the default is 128 MiB).
  • Configuring a CPU template.
• Add one or more network interfaces to the microVM.
• Add one or more read-write or read-only disks to the microVM, each represented
  by a file-backed block device.
• Trigger a block device re-scan while the guest is running. This enables the
  guest OS to pick up size changes to the block device's backing file.
• Change the backing file for a block device, before or after the guest boots.
• Configure rate limiters for virtio devices which can limit the bandwidth,
  operations per second, or both.
• Configure the logging and metric system.
• [BETA] Configure the data tree of the guest-facing metadata service. The
  service is only available to the guest if this resource is configured.
• Add a vsock socket to the microVM.
• Add a entropy device to the microVM.
• Start the microVM using a given kernel image, root file system, and boot
  arguments.
• [x86_64 only] Stop the microVM.

Built-in Capabilities:

• Demand fault paging and CPU oversubscription enabled by default.
• Advanced, thread-specific seccomp filters for enhanced security.
• Jailer process for starting Firecracker in production
  scenarios; applies a cgroup/namespace isolation barrier and then drops
  privileges.

Tested platforms

We test all combinations of:

Known issues and Limitations

• The pl031 RTC device on aarch64 does not support interrupts, so guest
  programs which use an RTC alarm (e.g. hwclock) will not work.

Performance

Firecracker's performance characteristics are listed as part of the
specification documentation. All specifications are a part
of our commitment to supporting container and function workloads in serverless
operational models, and are therefore enforced via continuous integration
testing.

Policy for Security Disclosures

The security of Firecracker is our top priority. If you suspect you have
uncovered a vulnerability, contact us privately, as outlined in our
security policy document; we will immediately prioritize your
disclosure.

FAQ & Contact

Frequently asked questions are collected in our FAQ doc.

You can get in touch with the Firecracker community in the following ways:

• Security-related issues, see our security policy document.
• Chat with us on our
  Slack workspace
  Note: most of the maintainers are on a European time zone.
• Open a GitHub issue in this repository.
• Email the maintainers at
  firecracker-maintainers@amazon.com.

When communicating within the Firecracker community, please mind our
code of conduct.