phoenix-alpha / firecracker

Secure and fast microVMs for serverless computing.

Our mission is to enable secure, multi-tenant, minimal-overhead execution of container and function workloads.

Read more about the Firecracker Charter here.

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 Weaveworks Ignite.

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:

Instance	Host OS & Kernel	Guest Rootfs	Guest Kernel
m5d.metal	al2 linux_4.1	ubuntu 22.04	linux_4.14
m6i.metal	al2 linux_5.10		linux_5.10
m6a.metal	al2023 linux_6.1
m6g.metal
c7g.metal

Known issues and Limitations

• The SendCtrlAltDel API request is not supported for aarch64 enabled microVMs.
• If a CPU template is not used on x86_64, overwrites of MSR_IA32_TSX_CTRL MSR value will not be preserved after restoring from a snapshot.
• The pl031 RTC device on aarch64 does not support interrupts, so guest programs which use an RTC alarm (e.g. hwclock) will not work.
• Issues and limitations related to snapshots are described in a separate document.

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 [email protected].

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