Firecracker is an open-source virtualization technology designed for creating and managing secure, multi-tenant container and function-based services, particularly within serverless environments. Developed by Amazon Web Services, its primary purpose is to enable the efficient and secure execution of container and function workloads with minimal overhead. Firecracker achieves this by running workloads within lightweight virtual machines called microVMs. These microVMs combine the security and isolation benefits of hardware virtualization with the speed and flexibility of containers.
At its core, Firecracker utilizes a virtual machine monitor (VMM) that leverages the Linux Kernel Virtual Machine (KVM) to create and manage these microVMs. The technology is characterized by its minimalist design, intentionally excluding unnecessary devices and guest-facing functionalities. This design choice significantly reduces the memory footprint and the potential attack surface of each microVM, leading to improved security, faster startup times, and enhanced hardware utilization. Firecracker's architecture is centered around a single micro VMM process that exposes an API endpoint for configuration and management.
The API endpoint provides a comprehensive set of capabilities for managing microVMs. Users can configure the microVM by setting the number of vCPUs and memory size. They can also add and configure network interfaces, block devices (both read-write and read-only), and rate limiters for virtio devices. Furthermore, the API allows for the configuration of logging and metrics, the addition of vsock and entropy devices, and the management of memory hotplugging. Crucially, the API enables the starting of microVMs with specified kernel images, root file systems, and boot arguments. For x86_64 architectures, the API also supports stopping the microVM.
Firecracker offers several built-in capabilities to enhance security and performance. These include demand fault paging and CPU oversubscription, enabled by default, and advanced, thread-specific seccomp filters for improved security. A "Jailer" process is also included, which is designed for production scenarios. It applies a cgroup/namespace isolation barrier and then drops privileges to further enhance security.
Firecracker is actively used in production environments, including within AWS Lambda and AWS Fargate, demonstrating its reliability and scalability. The project is open-sourced under the Apache 2.0 license, encouraging community contributions and collaboration. The project has a well-defined release cycle, with new versions typically released every two to three months, and a detailed changelog to track changes. The project also provides comprehensive documentation, including a getting started guide, design documents, API specifications, and a security policy. The project also has a community Slack workspace and welcomes contributions.
The project is actively tested on a variety of platforms, including various AWS EC2 instance types with different host OS and guest kernel combinations. The project also has a security policy for reporting vulnerabilities. The project also has a FAQ document to address common questions.
