This repository enables the use of a container runtime, containerd, to manage Firecracker microVMs. Like traditional containers, Firecracker microVMs offer fast start-up and shut-down and minimal overhead. Unlike traditional containers, however, they can provide an additional layer of isolation via the KVM hypervisor.
Potential use cases of Firecracker-based containers include:
- Sandbox a partially or fully untrusted third party container in its own microVM. This would reduce the likelihood of leaking secrets via the third party container, for example.
- Bin-pack disparate container workloads on the same host, while maintaining a high level of isolation between containers. Because the overhead of Firecracker is low, the achievable container density per host should be comparable to running containers using kernel-based container runtimes, without the isolation compromise of such solutions. Multi-tentant hosts would particularly benefit from this use case.
To maintain compatibility with the container ecosystem, where possible, we use container standards such as the OCI image format.
There are several components in this repository that enable containerd to use Firecracker microVMs to run containers:
- A control plugin managing the lifecycle of the runtime and implementing our control API to manage the lifecycle of microVMs. The control plugin is compiled in to the containerd binary since building a Go plugin out-of-tree is hard, which requires us to build a specialized containerd binary for firecracker-containerd.
- A runtime linking containerd (outside the microVM) to the Firecracker virtual machine monitor (VMM). The runtime is implemented as an out-of-process shim runtime communicating over ttrpc.
- An agent running inside the microVM, which invokes
runC via containerd's
containerd-shim-runc-v1to create standard Linux containers inside the microVM.
- A root file filesystem image builder that constructs a firecracker microVM root filesystem containing runc and the firecracker-containerd agent.
For more detailed information on the components and how they work, see architecture.md.
To support the widest variety of workloads, firecracker-containerd has to work with popular container orchestration frameworks such as Kubernetes and Amazon ECS, so we will work to ensure that the software is conformant or compatible where necessary. The project currently allows you to launch a few containers colocated in the same microVM, and we are exploring how to raise the number of containers. We recently added support for configuring networking at the microVM level with CNI plugins and provide a CNI plugin suitable for chaining called "tc-redirect-tap". Our short term roadmap includes constraining or "jailing" the Firecracker VMM process to improve the host security posture. Our longer-term roadmap includes polishing, packaging, and generally making firecracker-containerd easier to run as well as exploring CRI conformance and compatibility with Kubernetes.
Details of specific roadmap items are tracked in GitHub issues.
Please use GitHub issues to report problems, discuss roadmap items, or make feature requests.
If you've discovered an issue that may have security implications to users or developers of this software, please do not report it using GitHub issues, but instead follow Firecracker's security reporting guidelines.
Other discussion: For general discussion, please join us in the
channel on the Firecracker Slack.
This library is licensed under the Apache 2.0 License.