Fleet vs rkt: What are the differences?

Introduction

In the realm of containerization and orchestration tools, Fleet and rkt stand out as popular choices. However, they have distinct differences in their features and functionalities.

1. Container Format: Fleet primarily utilizes systemd-nspawn for containerization, providing a simple and efficient solution. In contrast, rkt focuses on compatibility with the App Container Specification (appc) and runs containers using its own runtime, enabling more flexibility in container management.

2. Configuration Management: Fleet uses systemd units and cloud-init for managing container configurations, allowing for seamless integration with existing systemd-based systems. On the other hand, rkt employs pod manifests and container definitions, emphasizing declarative configurations and enhanced control over the container environment.

3. Networking: Fleet relies on the CoreOS Flannel for networking, offering a straightforward overlay network solution for connecting containers. Meanwhile, rkt supports various networking plugins like CNI (Container Networking Interface), enabling users to choose from a range of networking solutions based on their specific requirements.

4. Security Model: Fleet focuses on managing units that run as system services, leveraging existing system security mechanisms for isolation. In contrast, rkt emphasizes security through features like using SELinux or AppArmor for container isolation and employing Image Signing to ensure the integrity and authenticity of container images.

5. Community Support: Fleet, developed by CoreOS, has garnered a strong community following within the CoreOS ecosystem, receiving updates and support from the CoreOS community. In comparison, rkt, initially developed by CoreOS and later donated to the CNCF, benefits from broader community contributions and a more diverse set of development resources.

6. Ecosystem Integration: Fleet is tightly integrated with CoreOS tools like etcd for distributed key-value store functionality, enhancing cluster coordination. Conversely, rkt offers compatibility with various container image formats, allowing for seamless integration with container registries and tools, thus providing greater flexibility in the container ecosystem.

In Summary, Fleet and rkt differ in container format, configuration management, networking, security model, community support, and ecosystem integration, catering to unique user preferences and requirements in container orchestration.