Docker vs rkt: What are the differences?

Docker vs rkt: Key Differences

Docker and rkt are both container runtimes used to create, deploy, and manage containerized applications. However, there are several key differences that set these two tools apart:

1. Container Image Format: Docker uses its own container image format called Docker Image, which includes the application code along with its dependencies bundled together. On the other hand, rkt uses the App Container (ACI) format, which separates the application code and its dependencies into different layers. This allows for better security and easier management of container images in rkt.

2. Architecture and Design Philosophy: Docker is built around a client-server architecture, where the Docker daemon runs on the host system and manages the containers. In contrast, rkt follows a decentralized design philosophy, where each rkt instance is independent and self-contained. This makes rkt more lightweight and less reliant on a central daemon for operations.

3. Security Model: Docker has a relatively complex security model, where containers are run with elevated privileges by default. Although Docker has made significant improvements in security, the attack surface area is larger compared to rkt. On the other hand, rkt implements a simpler and more secure security model, by running containers with minimal privileges and using features like namespaces and seccomp for isolation.

4. Networking: Docker provides a built-in networking solution called Docker Networking, which allows containers to communicate with each other and the outside world. Docker Networking supports multiple networking drivers and provides features like port mapping and overlay networks. In comparison, rkt does not include a built-in networking solution. Instead, it relies on external tools like CNI (Container Network Interface) plugins for networking configurations.

5. Integration with Orchestration Tools: Docker has gained widespread popularity and has a strong ecosystem with excellent integration with orchestration tools like Kubernetes and Docker Swarm. Many containerized applications and tools have been developed specifically for the Docker ecosystem. While rkt has started gaining popularity, it has limited integration with orchestration tools and a smaller ecosystem compared to Docker.

6. Ease of Use and User Experience: Docker has invested heavily in providing a user-friendly and intuitive interface for building, deploying, and managing containers. The Docker CLI (Command Line Interface) is well-documented and widely adopted by developers and system administrators. On the other hand, rkt offers a more minimalistic and command-line focused user experience. Although rkt is straightforward to use, it may require a slightly steeper learning curve compared to Docker for beginners.

In summary, Docker and rkt differ in their container image format, architecture, security model, networking capabilities, integration with orchestration tools, and user experience. While Docker has a larger ecosystem and a more user-friendly interface, rkt offers better security and a decentralized design philosophy.