CoreOS vs RancherOS: What are the differences?

Introduction

CoreOS and RancherOS are two leading container-focused operating systems that have gained popularity among developers and DevOps professionals. While both OSes are designed for containerized applications, they have several key differences that set them apart. In this article, we will explore and highlight the main distinctions between CoreOS and RancherOS.

1. Minimalism and Containerization Approach: One of the primary differences between CoreOS and RancherOS is their approach to minimalism and containerization. CoreOS follows a minimalistic design philosophy, focusing on simplicity and security. It employs a lightweight Linux distribution and incorporates core technologies such as Docker for containerization and etcd for managing distributed systems. On the other hand, RancherOS takes a container-first approach, where the entire operating system is designed and composed as a collection of containers. This unique architecture offers granular control over the OS components and enables quick updates and easy rollback.

2. ISO Installer vs. Cloud-Focused Installation: CoreOS provides an ISO installer, allowing users to install the OS on physical servers, virtual machines, or even bare-metal environments. This flexibility makes it suitable for various deployment scenarios. In contrast, RancherOS focuses on cloud-based deployment models. It offers a cloud-config YAML file that allows users to specify their desired configurations and provisions the OS automatically during the boot process. This cloud-centric installation method simplifies the deployment process and aligns well with cloud-native architectures.

3. Container Engine Choice: CoreOS primarily utilizes Docker as the container engine, providing a mature and widely used technology for containerization. However, it also supports other container runtimes such as rkt. On the other hand, RancherOS uses its own container runtime called "rancher-containerd," which is a lightweight, fully compatible runtime derived from "containerd." This distinction in container engines provides flexibility in choosing the most suitable runtime for specific use cases.

4. System Services and Management: CoreOS employs a service manager called "systemd" that is known for its widespread adoption in various Linux distributions. It provides advanced service management capabilities such as dependency tracking, resource control, and systemd unit files. RancherOS, on the other hand, takes a different approach and uses its own built-in system services management tool. This tool provides a variety of system services such as console, network, SSH, and more, all running as containers. This containerized approach simplifies system administration and enables easy customization.

5. Update Strategies: CoreOS follows a rolling release model, where updates are continuously delivered to the OS without disrupting running applications. This approach ensures that the OS is always up to date with the latest security patches and bug fixes. RancherOS, on the other hand, adopts a more traditional approach with long-term support (LTS) releases. These LTS releases are versioned and provide a stable platform for production environments. RancherOS users can choose to update to new LTS releases manually based on their requirements.

6. Platform and Ecosystem Support: CoreOS has established itself as a popular choice and has a robust ecosystem with a wide range of integrations and tools available. It is widely supported by various container orchestration platforms like Kubernetes, Docker Swarm, and Apache Mesos. RancherOS, while gaining traction, has a relatively smaller ecosystem. It is primarily designed to work seamlessly with Rancher, a container management platform. This tight integration with Rancher offers additional management and orchestration features specifically tailored for RancherOS users.

In summary, CoreOS and RancherOS differ in their minimalism and containerization approach, installation methods, container engine choices, system service management, update strategies, and platform/ecosystem support. These distinctions enable users to choose the OS that best fits their specific container deployment and management needs.