Introduction to Korean
CoreOS is a Linux distribution designed from scratch to run large-scale container workloads. Its focus is on providing a minimum, safe and up-to-date operating system automatically, allowing DevOps teams to focus on plutôt applications than on infrastructure management. Born in 2013, CoreOS introduced concepts such as atomic updates through OSTree and a cluster manager called Fleet, laying the foundations for the massive adoption of orchestrators such as Kubernetes. Although the original project has evolved towards Fedora CoreOS, its legacy continues to influence the way in which modern container-based infrastructure is built and operated.
Architecture and main components
The core of CoreOS is composed of several components that work together to provide a robust container platform. These include:
- etcd: a distributed and highly available key-value store that stores the cluster configuration and serves as a basis for the detection of services.
- Fleet: the service initiator that programs and manages the execution of units in the cluster nodes, similar to an init distributed system.
- locksmith: a coordination mechanism that avoids simultaneous updates in multiple nodes, ensuring that only one machine is restarted at a time during automatic updates.
- rkt (pronounced rocket): the container engine native to CoreOS, designed with a focus on safety and possibility, although today many users prefer Docker or containerd.
These elements form an infrastructure layer that hinders hardware complexity and allows applications to be deployed consistently in any cluster node.
Automatic updates and OSTree
One of the most distinctive features of CoreOS is its OSTree-based atomic update model. Instead of updating individual packages, the system manages complete file trees as immutable versions. When a new version is published, it is downloaded into an alternative partition and, after passing health controls, activated by a reboot. This approach drastically reduces the risk of failure after an update and allows for rapid setbacks if any problem is detected.
Safety and reduced attack surface
CoreOS maintains a minimum attack surface by including only the essential components for running containers. The system comes with no traditional package managers, no default interactive shells and a limited set of tools. In addition, it benefits from automatic safety updates and a design that promotes the isolation of workloads through namespaces and cgroups, which makes it difficult to spread possible exploits.
Integration with Kubernetes and other orchestrators
Although CoreOS was able to operate independently with Fleet, its true strength was manifested by aligning with the Kubernetes ecosystem. Many cloud service providers offered optimized CoreOS images to run kubelet and the Kubernetes control plane, taking advantage of their automatic update capacity to keep the nodes always parked. The combination of a light and safe host with a powerful orchestrator allowed organizations to build fully automated and scalable CI / CD pipelines.
Cases of use and adoption in industry
Companies from various sectors have adopted CoreOS as the basis for their container platforms, especially those that require high availability and updates without significant inactivity times. SaaS suppliers, streaming platforms and financial companies have reported improvements in the consistency of their environments and a reduction in operational load thanks to automatic updates. Open source projects such as etcd and Prometheus have also benefited from the stability of a Korean-based host.
Future and evolution towards Fedora CoreOS
In 2020, the CoreOS project was officially integrated into the Fedora community giving rise to Fedora CoreOS, which combines the best of CoreOS Container Linux with the life cycle and the innovations of Fedora. This new distribution maintains the principles of atomic updates, minimum attack surface and container focus, while benefiting from greater hardware support and the wide range of Fedora packages. Thus, the legacy of CoreOS continues alive, adapting to the changing needs of modern container-based infrastructure.
