CoreOS

CoreOS, Inc. was a technology company founded in 2013 that developed container-focused Linux distributions and tooling for cloud-scale deployments. Its flagship offerings included CoreOS Linux (later marketed as Container Linux), a minimal, headless operating system designed for automatic updates and running containers; the container runtime rkt; the distributed key-value store etcd; and the fleet cluster management tool. The company also produced Tectonic, a packaged Kubernetes distribution that integrated CoreOS components for easier cluster deployment.

CoreOS Linux/Container Linux emphasized a container-first approach, automated updates with rollback, and a small, secure footprint. It used Ignition for initial provisioning and supported update channels to balance stability and rapid improvements. The design embodied the concept of immutable infrastructure and declarative configuration, aiming to reduce drift across large fleets of servers.

In addition to the OS, CoreOS offered tools to support clustering and orchestration. Tectonic provided a turnkey Kubernetes deployment, while etcd served as the distributed configuration and state store for clusters. Fleet offered a method to manage systemd units across multiple machines, contributing to orchestration at scale.

Red Hat announced its acquisition of CoreOS in early 2018, with the deal closing soon thereafter. Following the acquisition, CoreOS technology was integrated into Red Hat’s offerings, and CoreOS Linux/Container Linux was eventually retired in favor of Fedora CoreOS and Red Hat CoreOS (RHCOS) for OpenShift deployments. Fedora CoreOS, released as the community successor in 2020, continues the project’s container-optimized host OS approach, while RHCOS serves as the node operating system for OpenShift.

CoreOS’s work influenced the evolution of container-centric operating systems, Kubernetes packaging, and automated update mechanisms that have shaped subsequent cloud-native projects.