CoreOS

CoreOS was an open source infrastructure software company whose products targeted the operation of containerized applications at scale. Its best-known project was Container Linux (originally CoreOS Linux), a lightweight Linux distribution first released on October 3, 2013 that provided only the minimal functionality needed to run applications inside software containers, along with built-in mechanisms for service discovery and configuration sharing. Container Linux shared a common software development kit foundation with Gentoo Linux, ChromeOS and ChromiumOS, used systemd as its init system, shipped no package manager (all payload applications ran in containers), and applied operating system updates via a dual-partition "FastPatch" scheme with a reboot manager called locksmith and an update-distribution mechanism derived from Google's open source Omaha project.

Beyond the operating system, CoreOS produced etcd, a distributed data store used by Kubernetes; rkt (initially released as Rocket) in December 2014 as an alternative container runtime implementing the app container (appc) specification and application container image (ACI) format that CoreOS created and positioned as input to the Open Container Initiative; CoreUpdate, a web dashboard and HTTP API for managing cluster-wide updates; CoreOS Tectonic, an enterprise-ready Kubernetes platform offering automated operations and portability across private and public clouds; and CoreOS Quay, a container registry offering. In November 2016 the company introduced Operators, a pattern for streamlining Kubernetes container management.

Following Red Hat's acquisition, the CoreOS name continues as a Red Hat-associated open source project building minimal container-optimized operating systems — Fedora CoreOS and RHEL CoreOS — using OCI containers as the transport and delivery mechanism for operating system content. Container Linux itself reached end-of-life, announced May 26, 2020, with Fedora CoreOS and RHEL CoreOS named as replacements (Flatcar Container Linux is also listed as a successor).

Founding story

Alex Polvi and Brandon Philips, friends since college, started CoreOS in 2013 through Y Combinator (Summer 2013 batch) after observing how difficult it was to keep systems current. Their core thesis was automated operations — automating updates and other tasks that burn out operations teams. Container Linux was developed primarily by Alex Polvi, Brandon Philips and Michael Marineau.

Business model

CoreOS developed open source infrastructure projects and monetized through commercial, enterprise-oriented products layered on top of them, including the Tectonic Kubernetes platform, the Quay container registry and the CoreUpdate management dashboard. The company described a strategy analogous to cloud providers: establish core platform capabilities and then build additional products that run on the platform.

Paid enterprise products and services around its open source stack (Tectonic Kubernetes platform, Quay registry, CoreUpdate), with the underlying components distributed as open source under the Apache License 2.0.

Traction

Y Combinator lists a team size of 150. etcd became the distributed data store for Kubernetes, and the company's technologies were described as award-winning and as enabling broad adoption of containerized applications. The GitHub organization hosts 274 repositories, with widely used projects such as Ignition (974 stars), coreos-assembler (392), Butane (332), coreos-installer (244) and bootupd (194).

Latest developments

Red Hat completed the absorption of CoreOS into its portfolio; the coreos.com domain now resolves to Red Hat OpenShift material and Red Hat maintains a page describing what CoreOS was. Container Linux reached end-of-life in 2020 (final release 2512.3.0 on May 22, 2020), and the CoreOS project continues under Red Hat as Fedora CoreOS and RHEL CoreOS, with repositories actively updated through 2026.