About FCOS

Containers allow workloads to be reproducibly deployed to production and automatically scaled to meet demand. The isolation provided by a container means that the host OS can be small. It only needs a Linux kernel, systemd, a container runtime, and a few additional services such as an SSH server.

While containers can be run on a full-sized server OS, an operating system built specifically for containers can provide functionality that a general-purpose OS cannot. Since the required software is minimal and uniform, the entire OS can be deployed as a unit with little customization. And, since containers are deployed across multiple nodes for redundancy, the OS can update itself automatically and then reboot without interrupting workloads.

Fedora CoreOS is built to be a secure and reliable host for your compute clusters. It’s designed specifically for running containerized workloads without regular maintenance, automatically updating itself with the latest OS improvements, bug fixes, and security updates. It provisions itself with Ignition, runs containers with Podman and Moby, and updates itself atomically and automatically with rpm-ostree.

Fedora CoreOS (FCOS) represents the next generation of single-purpose container operating system technology. FCOS is supported only as a component of OKD Latest for all OKD machines. FCOS is the only supported operating system for OKD control plane, or master, machines. While FCOS is the default operating system for all cluster machines, you can create compute machines, which are also known as worker machines, that use Fedora as their operating system.

Key Features of FCOS:

  • Based on Fedora
  • CRI-O container runtime
  • Set of container tools (Podman CLI, skopeo CLI, & crictl CLI)
  • rpm-ostree upgrades
  • Updated through MachineConfigOperator