This is the CoreOS Assembler (often abbreviated COSA) build environment. It is a collection of various tools used to build Fedora CoreOS style systems, including RHEL CoreOS. The goal is that everything needed to build and test the OS comes encapsulated in one (admittedly large) container.

A high level goal of this tool is to support two highly related use cases, and to keep them as similar as possible:

• Local development ("test a kernel change")
• Be a production build system orchestrated by an external tool (e.g. Jenkins)

See fedora-coreos-pipeline as an example pipeline.

The container itself is available on Quay.io at quay.io/coreos-assembler/coreos-assembler. It includes the following tools:

• cosa: entrypoint for the COSA container and dispatcher to other commands:
  • To learn how to use COSA, see the Building Fedora CoreOS guide and the Working with CoreOS Assembler guide.
  • To learn how to develop on COSA, see the CoreOS Assembler Design guide and the Working on CoreOS Assembler guide.
• kola: for launching instances and running tests on them
• kolet: an agent for kola that runs on instances
• ore: for interfacing with cloud providers
• plume: for releasing Fedora CoreOS and Fedora Cloud

See the Building Fedora CoreOS guide to learn how to build Fedora CoreOS with COSA.

For more information about building a custom OS derived or based on Fedora CoreOS, see Custom OS.