development-scos.md

Building and developing CentOS Stream CoreOS

Background

CentOS Stream CoreOS (SCOS) is a derivative of both CentOS Stream and Fedora CoreOS (FCOS). The tool to build both SCOS and FCOS is coreos-assembler. The process detailled here is thus very similar to the one described in Building Fedora CoreOS.

Build process

• Make sure you're meeting the prerequisites.

• Setup a cosa alias, following the upstream documentation.

• Always make sure that you have the latest version of the COSA container:

  $ podman pull quay.io/coreos-assembler/coreos-assembler
  

• Create and use a dedicated directory:

  $ mkdir scos
  $ cd scos
  

• Clone the config repo (openshift/os):

  $ cosa init --variant scos https://github.com/openshift/os.git
  

• Temporary workaround until we have full repos for SCOS: Add the internal rhel-9-server-ose repo definition from RHCOS to rhcos9.repo:

  [rhel-9-server-ose]
  enabled=1
  gpgcheck=0
  baseurl=http://...
  

• Fetch packages and build SCOS ostree container and QEMU image:

  $ cosa fetch
  $ cosa build
  

Building SCOS images for other platforms than QEMU

• You can build images for platforms that are supported in COSA using the buildextend commands:

  $ cosa buildextend-aws
  $ cosa buildextend-openstack
  

Running SCOS locally for testing

• You may then run an ephemeral virtual machine using QEMU with:

  $ cosa run
  

Testing SCOS with kola

• You may then run tests on the image built with kola:

  # Run basic QEMU scenarios
  $ cosa kola run basic*
  # Run all kola tests (internal & external)
  $ cosa kola run --parallel 2
  

Overriding packages for testing

• If you need to override a file or a package for local testing, you can place those into the override/rootfs or override/rpm directory before building the image. See the Using overrides section from the COSA documentation.