k0s bootc

This repo contains the recipes to build a bootable container image based on bootc for k0s.

What is...

...k0s?

k0s is an open source, all-inclusive Kubernetes distribution, which is configured with all of the features needed to build a Kubernetes cluster and packaged as a single binary for ease of use.

You can find more information about k0s here.

...bootc?

Do you know what a container is? Well, a container image doesn't contain a kernel; so container image + kernel = bootable container image. The obtained bootable container image can be run on a VM or a bare-metal machine, with the advantage of a highly customizable immutable OS built exploiting traditional OCI tools(e.g. podman) and skills.

To make this magic happen, we use bootc.

Transactional, in-place operating system updates using OCI/Docker container images. bootc is the key component in a broader mission of bootable containers.

Image tags semantics

In the registry, different tags for each image are available.

• latest is the latest compiled version of the image (it may not be a good idea to use it in production).
• dev is the latest compiled development version of the image. It would be unstable.
• X.Y.Z-k0s.N-SHORT_SHA is the image compiled from the git commit corresponding to the SHORT_SHA (e.g 1.32.1-k0s.0-7b3b3d1). It may be associated with a development commit.
• X.Y.Z-k0s.N is the latest compiled image with the specified k0s version (e.g 1.32.1-k0s.0).
• X.Y.Z is the latest compiled image with the specified k8s compatible version of k0s (e.g 1.32.1).
• X.Y is the latest compiled image with the equivalent major and minor k8s compatible version of k0s (e.g 1.32).

If you want to understand better the k0s versioning, you can find more information here.

Build

To build a bootable container image no special requirements are needed, just build it as an ordinary container image with podman or buildah.

podman build -t k0s-bootc:${IMAGE_TAG} .

For the use in production, you should use the image built by the CI/CD pipeline. It will publish the image to the github registry.

Installation

There are several ways to deploy a new instance of this machine. You can refer to the fedora bootc docs to find the most suitable way to deploy your machine.