The Kairos Factory

Kairos is not just an OS, it’s also a way to turn an existing OS into a Kairos-ready image. This process is called “Kairosification” and it’s done by the Kairos Factory.

For the newcomer or someone who simply needs an immutable OS with k3s and edgeVPN, the Kairos OS is the way to go. As long as this components work, you don’t need to worry about the changes in the underlying OS. However, if you need to ensure certain packages are present or remain stable in your system, you can use the Kairos Factory to convert your base image into a Kairos-ready image. This is particularly useful if you have special firmware requirements, or if you want to have your own release cadence.

Before we begin

In order to run the Kairos Factory, you will need docker and earthly installed on your system. You can find the installation instructions for both tools in the following links:

• Docker
• Earthly

And you must also clone the Kairos repository:

git clone https://github.com/kairos-io/kairos
cd kairos

The Kairos Factory Process

The process consists of three main steps:

1. Build your own base image
2. Feed your base image to the Kairos Factory
3. Consume your Kairos-ready artifacts

Examples

Pre-installing all firmware on a UKI image

If you need to pre-install all firmware on a UKI image, you can use the following Dockerfile:

FROM ubuntu:24.04
RUN apt-get update
RUN apt-get install -y --no-install-recommends \
    linux-image-generic-hwe-24.04
RUN apt-get clean && rm -rf /var/lib/apt/lists/*

Now we can build this image with Docker:

docker build -t my-base-image .

And then we can feed this image to the Kairos Factory:

earthly +base-image \
  --BASE_IMAGE=my-base-image \ # The image we just built
  --FAMILY=ubuntu \ # Kairos groups images by family, in this case Ubuntu has its own
  --FLAVOR=ubuntu \ # The flavor of the image, in this case Ubuntu
  --FLAVOR_RELEASE=24.04 \ # The release of the flavor
  --MODEL=generic \ # We are building for a generic model which can be used on a VM or hardware but not on a RPi or similar boards
  --VARIANT=core \ # We have standard images that comes with K3s, or core images that are just the base OS
  --BOOTLOADER=systemd-boot # The bootloader to use, in the case of UKI it has to be systemd-boot

Earthly will output an OCI artifact with a tag similar to quay.io/kairos/ubuntu:24.04-core-amd64-generic-v3.1.0. I’d recommend you re-tag this to something that makes sense to you.

docker tag quay.io/kairos/ubuntu:24.04-core-amd64-generic-v3.1.0 kairos-base-image

Now we can produce the UKI artifact that we will use to boot our machines:

earthly +uki-iso --BASE_IMAGE=kairos-base-image \
  --ENKI_KEYS_DIR=/path/to/keys

This will output an ISO file that you can use to boot your machines e.g.:

build/kairos_1040909.iso