The Image Builder project currently defines how to build a specific image in Go code. This proved to be troublesome for many reasons:

• Image maintainers from outside the team have a hard time figuring out how to make a change in the definitions because the code is too complex.
• Changing the definitions requires a time-consuming rebuild of the Go code.
• Tight coupling osbuild-composer and the definitions means that we have to redeploy composer every time we want an image definition to be updated. Since osbuild-composer is a big project, there's always a risk that something unrelated will break.

The goal of this feature is to create a new project called OTK that allows defining images in YAML-based omnifests files. This brings several benefits:

• We believe that a YAML-based DSL is easier to read than Go.
• Compiling an omnifest is way faster than compiling a Go code.
• It's possible to update image definitions separately from osbuild-composer.

The project homepage: https://github.com/osbuild/otk

Acceptance criteria

• OTK is implemented and tested.
• The omnifest format is defined.
• Omnifests that build the same CentOS Stream 9 images as osbuild/images do are implemented.
  • Out of scope: Integration between osbuild-composer, images and otk, this is a separate feature: COMPOSER-2290.