The playbook supports self-building of various components, which don't have a container image for your architecture (see the [container images we use](container-images.md)). For `amd64`, self-building is not required.
For other architectures (e.g. `arm32`, `arm64`), ready-made container images are used when available. If there's no ready-made image for a specific component and said component supports self-building, an image will be built on the host. Building images like this takes more time and resources (some build tools need to get installed by the playbook to assist building).
To make use of self-building, you don't need to do anything. If a component has an image for the specified architecture, the playbook will use it directly. If not, it will build the image on the server itself.
If you'd like **to force self-building** even if an image is available for your architecture, look into the `matrix_*_self_build` variables provided by individual roles.
