# ADR 1 — Base image Status: accepted ## Context Corium needs an immutable base in the CoreOS/OSTree lineage, and exposes cloud-init as its configuration surface. Fedora CoreOS was the obvious starting point: it is the mature member of the lineage, with excellent install tooling (`coreos-installer`, live ISO, PXE). Three things were verified before ruling on it. - Image-provided Ignition fragments in `/usr/lib/ignition/base.d/` work, and with the right precedence. Ignition merges the user's config *over* the image's, so baked-in plumbing applies wherever the operator is silent and never overrides them. Confirmed in `internal/exec/engine.go` in `coreos/ignition`, not from documentation. - FCOS boots with no Ignition config at all. Maintainers declined to make its absence fatal: *"Today, we happily boot and sit there if the user doesn't provide Ignition"* (`fedora-coreos-tracker#279`). A cloud-init-only node is therefore possible. - Zincati, FCOS's auto-update agent, fails on OCI-native deployments and must be masked. So the design was buildable. The question was whether it should be built. ## Decision Base on `quay.io/fedora/fedora-bootc`. ## Consequences FCOS is Ignition-native. Running cloud-init as the primary surface there means masking Zincati, neutralising Afterburn's SSH key injection — it overlaps cloud-init's metadata role, and running both gives two agents racing to provision the same user — and arbitrating between NetworkManager and cloud-init's network stage. That is a meaningful amount of work whose endpoint is the place `fedora-bootc` already occupies. The ecosystem has drawn this line already. `ucore`, the most developed FCOS derivative, stays on Ignition. `k0snode-bootc`, which runs k0s on bootc with cloud-init, starts from a generic bootc base rather than FCOS. No project ships FCOS with cloud-init as its primary surface. Finally, FCOS is itself converging on bootc (`fedora-coreos-tracker#2214`, targeting Fedora 46). Starting from `fedora-bootc` is starting where FCOS is going. What is given up: FCOS's install tooling and its battle-tested server base. `bootc-image-builder` covers the first, producing an installable artefact directly from the image rather than FCOS's two-step of installing a stock image and rebasing onto ours.