# ADR 1 — Base image Status: accepted ## Context Corium needs an immutable base in the CoreOS/OSTree lineage. Its configuration surface is cloud-init. Fedora CoreOS was the obvious starting point. It is the mature member of the lineage, and its install tooling is excellent (`coreos-installer`, live ISO, PXE). We verified three things before we made a decision on it. - Ignition fragments that the image provides in `/usr/lib/ignition/base.d/` work, and with the correct precedence. Ignition merges the user's configuration *over* the image's configuration. The plumbing in the image thus applies where the operator says nothing, and it never overrides the operator. We confirmed this in `internal/exec/engine.go` in `coreos/ignition`, not in the documentation. - FCOS boots with no Ignition configuration at all. The maintainers refused to make a missing configuration fatal: *"Today, we happily boot and sit there if the user doesn't provide Ignition"* (`fedora-coreos-tracker#279`). Thus a node that uses only cloud-init is possible. - Zincati, the auto-update agent of FCOS, fails on OCI-native deployments. You must mask it. So the design was possible to build. The question was whether to build it. ## Decision Base on `quay.io/fedora/fedora-bootc`. ## Consequences FCOS is Ignition-native. To use cloud-init as the primary surface on FCOS, we must do three things: - Mask Zincati. - Neutralize the SSH key injection of Afterburn. Afterburn overlaps the metadata role of cloud-init. If both run, two agents race to provision the same user. - Arbitrate between NetworkManager and the network stage of cloud-init. That is a large amount of work, and its result is the place where `fedora-bootc` already is. The ecosystem already made this choice. `ucore`, the most developed FCOS derivative, stays on Ignition. `k0snode-bootc` runs k0s on bootc with cloud-init, and it starts from a generic bootc base, not from FCOS. No project ships FCOS with cloud-init as its primary surface. Also, FCOS itself is moving to bootc (`fedora-coreos-tracker#2214`, targeting Fedora 46). When we start from `fedora-bootc`, we start where FCOS is going. What we give up: the install tooling of FCOS and its server base, which has much testing in production. `bootc-image-builder` replaces the first. It makes an installable artifact directly from the image. FCOS needs two steps: you install a stock image, then you rebase onto ours.