Host provisioning format

Declare the first-boot format for host replacement and report installed observations.

Host images are opaque provider identifiers. A controller cannot reliably infer whether an image accepts cloud-init or Ignition from its name or the distribution currently running on the host.

Desired replacement configuration

Machine.spec.host.provisioningFormat declares CloudInit or Ignition for the desired host image. A versioned MachineConfiguration can also declare spec.template.host.provisioningFormat with its image.

spec:
  host:
    image: provider-specific-image-id
    provisioningFormat: CloudInit

For HostReplace, image and format are selected together from one configuration version and recorded in the operation target’s input.hostImage and input.provisioningFormat. Later Machine edits do not change this frozen pair.

Resolution follows these rules:

1. A Machine image overrides a template image. Whitespace-only image values count as absent; selected image identifiers have surrounding whitespace removed.
2. An explicit Machine provisioning format wins. When inheriting the template image, its declared format is used if the Machine has no format declaration. A Machine image override does not inherit a different template image’s format.
3. Otherwise the installed observation is used. A known Ignition installation selecting an explicit replacement image must declare the target format.
4. With neither a declaration nor an observation, CloudInit is the legacy fallback.

The controller currently generates cloud-init only. A resolved Ignition HostReplace fails before the destructive provider call. Declaring Ignition does not add controller-driven Ignition delivery. If an image changes provisioning format, declare the new target format explicitly rather than editing observations.

Operation snapshots created before the format field existed fall back to current Machine declarations/observations using their snapshotted image. They do not have the full frozen-format guarantee of newly initialized operations.

Installed observations

The agent accepts an optional ProvisioningFormat installation-config field with the values cloud-init or ignition. Explicit values are reported through Machine.status.observedProvisioningFormat, including on pre-created Machines. Status reporting preserves desired spec and uses the existing Machine status RBAC.

Omitted installation format remains unobserved. The agent does not infer it from the host OS and does not manufacture a CloudInit observation for a legacy host. Existing script/cloud-init renderers continue to leave that observation unset.

Deploy the updated CRDs and controller before agents that report explicit format observations. Older controllers do not enforce the new replacement protection; declaring a format is not sufficient protection while an older replacement controller still processes operations.