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OS metadata and agent identity

The agent needs to derive its own identity from several aspects of the underlying OS. In order to do so, at startup it performs run-time introspection of current machine state and OS metadata.

The following details are derived from the host environment:

  • application-specific node UUID
  • base architecture
  • update stream
  • OS platform
  • OS version
  • OSTree revision

It is thus required that the OS provides those values in the locations described below.

Kernel command-line

Kernel command-line must contain a ignition.platform.id=<VALUE> argument. The literal value is used as the “OS platform”.

rpm-ostree deployment status

Booted deployment must provide several mandatory metadata entries:

  • checksum: OSTree commit revision
  • version: OS version
  • under base-commit-meta:
    • coreos-assembler.basearch: base architecture
    • fedora-coreos.stream: update stream

All those metadata entries must exist with a non-empty string value.

Filesystem

Filesystem must provide a /etc/machine-id file, as specified by machine-id spec. Its value is used to derive the application-specific node UUID.