Physical machines network boot in an network boot environment with DHCP/TFTP/DNS services or with poseidon/dnsmasq.
matchbox
serves iPXE or GRUB configs via HTTP to machines based on Group selectors (e.g. UUID, MAC, region, etc.) and machine Profiles. Kernel and initrd images are fetched and booted with Ignition to install CoreOS Container Linux. The "first boot" Ignition config if fetched and Container Linux is installed.
Container Linux boots ("first boot" from disk) and runs Ignition to provision its disk with systemd units, files, keys, and more to become a cluster node. Systemd units may fetch metadata from a remote source if needed.
Coordinated auto-updates are enabled. Systems like fleet or Kubernetes coordinate container services. IPMI, vendor utilities, or first-boot are used to re-provision machines into new roles.