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Architecture

Boot Operator mainly consists of the a set webservers and controllers working together to fulfill the requirement of the boot process of the Baremetal machines.

Kubernetes API

Following are the Kubernetes CR and related controllers used to manage the boot infrastructure of the baremetal servers.

  • IPXEBootConfig

    • The purpose of this CR and related controller is to allow users to configure the system to provide customised ipxe-script replies to the requests made by the baremetal servers.
    • It allows users with references tailored ignition content, and customised ipxe-scripts to the related IPXEBootConfig object.
    • There is usually a single IPXEBootConfig object corresponding to each of the baremetal servers.

  • HTTPBootConfig

    • The purpose of this CR and related controller is to allow users to configure the system to provide customised httpboot replies to the requests typically made by the DHCP servers.
    • It allows users to reference the ignition content and customised ukiURL.

Architectural Diagrams

Diagram1

Diagram2

Workflow

Although the components of Boot Operator can function independently, this section describes a typical usecases of how they work together.

  • IPXE Workflow

    • The IPXE workflow involves a DHCP server (e.g., FeDHCP) and the Boot Operator deployment with the necessary IPXE configuration flags.
    • When a bare metal server boots with the IPXE network option, it requests the /ipxe endpoint from the IPXE web server within the Boot Operator deployment via dhcp server. The server receives the IPXE script configured in the corresponding IPXEBootConfig object.
    • The server then fetches the Ignition content from the /ignition endpoint, as specified in the IPXE script and the configured Ignition content for the server.

  • HTTPBoot Workflow

    • The HTTPBoot workflow involves a specialized DHCP server (e.g., FeDHCP), the Boot Operator with HTTPBoot configuration enabled, and a UKI OS image hosted on a web server or registry.
    • When a bare metal server boots with the HTTPBoot option, it contacts the FeDHCP server, which returns the UKI image location from the external web server. FeDHCP internally uses the /httpboot endpoint exposed by the Boot Operator, fetching the required information from the related HTTPBootConfig object.
    • The server can then retrieve the Ignition content from the /ignition endpoint, as configured for the desired OS.