use a custom ipxe script with tinkerbell hardware.yaml

hw.yaml

apiVersion: tinkerbell.org/v1alpha1
kind: Hardware
metadata:
  annotations:
  name: "pxe-uefi"
  namespace: tink-system
spec:
  disks:
  - device: /dev/nvme0n1
  interfaces:
  - dhcp:
      arch: x86_64
      hostname: pxe-uefi
      ip:
        address: 192.168.2.158
        gateway: 192.168.2.1
        netmask: 255.255.255.0
      lease_time: 86400
      mac: 52:54:00:ee:0d:0b
      name_servers:
      - 1.1.1.1
    netboot:
      allowPXE: true
      allowWorkflow: true
  metadata:
    facility:
      facility_code: onprem
    instance:
      hostname: pxe-uefi
      id: 52:54:00:ee:0d:0b
      # userdata must start with `#!ipxe`: https://github.com/tinkerbell/boots/blob/aee8a507b6f3d069f7dfa41f921eb1130342dfff/installers/customipxe/main.go#L44
      userdata: |
        #!ipxe
        echo this is a custom ipxe script
        shell
      # if userdata is set, ipxe_script_url is not used. https://github.com/tinkerbell/boots/blob/aee8a507b6f3d069f7dfa41f921eb1130342dfff/installers/customipxe/main.go#L46
      ipxe_script_url: https://boot.netboot.xyz
      operating_system:
        distro: custom_ipxe
    manufacturer:
      slug: libvirt