netboot.xyz/docs/boot-loaders.md

Boot as iPXE Linux Kernel

The ipxe.lkrn file can be booted as a Linux kernel from the bootloader. This can be useful for providing a diagnostic tool as part of the OS or even having a quick option to reprovision the server on the fly.

Extlinux

Edit /boot/extlinux.conf and add a simple entry:

LABEL ipxe-boot
      kernel /boot/ipxe.lkrn
      initrd /boot/ipxe-config.ipxe

The kernel is treated as a Linux kernel and the initrd is treated as the iPXE script that is run once the kernel has loaded.

Grub