Sample GRUB menu item to boot a CoreOS PXE image (assuming it is stored on the seventh GPT partition)

09_coreos.cfg

#!/bin/tail -n+2
menuentry 'CoreOS 1109.1.0' --class coreos --class gnu-linux --class gnu --class os --unrestricted {
	insmod part_gpt
	insmod fat
	set root='hd0,gpt7'
	linuxefi /coreos/vmlinuz-4.6.4-coreos kvm_intel.nested=1 coreos.autologin=tty1 coreos.configdrive=1
	initrdefi /coreos/coreos-1109.1.0.img
}