You must have a working GRUB installation already, if not checkout the Preparations for Boot .
Why would you need this? When you don't have a KVM or just don't want to use ILO, iDRAC, iPMI or other management tools to mount an ISO.
This snippet is from a try to install Fedora CoreOS from an ISO file named
install.io from the
grub.cfg contents (
coreos.inst.install_dev=sda would use the
sda device for installation in case of *CoreOS):
1 2 3 4 5 6 7 8 9 10
It worked fine though the original case was to load the Ignition file from the boot disk which didn't work, a Webserver / Matchbox server was required to load the Ignition file from.