convenient ability to just boot a coreos node with custom butane/ignition

I've had this desire a few times myself, most recently I wanted to point some users at this in https://issues.redhat.com/browse/OCPBUGS-1327

Basically when one wants to debug an IPI issue, it'd be really, really useful to have something like:

openshift-install provision-one-coreos --with-butane foo.bu

(And --with-ignition foo.ign)

That would use the relevant bits of the install-config.yaml and run through all the same Terraform setup code to set up basically the same flow for the bootstrap node and...that's it. The user would normally put a SSH key in the install config for this. (But with --with-butane one could inject one easily, alongside any other desired config)

This would make it much easier to debug e.g. networking issues between instances, verify hardware works etc. without entirely dropping to fully custom UPI.

Start at the openshift-install CLI entry point and trace the Terraform setup code used for the bootstrap node. Check how install-config.yaml supplies the existing provisioning settings, then determine how the proposed Butane and Ignition inputs should enter that flow. Done means a command can provision one CoreOS node using the existing setup path for debugging.