This repo holds custom dracut modules required by Fedora and RHEL CoreOS for Ignition to work properly.
It's packaged on Fedora together with Ignition in the ignition package.
The easiest way to test it out is to pick up the latest Fedora CoreOS preview artifact from:
https://getfedora.org/coreos/download/
You can see an example of how to pass a config on qemu at least in coreos-assembler:
https://github.com/coreos/coreos-assembler/blob/master/src/cmd-run
Note that a lot of things are in flux and subject to rapid change. E.g. some key names have changed wrt their equivalents in CoreOS Container Linux.