We should be able to log in at the console of the discovery iso for the assisted installer. This can help with troubleshooting network configuration issues.

The Assisted Installer web GUI should have a prompt when generating the discovery iso to set a core user password next to the ssh public key.

All release of assisted installer   

This doc upstream shows how it can be done: https://github.com/openshift/assisted-service/blob/master/docs/set-discovery-password.md