template.json

{
    "builders": [{
        "type": "openstack",
        "name": "rackspace-public",
        "region": "DFW",
        "username": "USERNAME",
        "password": "PASSWORD",
        "openstack_provider": "rackspace",
        "identity_endpoint": "https://identity.api.rackspacecloud.com/v2.0",

        "source_image": "54b9efe7-af0b-4022-a5e9-05a6cd4c082d",
        "flavor": "8",
        "image_name": "MYIMAGE",
        "user_data_file":"./winrm-init.ps1",
        "communicator": "winrm",
        "winrm_username": "Administrator",
        "winrm_use_ssl": true,
        "winrm_insecure": true,
        "winrm_timeout": "5m"
    }]
}