Let's use the HOT hello world. The template can be passed to the Heat stack-create command as a local file, a URL to pull it from the network somewhere, or even as a Swift object if it was stored in Swift. It is important to validate a template. Pull down a copy of the template to your local filesystem.
Before you use this template, edit it and remove the constraints from admin_pass. It will make it easier to experiment with. Remove the lines under admin_pass that include constraints, length, and its description and both allowed_pattern and its description lines.
A template can be validated with Heat's template-validate command. Validating a template requires you to source a keystonerc file, use your overcloudrc file and then make sure that the template still validates with the changes you have made, as shown here:
undercloud# heat template-validate -f hello_world.yaml
Once the template validates, Heat will output a JSON representation of what it parsed from the template...
