Using Heat template parameter value in bash script

Question

In a bash script in a Heat template, is it possible to use a parameter value from that template?

Answer 1

Yes, according to the Heat Orchestration Template specification, you can accomplish this with the str_replace function. They give an example that uses str_replace, together with get_param, to use a parameter value DBRootPassword in a bash script:

parameters:
  DBRootPassword:
    type: string
    label: Database Password
    description: Root password for MySQL
    hidden: true

resources:
  my_instance:
    type: OS::Nova::Server
    properties:
      # general properties ...
      user_data:
        str_replace:
          template: |
            #!/bin/bash
            echo "Hello world"
            echo "Setting MySQL root password"
            mysqladmin -u root password $db_rootpassword
            # do more things ...
          params:
            $db_rootpassword: { get_param: DBRootPassword }

Each key in params is replaced in template with its value. Since $db_rootpassword's value is set to the result of get_param, that means the parameter is passed into the bash script wherever $db_rootpassword is used.