Hiera 1: Writing Data Sources

Hiera can use several different data backends, including two built-in backends and various optional backends. Each backend uses a different document format for its data sources.

This page describes the built-in yaml and json backends, as well as the puppet backend included with Hiera’s Puppet integration. For optional backends, see the backend’s documentation.

YAML

Summary

The yaml backend looks for data sources on disk, in the directory specified in its :datadir setting. It expects each data source to be a text file containing valid YAML data, with a file extension of .yaml. No other file extension (e.g. .yml) is allowed.

Data Format

See yaml.org and the “YAML for Ruby” cookbook for a complete description of valid YAML.

The root object of each YAML data source must be a YAML mapping (hash). Hiera will treat its top level keys as the pieces of data available in the data source. The value for each key can be any of the data types below.

Hiera’s data types map to the native YAML data types as follows:

Any string may include any number of variable interpolation tokens.

Example

---
# array
apache-packages:
    - apache2
    - apache2-common
    - apache2-utils

# string
apache-service: apache2

# interpolated facter variable 
hosts_entry: sandbox.%{fqdn}

# hash
sshd_settings: 
    root_allowed: "no"
    password_allowed: "yes"

# alternate hash notation
sshd_settings: {root_allowed: "no", password_allowed: "yes"}

# to return "true" or "false"
sshd_settings: {root_allowed: no, password_allowed: yes}
    

JSON

Summary

The json backend looks for data sources on disk, in the directory specified in its :datadir setting. It expects each data source to be a text file containing valid JSON data, with a file extension of .json. No other file extension is allowed.

Data Format

See the JSON spec for a complete description of valid JSON.

The root object of each JSON data source must be a JSON object (hash). Hiera will treat its top level keys as the pieces of data available in the data source. The value for each key can be any of the data types below.

Hiera’s data types map to the native JSON data types as follows:

Any string may include any number of variable interpolation tokens.

Example

{   
    "apache-packages" : [
    "apache2",
    "apache2-common",
    "apache2-utils"
    ],

    "hosts_entry" :  "sandbox.%{fqdn}",

    "sshd_settings" : {
                        "root_allowed" : "no", 
                        "password_allowed" : "no"
                      }
}

Puppet

Coming soon.

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