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Getting Started

Hiera is a simple hierarchal database which provides an easy to use interface for looking up data using a key.

$ hiera puppetlabs_home_page
http://puppetlabs.com

Installation

We are going to install Hiera using Rubygems, so now is a good time to make sure you meet the prerequisites.

Prerequisites

  • Ruby 1.8.5+
  • Rubygems 1.3.0+

Installing Hiera via Rubygems

$ gem install hiera
Successfully installed hiera-0.3.0
1 gem installed
Installing ri documentation for hiera-0.3.0...
Installing RDoc documentation for hiera-0.3.0...

Make sure we can run the hiera command:

$ hiera -v
0.3.0

Note: Some Linux distributions such as Debian squeeze do not put the gem bin directory (/var/lib/gems/1.8/bin) in your PATH by default. You may have to call hiera using the full path:

$ /var/lib/gems/1.8/bin/hiera -v
0.3.0

Configuration

Before using Hiera we need to create a configuration file. By default Hiera attempts to load hiera.yaml from the /etc/ directory. Lets create that file now:

$ vim /etc/hiera.yaml
---
:backends:
  - yaml

:hierarchy:
  - global

:yaml:
  :datadir: /var/lib/hiera/data

Note: If Hiera cannot locate /etc/hiera.yaml you will receive the follow error when trying to lookup a value:

$ hiera key
Failed to start Hiera: RuntimeError: Config file /etc/hiera.yaml not found

You can specify a different configuration file using the --config option:

$ hiera --config ~/hiera.yaml key

Adding data

With configuration out of the way, lets add some data. The yaml backend expects to find data files under the datadir we configured earlier.

Create the /var/lib/hiera/data data directory:

$ mkdir -p /var/lib/hiera/data

For each source in the hierarchy, the yaml backend will search for a corresponding YAML file under the datadir.

For example, our hierarchy consists of a single source named global. The yaml backend will look for /var/lib/hiera/data/global.yaml, and if missing skips it and move on to the next source in the hierarchy.

Lets add some data to the global source:

$ vim /var/lib/hiera/data/global.yaml
---
driftfile: '/etc/ntp/drift'
ntpservers:
  - '0.north-america.pool.ntp.org'
  - '1.north-america.pool.ntp.org'

Looking up data

Now that we have our configuration setup and some data, lets lookup the 'driftfile' key:

$ /var/lib/gems/1.8/bin/hiera driftfile
/etc/ntp/drift

We get extacaly what we expected, '/etc/ntp/drift'.

Running the lookup command with the --debug flag, we can see the details of how Hiera lookups data:

$ /var/lib/gems/1.8/bin/hiera driftfile --debug
DEBUG: Thu Jun 28 09:54:04 -0400 2012: Hiera YAML backend starting
DEBUG: Thu Jun 28 09:54:04 -0400 2012: Looking up driftfile in YAML backend
DEBUG: Thu Jun 28 09:54:04 -0400 2012: Looking for data source global
/etc/ntp/drift