Linux Journal March 2015 by Linux Journal

Author:Linux Journal
Language: eng
Format: mobi, epub
Tags: Encryption, Hiera, lightweight, Android, systemd, encrypt, X60, init systems, ODE, Libreboot, BusyBox, $29 tablet, New Clues, ordinary differential equations, Model Builder, Bluetooth Auto Connect, virtual containers, Nmap, MenuMeters, Puppet, SSH, Linux, cards, Cluetrain Manifesto, Acey-Deucey
Publisher: Belltown Media
Published: 2015-02-25T08:00:00+00:00

:backends:

- yaml

:yaml:

:datadir: /etc/puppet/hieradata

:hierarchy:

- "node/%{::fqdn}"

- "environment/%{::env}/main"

- "environment/%{::env}/%{calling_module}"

- defaults

And a yaml file:

/etc/puppet/hieradata/environment/prod/main.yaml:

---

$nginx::credentials::basic_auth: 'password'

Hiera can have multiple back ends, but for now, let’s start with yaml, which is the default and requires no additional software. The :datadir: is just the path to where the hierarchy search path should begin, and is usually a place within your Puppet configuration. The :hierarchy: section is where the core algorithm of how Hiera does its key/value lookups is defined. The :hierarchy: is something that will grow and change over time, and it may become much more complex than this example.

Within each of the paths defined in the :hierarchy:, you can reference any Puppet variable, even $operatingsystem and $ipaddress, if set. Using the %{variable} syntax will pull the value.

This example is actually a special hierarchical design that I use and recommend, which employs a fact assigned to all nodes called @env from within facter. This @env value can be set on the hosts either based on FQDN or tags in EC2 or elsewhere, but the important thing is that this is the separation of one large main.yaml file into directories named prod, dev and so on, and, therefore, the initial separation of Hiera values into categories.

The second component of this specific example is a special Hiera variable called %{calling_module}. This variable is unique and reserved for Hiera to indicate that the yaml filename to search will be the same as the Puppet module that is performing the Hiera lookup. Therefore, the way this hierarchy will behave when looking for a variable in Puppet is like:

$nginx::credentials::basic_auth

First, Hiera knows that it’s looking in /etc/puppet/hieradata/node for a file named <hostname.domain.tld>.yaml and for a value for nginx::credentials::basic_auth. If either the file or the variable isn’t there, the next step is to look in /etc/puppet/hieradata/environment/<prod|stage|dev>/main.yaml, which is a great way to have one yaml file with most of your Hiera values. If you have a lot of values for the nginx example and you want to separate them for manageability, you simply can move them to the /etc/puppet/hieradata/environment/<prod|stage|dev>/nginx.yaml file. Finally, as a default, Hiera will check for the value in defaults.yaml at the top of the hieradata directory.

Your Puppet manifest for this lookup should look something like this:

modules/nginx/manifests/credentials.pp

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