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Puppet 4 Essentials, Second Edition

Puppet 4 Essentials, Second Edition

By : Felix Frank, Martin Alfke
3.7 (6)
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Puppet 4 Essentials, Second Edition

Puppet 4 Essentials, Second Edition

3.7 (6)
By: Felix Frank, Martin Alfke

Overview of this book

Puppet is a configuration management tool that allows you to automate all your IT configurations, giving you control over what you do to each Puppet Agent in a network, and when and how you do it. In this age of digital delivery and ubiquitous Internet presence, it's becoming increasingly important to implement scalable and portable solutions, not only in terms of software, but also the systems that run it. The free Ruby-based tool Puppet has established itself as the most successful solution to manage any IT infrastructure. Ranging from local development environments through complex data center setups to scalable cloud implementations, Puppet allows you to handle them all with a unified approach. Puppet 4 Essentials, Second Edition gets you started rapidly and intuitively as you’ll put Puppet’s tools to work right away. It will also highlight the changes associated with performance improvements as well as the new language features in Puppet 4. We’ll start with a quick introduction to Puppet to get you managing your IT systems quickly. You will then learn about the Puppet Agent that comes with an all-in-one (AIO) package and can run on multiple systems. Next, we’ll show you the Puppet Server for high-performance communication and passenger packages. As you progress through the book, the innovative structure and approach of Puppet will be explained with powerful use cases. The difficulties that are inherent to a complex and powerful tool will no longer be a problem for you as you discover Puppet's fascinating intricacies. By the end of the book, you will not only know how to use Puppet, but also its companion tools Facter and Hiera, and will be able to leverage the flexibility and expressive power implemented by their tool chain.
Table of Contents (10 chapters)
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9
Index

Retrieving and using Hiera values in manifests


Looking up a key value in Hiera is easy. Puppet comes with a very straightforward function for this:

$plugins = hiera('reporting::plugins')

Whenever the compiler encounters such a call in the manifest of the current agent node, it triggers a search in the hierarchy. The specific data sources are determined by the hierarchy in your hiera.yaml file. It will almost always rely on fact values provided by the agent to make flexible data source selections.

If the named key cannot be found in the agent's hierarchy, the master aborts the catalog compilation with an error. To prevent this, it is often sensible to supply a default value with the lookup:

$plugins = hiera('reporting::plugins', [])

In this case, Puppet uses an empty array if the hierarchy mentions no plugins. On the other hand, you can purposefully omit the default value. Just like with class and define parameters, this signals that the Hiera value is required. If the user fails to supply it...

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