Summary

After installing Puppet on your system, you can use it by writing and applying manifests. These manifests are written in Puppet's DSL and contain descriptions of the desired state of your system. Even though they resemble scripts, they should not be considered as such. For one thing, they consist of resources instead of commands. These resources are generally not evaluated in the order in which they have been written. An explicit ordering should be defined through the require and before metaparameters instead.

Each resource has a couple of attributes: parameters and properties. Each property is evaluated in its own right; Puppet detects whether a change to the system is necessary to get any property into the state that is defined in the manifest. It will also perform such changes. This is referred to as synchronizing a resource or property.

The ordering parameters, require and before, are of further importance because they establish dependency of one resource on one or more others. This allows Puppet to skip parts of the catalog if an important resource cannot be synchronized. Circular dependencies must be avoided.

Each resource in the manifest has a resource type that describes the nature of the system entity that is being managed. Some of the types that are used most frequently are file, package, and service. Puppet comes with many types for convenient system management, and many plugins are available to add even more. Some tasks require the use of exec resources, but this should be done sparingly.

In Chapter 2, Puppet Server and Agents, we will introduce the master/agent setup.