Learning Puppet - II: Applying Classes

In my previous post about learning Puppet, I left a few open questions that I will attempt to answer as I continue learning.

1. How can I apply Puppet classes?
2. How can I install modules?
3. How can I define functions in Puppet?

In the last post, I was unable to apply a class so I moved ahead without it. Let us look at that in this post.

To apply a class, I created a module, created its init.pp file and added a class in it.

Let us consider the module name to be mod. The init.pp will be located at mod/manifests/init.pp. I just keep it empty to begin with. The name of the class in that file has to match the module name though.

class mod{
}

Moving on to create a class of interest, let us add one to install Openjdk. The file would be mod/manifests/jdk.pp.

class mod::jdk () {
  notice("Installing openJDK")
  # Install java
  package { 'openjdk':
    ensure => installed,
    name => 'java-1.8.0-openjdk-headless',
    alias => 'openjdk',
  }
}

To apply the manifest, the command would be as follows:

puppet apply --modulepath=/path/to/parent/of/module -e "include mod::jdk"