2.4. Installing a HTTP Server

Our Puppet module will install the packages necessary to run a HTTP server. This requires a resource definition that defines configurations for the httpd package.
In the module's manifests directory, create a new manifest file called httpd.pp: 
# touch mymodule/manifests/httpd.pp
This manifest will contain all HTTP configuration for our module. For organizational purposes, we will keep this manifest separate from the init.pp manifest.
Add the following content to the new httpd.pp manifest: 
class mymodule::httpd {
  package { 'httpd':
    ensure => installed,
  }
}
This code defines a subclass of mymodule called httpd, then defines a package resource declaration for the httpd package. The ensure => installed attribute tells Puppet to check if the package is installed. If it is not installed, Puppet executes yum to install it.
We also need to include this subclass in our main manifest file. Edit the init.pp manifest: 
class mymodule {
  include mymodule::httpd
}
It is now time to test the module. Run the following command: 
# puppet apply mymodule/tests/init.pp --noop
The puppet apply command applies the configuration in the manifest to your system. We use the test init.pp manifest, which refers to the main init.pp manifest. The --noop performs a dry-run of the configuration, which shows only the output but does not actually apply the configuration. The output should resemble the following: 
Notice: Compiled catalog for puppet.example.com in environment production in 0.59 seconds
Notice: /Stage[main]/Mymodule::Httpd/Package[httpd]/ensure: current_value absent, should be present (noop)
Notice: Class[Mymodule::Httpd]: Would have triggered 'refresh' from 1 events
Notice: Stage[main]: Would have triggered 'refresh' from 1 events
Notice: Finished catalog run in 0.67 seconds
The highlighted line is the result of the ensure => installed attribute. The current_value absent means that Puppet has detected the httpd package is not installed. Without the --noop option, Puppet would install the httpd package.