Managing Infrastructure with Puppet

Templates

Often you’ll want to maintain configuration files for applications that are different between servers. If you have a couple of configurations, it’s easy enough to maintain multiple files, but what if you have a very large number of differing configurations? We can manage this situation by writing ERB templates and populating the templates with node-specific information. This is done in Puppet with the template() function:

file { "apache-site":
    path => "/etc/apache2/sites-available/$fqdn",
    require => Package["apache2"],
    content => template("apache-site.erb"),
    notify => Exec["a2ensite"],
}

exec { "a2ensite $fqdn":
    notify => Service["apache2"],
    creates => "/etc/apache2/sites-enabled/$fqdn",
}

Here we have a file resource that creates an Apache config file named by the fqdn variable. We’ll assume that Facter is populating this variable with the fully qualified domain name of our server. The file contents are generated by an ERB template and then it notifies an exec that enables the site and notifies Apache to restart. Next we’ll write our template and place it in the expected location at /etc/puppet/templates/apache-site.erb:

<VirtualHost *:80>
    DocumentRoot /var/www/
    ServerName <%= name %>
    <Directory /var/www/>
        allow from all
        Options -Indexes
    </Directory>
</VirtualHost>

This is just a normal Apache vhost stanza, with the exception of the inline included name variable. All variables in the current scope are available to you in this manner and out-of-scope variables in other classes ...