Introducing variables

A variable in Puppet is simply a way of giving a name to a particular value, which we can then use wherever we would use the literal value (variable_string.pp):

$php_package = 'php7.0-cli'

package { $php_package:
  ensure => installed,
}

The dollar sign ($) tells Puppet that what follows is a variable name. Variable names must begin with a lowercase letter or an underscore, though the rest of the name can contain uppercase letters or numbers as well.

A variable can contain different types of data—one such type is a String (like php7.0-cli), but Puppet variables can also contain Number values, or Boolean values (true or false). Here are a few examples (variable_simple.pp):

$my_name = 'Zaphod Beeblebrox'
$answer = 42
$scheduled_for_demolition = true

Using Booleans

Strings and numbers are straightforward, but Puppet also has a special data type to represent true or false values, which we call Boolean values, after the logician George Boole. We have already encountered some...