Parameterized classes are classes in which you have defined several parameters that can be overridden when you instantiate the class for your node. The use case for parameterized classes is when you have something that won't be repeated within a single node. You cannot define the same parameterized class more than once per node. As a simple example, we'll create a class that installs a database program and starts that database's service. We'll call this class example::db; the definition will live in modules/example/manifests/db.pp, as follows:
class example::db ($db) {
case $db {
'mysql': {
$dbpackage = 'mysql-server'
$dbservice = 'mysqld'
}
'postgresql': {
$dbpackage = 'postgresql-server'
$dbservice = 'postgresql'
}
}
package { "$dbpackage": }
service { "$dbservice":
ensure => true,
enable => true,
require => Package["$dbpackage"]
}
}This class takes a single parameter ($db) that specifies the...