class bootstrap {

    class yum {

        package { [ "yum-priorities", "yum-fastestmirror"]:
            ensure => installed,
            before => File["/etc/yum/yum.conf"];
        }

        file { "/etc/yum/":
            ensure => directory,
            owner  => "root",
            group  => "root",
            purge  => true,
            mode   => 755,
        }

        (...)

    }

    class packages inherits yum {

        package {[
            "net-snmp",
            "net-snmp-utils",
(...)