12   exec { "newaliases":
   13     command => "/usr/bin/newaliases",
   14     require => [
   15       File["/etc/aliases"],
   16       Package["postfix"]],
   17     onlyif  => "/usr/bin/test /etc/aliases -nt /etc/aliases.db",
   18     subscribe => File["/etc/aliases"],
   19   }