Dry testing your manifest

Another useful command-line switch for puppet apply is the --noop option.
It instructs Puppet to refrain from taking any action on unsynced resources.
Instead, you only get a log output that indicates what will change without the switch. This is useful in determining whether a manifest would possibly break anything on your system:

root@puppetmaster:~# puppet apply puppet_service.pp --noop
Notice: Compiled catalog for puppetmaster.example.net in environment production in 0.63 seconds
Notice: /Stage[main]/Main/Service[puppet]/enable: current_value true, should be false (noop)
Notice: Class[Main]: Would have triggered 'refresh' from 1 events
Notice: Stage[main]: Would have triggered 'refresh' from 1 events
Notice: Applied catalog in 0.06 seconds  

The additional notices about triggered refreshes will be described later, and can be ignored for the moment. You will have a better understanding of their significance after finishing this chapter and Chapter 4, Combining Resources in Classes and Defined Types.