An ENC is a process that is run on the Puppet master or the host compiling the catalog, to determine which classes are applied to the node. The most common form of ENC is a script run through the exec node terminus. When using the exec node terminus, the script can be written in any language and it receives certname (certificate name) from the node, as a command-line argument. In most cases, this will be the Fully Qualified Domain Name (FQDN) of the node. We will assume that the certname setting has not been explicitly set and that the FQDN of our nodes is being used.

We will only use the hostname portion, as the FQDN can be unreliable in some instances. Across your enterprise, the naming convention of the host should not allow multiple machines to have the same hostname. The FQDN is determined by a fact; this fact is the union of the hostname fact and the domain fact. The domain fact on Linux is determined by running the hostname –f command. If DNS is not...