The PMDF configuration file is the heart of the PMDF configuration. This main configuration file establishes the channels in use at a site and establishes which channels are responsible for which sorts of addresses via rewrite rules. Continuing the analogy of the previous section, the PMDF configuration file establishes the layout of the e-mail system by specifying the transport methods available (channels) and the transport routes (rewrite rules) associating types of addresses with appropriate channels.

Chapter 2 provides a detailed discussion of this file; an overview will be presented here.

Location

The PMDF configuration file is located via the logical PMDF_CONFIG_FILE (OpenVMS), the PMDF tailor file option PMDF_CONFIG_FILE (UNIX), or the Registry entry PMDF_CONFIG_FILE (NT). It is normally a file named pmdf.cnf, located in the PMDF table directory.²

Creation

The PMDF configuration file is normally initially created using the PMDF configuration utility, discussed in the PMDF Installation Guide. Alternatively, the file can be created entirely manually. Typically as site needs and configurations change, the PMDF postmaster will want to modify the PMDF configuration file, adding in new channels if new transport methods become available, fine tuning the operation of specific channels via numerous channel keyword optional settings, adding or changing rewrite rules as new systems are added or system names are changed.

Format overview

The PMDF configuration file is an ASCII text file that can be created or changed with a text editor. The configuration file should be world readable. Failure to make the configuration file world readable can cause unexpected PMDF failures.

The format of the configuration file consists of two parts: domain rewriting rules and the channel definitions. The domain rewriting rules appear first in the file and are separated from the channel definitions by a blank line. Each channel definition is separated from the following channel definition by a blank line.

Thus note that blank lines are significant in the PMDF configuration file: they delimit the end of the rewrite rules section of the file and separate channel definitions one from another.

Comment lines can appear anywhere in the configuration file. A comment is introduced with an exclamation point, !, in column one. Liberal use of comments to explain what is going on is strongly encouraged. Comment lines are ignored by the configuration file reading routines --- they are essentially "not there" as far as the routines are concerned and do not count as blank lines.

The contents of other files can be included in the PMDF configuration file using the < PMDF file include operator. Channel and rewrite rule definitions for PMDF layered products, for instance, are commonly incorporated into the main PMDF configuration file by reading subsidiary files into the main configuration file.

Use and operation

When a message enters the PMDF system it must be placed into the proper channel queue or queues for transport or delivery out that channel. PMDF's message enqueue routines consult the PMDF configuration file to determine this: the recipient addresses in the incoming message are each individually processed through the PMDF rewrite rules to determine the proper channel (route) for each, and message copies are then written to those corresponding channel queue areas. The rewriting process is also capable of changing the address, for instance, converting local host nicknames (short-form names in RFC 822 terminology) into fully qualified Internet style domain names.