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Postfix: The Definitive Guide by Kyle D. Dent

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Chapter 2. Prerequisites

This chapter presents some basic Unix and email concepts that you need in order to follow explanations and examples presented later in the book. If you are already familiar with email administration, you can safely skip the material here and move on to the next chapter. This chapter does not give a systematic or comprehensive overview of either email or Unix administration. There is already an enormous amount of information available on both topics. This chapter simply presents an assortment of items that are referred to later in the book, with the expectation that readers already understand them.

Unix Topics

There's no question that the more familiar you are with Unix, the better a Postfix administrator you'll be. Postfix is very much a Unix program working in conjunction with the underlying operating system for many of its functions. If you're new to Unix, you should study an introductory text. In the meantime, this section presents some fundamental concepts that you will need to understand to follow explanations in the book.

Login Names and UID Numbers

The list of recognized users on a system is stored in the /etc/passwd file. Every user should have a unique login name and user ID number (commonly written as uid or UID). The UID, not the user's login name, is the important attribute for identity and ownership checks. The login name is a convenience for humans, and the system uses it primarily to determine what the UID is. Some Postfix configuration parameters ...

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