Managing and maintaining user accounts is the first step toward maintaining system security. Without indovidual user accounts, we would all be working on single large common directory, in a state of chaos. Managing user and group accounts allows us to partition and control the access of users with respect to one another

Managing users and groups is a larger part of your jobs as a system administrator. Setting up user accounts allows you to provide your users with access while still retaining the ability to track what your users do as well as the ability to limit their access as appropriate. It is one of the most visible jobs you'll have. Learning to do it efficiently will save you hours in the long run, and the confidence you'll exude from knowing it well will put you in good standing with your users.

Linux uses two or three files to maintain user and group information. The /etc/passwd file stores information about user accounts, and /etc/group stores information about groups. Most systems also use a file called /etc/shadow to maintain passwords. Later in the chapter you'll see examples of these files. You'll also see that all the basic administrative tasks of adding, removing, and modifying user and group accounts can be done in any of three ways: by manually editing the account's entry in /etc/passwd or /etc/group, by using Linux command-line utilitites that pass the relevant information to those files, or by using a GUI tool like Linuxconf to enter the same information.