The control of users and
groups exists at the core of Red Hat Linux system
administration.
Users can be either
actual people (accounts tied to a particular physical user) or logical
users (accounts that exist for applications so that they can do particular
things). Both types of users, actual or logical, have a User
ID and Group ID. User IDs are
usually unique (but don't have to be).
Groups are always logical expressions of
organization. Users make up groups, and groups form the foundation of
tying users together and giving them permissions to read, write, or
execute a given file.
Any file created is assigned a user and group when it is made, as well as
being assigned separate read, write, and execute permissions for the file's owner,
the group assigned to the file, and any other users on that host. The user
and group of a particular file, as well as the permissions on that file,
can be changed by root or, to a lesser extent, by the creator of the file.
Proper management of users and groups, as well as assigning and revoking
permissions, is one of the most important tasks of any system
administrator. Thankfully, Red Hat Linux makes this job as easy as possible while
preserving the security of the files on the host.
Managing users and groups has traditionally been tedious, but Red Hat Linux
provides a few tools and conventions to make users and groups easier to
manage.
While you can use useradd to create a new user from
the shell prompt, a popular way to manage users and groups is through
Linuxconf (see the
Official Red Hat Linux Customization Guide for details on
Linuxconf).
