Chapter 2 Users And Groups; Tools For User And Group Administration; Standard Users - Red Hat LINUX 7.2 Reference Manual

Section 2.2:Standard Users
2 Users and Groups
The control of users and groups exists at the core of Red Hat Linux system administration.
Users can be either people (accounts tied to a physical user) or logical users (accounts that exist for
applications so that they can perform specific tasks) . Both types of users have a User ID (which is
usually unique) and Group ID.
Groups are logical expressions of organization. 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. It is also 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.

2.1 Tools for User and Group Administration

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 redhat-config-users (see the Official Red Hat Linux Customization Guide
for more information).

2.2 Standard Users

In Table 2–1, Standard Users, you will find the standard users set up by the installation process (as
seen in the /etc/passwd file). The Group ID (GID) in this table is the primary group for the user.
See Section 2.4, User Private Groups for details on how groups are used.
Table 2–1 Standard Users
User
root
bin
daemon
adm
UID GID Home Directory
0 0 /root
1 1 /bin
2 2
/sbin
/var/adm
3 4
Shell
/bin/bash
27