Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 93)

Chapter 6.

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.

6.1. 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 (refer to the Ofﬁcial Red Hat Linux Customization

Guide for more information).

6.2. Standard Users

In Table 6-1, 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 Sec-

tion 6.4 for details on how groups are used.

User UID GID Home Directory Shell

root 0 0 /root /bin/bash

bin 1 1 /bin

daemon 2 2 /sbin

adm 3 4 /var/adm

lp 4 7 /var/spool/lpd

sync 5 0 /sbin /bin/sync

shutdown 6 0 /sbin /sbin/shutdown

halt 7 0 /sbin /sbin/halt

mail 8 12 /var/spool/mail

news 9 13 /var/spool/news

1 2 ... 88 89 90 91 92 93 94 95 96 97 98 ... 281 282

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Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 93