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Lemur zaprasza

Red Hat® Linux 6 Unleashed

Chapter 20: Essential System Administration

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Sections in this Chapter:

Handling
the All-Powerful root Account

Adding
a User with a Configuration Tool

Maintaining
the System--Implementing Changes

Adding
Users

The Login
and How to Become a Specific User

Getting
Help

Changing
User Properties

Searching
for User's Information

Problem Solving--Logs

Temporarily
Disabling a User

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Problem Solving--Logs

Other Files That
Deny or Allow Users or Hosts

Many times, when
trying
to diagnose a problem, it is helpful to look at log files of various
activities. As an example, consider the following
scenario.You are the administrator of a server
connected to the Internet. When you try to log in with your user ID (after all,
you don't log in as root but
su to root), you find
that you cannot log in.Perhaps the problem is as
simple
as mistyping your password. In this case, a simple second attempt at logging in
will fix the problem. Of course, if that were the problem, you wouldn't be
reading this book.Perhaps you forgot your password.
This is a common error, especially when a password has just been
changed.

Note -
Writing down new passwords is not a good idea because it gives other people
access to your account.

For a forgotten password, you could simply log in as
root (or get the system administrator) and change
the password.Perhaps someone logged on to your system
as you and changed your password. How would you
know
this? This is where logs come in handy. You can examine certain logs, depending
upon the information needed. Probably the first file to check is
/var/log/messages. This file shows a great deal of
information. For the benefit of the example, though, look for lines that say
something like this:

Jun 10 21:54:37 lolly PAM_pwdb[622]: Check pass; user unknown
Jun 10 21:54:37 lolly login[622]: FAILED LOGIN 1 FROM (null) FOR george, \
User not known to the underlying authentication module

Other Files That Deny or Allow Users or Hosts
Another file that will deny hosts
from accessing the computer is the /etc/hosts.deny
file. The hosts.deny file describes the names of
the hosts that are not allowed
to use the local INET services.