ch06.htm

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
<SCRIPT>
<!--
function displayWindow(url, width, height) {
        var Win = window.open(url,"displayWindow",'width=' + width +
',height=' + height + ',resizable=1,scrollbars=yes');
}
//-->
</SCRIPT>
</HEAD>

 -->



 





 








<H1></H1>



<UL>

	<LI><A HREF="#Heading1">- 6 -</A>

	<UL>

		<LI><A HREF="#Heading2">Getting Started</A>

		<UL>

			<LI><A HREF="#Heading3">Starting (and Stopping!) Your Linux System</A>

			<LI><A HREF="#Heading4">WARNING</A>

			<UL>

				<LI><A HREF="#Heading5">Whats This About Logging In?</A>

			</UL>

			<LI><A HREF="#Heading6">NOTE</A>

			<LI><A HREF="#Heading7">NOTE</A>

			<LI><A HREF="#Heading8">NOTE</A>

			<UL>

				<LI><A HREF="#Heading9">Why You Shouldnt Use the root Login</A>

			</UL>

			<LI><A HREF="#Heading10">WARNING</A>

			<LI><A HREF="#Heading11">NOTE</A>

			<UL>

				<LI><A HREF="#Heading12">Your First Login</A>

			</UL>

			<LI><A HREF="#Heading13">NOTE</A>

			<LI><A HREF="#Heading14">Passwords</A>

			<LI><A HREF="#Heading15">NOTE</A>

			<LI><A HREF="#Heading16">WARNING</A>

			<LI><A HREF="#Heading17">WARNING</A>

			<LI><A HREF="#Heading18">TIP</A>

			<LI><A HREF="#Heading19">Creating a New Login</A>

			<LI><A HREF="#Heading20">TIP</A>

			<LI><A HREF="#Heading21">NOTE</A>

			<LI><A HREF="#Heading22">Logging Out</A>

			<LI><A HREF="#Heading23">Trying Out Your New Login</A>

			<LI><A HREF="#Heading24">NOTE</A>

			<UL>

				<LI><A HREF="#Heading25">Linux Error Messages</A>

				<LI><A HREF="#Heading26">Search Paths</A>

			</UL>

			<LI><A HREF="#Heading27">Virtual Terminals</A>

			<LI><A HREF="#Heading28">Commands and Programs</A>

			<LI><A HREF="#Heading29">Summary</A>

		</UL>

	</UL>

</UL>



<P>

<HR SIZE="4">



<H2 ALIGN="CENTER"><A NAME="Heading1<FONT COLOR="#000077">- 6 -</FONT></H2>

<H2 ALIGN="CENTER"><A NAME="Heading2<FONT COLOR="#000077">Getting Started</FONT></H2>

<P><I>by Ed Treijs</I></P>

<P>IN THIS CHAPTER</P>



<UL>

	<LI>Starting (and Stopping!) Your Linux System

	<P>

	<LI>Passwords

	<P>

	<LI>Creating a New Login

	<P>

	<LI>Logging Out

	<P>

	<LI>Trying Out Your New Login

	<P>

	<LI>Virtual Terminals

	<P>

	<LI>Commands and Programs

</UL>



<P><BR>

Congratulations! Now that you have successfully installed Linux, you can start using

it. In this chapter we will look at the steps you need to take to begin working with

Linux, including the following:



<UL>

	<LI>Starting and stopping Linux

	<P>

	<LI>Logging in and out

	<P>

	<LI>Creating a new user with <TT>adduser</TT>

	<P>

	<LI>Changing your password

	<P>

	<LI>Using virtual terminals

	<P>

	<LI>Displaying system users with <TT>who</TT>

</UL>



<H3 ALIGN="CENTER"><A NAME="Heading3<FONT COLOR="#000077">Starting (and Stopping!)

Your Linux System</FONT></H3>

<P>Depending on the setup you chose during Linux installation and configuration,

either Linux starts automatically when you power on your computer, or it requires

you to type something (such as <TT>Linux</TT>) to specify that you want to boot Linux.</P>

<P>As your Linux system starts up, you see quite a few Linux initialization messages

scroll through your screen. When Linux has completed its startup, you should see

the following prompt:</P>

<PRE><FONT COLOR="#0066FF">Welcome to Linux 2.0.0.



darkstar login:

</FONT></PRE>



<DL>

	<DT><FONT COLOR="#0066FF"></FONT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading4<FONT COLOR="#000077"><B>WARNING:</B> </FONT>A Linux system

	must always be shut down properly. Improper shutdown, such as simply turning off

	your system, can cause serious damage to your Linux system! When you are finished

	using your Linux system, you must shut it down properly, as described in the next

	section. If you start to boot Linux, and then change your mind, you should let the

	system start up fully and then follow the shutdown procedure. 

<HR>



</DL>



<P>Because you know how to start Linux, it's even more important to know how to shut

it down properly. Like many UNIX systems, if Linux is not powered down properly,

damage to files can result. The easiest way to ensure a proper shutdown is to press

the Ctrl, Alt, and Delete keys simultaneously. (This is the famous Ctrl-Alt-Delete

&quot;three-finger salute&quot; used in DOS.)</P>

<P>Pressing Ctrl-Alt-Delete causes a number of advisory messages and Linux shutdown

messages to be displayed. You must wait until the Linux shutdown procedure has finished,

at which point your monitor shows the initial &quot;power-on&quot; screen, before

turning your computer off.

<H4 ALIGN="CENTER"><A NAME="Heading5<FONT COLOR="#000077">Whats This About

Logging In?</FONT></H4>

<P>Linux waits for a login. A login is simply the name that you supply to Linux to

identify yourself to the operating system. Linux keeps track of which names are permitted

to log in or access the system, and only allows valid users to have access.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading6<FONT COLOR="#000077"><B>NOTE: </B></FONT>If you supplied

	a name to your system when installing Linux, the system name is used at the prompt.

	In the login shown earlier, the system has been called <TT>darkstar</TT>. The system

	name enables you to identify your machine to others when using networks or modem

	connections. Don't worry if you didn't name your system yet, because you can change

	the system's name at any time. 

<HR>



</DL>



<P>Every login name on the system is unique. Normally, a password is assigned to

each login, too. This secret password is like the identification number you use with

your bank card to prove that you really are who you say you are. Also, the things

you can do with your login--the login's privileges--are controlled by Linux; different

logins have different levels of privileges.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading7<FONT COLOR="#000077"><B>NOTE: </B></FONT>Usually, login names

	reflect a person's real name. Although you can't have two identically named logins

	on your system, you can easily create logins for users with the same (real) name

	by having one or two characters different. So, for example, the login names <TT>suej</TT>

	and <TT>suek</TT> are treated by Linux as completely separate logins. Conversely,

	there is no reason that one human being (for instance, yourself) can't have two,

	three, or a dozen login names. In fact, because you will be the system administrator

	of your Linux system, you will have one or more administrative logins, and one or

	more regular user logins. 

<HR>



</DL>



<P>At the login prompt, try typing your name, your dog's name, or any other random

name that occurs to you. None of these are valid logins (at least not yet). The system

asks you for a password; it won't matter what you type, so just press Enter or type

a random string of characters. Because the logins are not valid on the system, Linux

won't let you in. It displays the message <TT>Login incorrect</TT> to tell you that

either the name or the password you entered is not valid.</P>

<P>The only valid login on your Linux system after installation is the most powerful

and dangerous login Linux offers: <TT>root</TT>. In the section &quot;Creating a

New Login,&quot; later in this chapter, we will create a safe login for you to use.

This login can have your name, your dog's name, or whatever else you choose.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading8<FONT COLOR="#000077"><B>NOTE:</B> </FONT>The login prompt

	is actually produced by a program called <TT>login</TT> whose only task is to accept

	your user ID and password, verify it, and then display a message preventing your

	access or letting you through to the next program that starts your user session.

	

<HR>



</DL>



<H4 ALIGN="CENTER"><A NAME="Heading9<FONT COLOR="#000077">Why You Shouldnt

Use the root Login</FONT></H4>

<P>You will have to use the <TT>root</TT> login from time to time. Some things simply

cannot be done on the Linux system without logging in as <TT>root</TT>. You should

not, however, use the <TT>root</TT> login as your regular login. This is especially

true if you are exploring the system, poking around, and trying out new commands

that may not do what you thought they would!</P>

<P>Linux, as you already know, is a multiuser, multitasking operating system. Multiuser

means that several people can be using Linux at the same time (of course, you have

to add some additional terminals to your system, or it will get very crowded around

the keyboard). Multitasking means that Linux can do more than one thing at a time.

For example, you can spell-check a document while downloading information from some

remote system. (Multiuser implies multitasking, because all users must be able to

do their own work at the same time.) Linux, therefore, is very good at juggling all

these tasks, keeping them from interfering with each other, and providing safeguards

so that you cannot damage the system or another user's work.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading10<FONT COLOR="#000077"><B>WARNING:</B> </FONT>The <TT>root</TT>

	login does not restrict you in any way. With one simple command, issued either on

	purpose or by accident, you can destroy your entire Linux installation. For this

	reason, use the <TT>root</TT> login only when necessary. Avoid experimenting with

	commands when you do log in as <TT>root</TT>. 

<HR>



</DL>



<P>When you log in as <TT>root</TT>, you become the system. The <TT>root</TT> login

is also sometimes called the superuser login, and with good reason. To use an analogy,

instead of being a passenger on an airplane, you suddenly have all the privileges

of the flight crew, the mechanics, and the cabin crew. &quot;Hmm, what does this

do?&quot; becomes an extremely dangerous phrase when logged in as <TT>root</TT>.</P>

<P>One of the oldest stories in UNIX lore tells of new users who log in as <TT>root</TT>

and, in 10 keystrokes, destroy their system completely and irrevocably. But if you're

careful to follow the steps given here, and stop and take a moment to think about

the commands you are giving, none of the &quot;How many new users does it take to

nuke a system?&quot; jokes will apply to you!



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading11<FONT COLOR="#000077"><B>NOTE: </B></FONT>System administrator

	is another term you will see often. A system administrator is the actual person who