Chapter 4. Basic Unix
Commands
and Concepts
If you've come to Linux from MS-DOS or another
non-Unix operating system, you have a steep
learning curve ahead of you. We might as well be candid on this
point. Unix is a world all its own.
In this chapter, we're going to introduce the rudiments of
Unix for those readers who have never had exposure
to this operating system. If you are coming from
MS-DOS, Microsoft Windows, or other environments,
the information in this chapter will be absolutely vital to you.
Unlike other operating systems, Unix is not at all
intuitive. Many of the commands have seemingly odd names or syntax,
the reasons for which usually date back many years to the early days
of this system. And, although many of the commands may appear to be
similar to their MS-DOS counterparts, there are
important differences.
There are dozens of other books that cover basic
Unix usage. You should be able to go to the
computer section of any chain bookstore and find at least three or
four of them on the shelf. (A few we like are listed in the Bibliography.) However, most of these books cover
Unix from the point of view of someone sitting down
at a workstation or terminal connected to a large mainframe, not
someone who is running their own Unix system on a
personal computer.
Also, these books often dwell upon the more mundane aspects of
Unix: boring text-manipulation commands, such as
awk, tr, and
sed, most of which you will never need unless you
get into doing some serious Unix trickery. In fact,
many Unix books talk about the original
ed line editor, which has long been made obsolete
by vi and Emacs. Therefore, although many of the
Unix books available today contain a great deal of
useful information, many of them contain pages upon pages of humdrum
material you couldn't probably care less about at this point.
Instead of getting into the dark mesh of text processing, shell
syntax, and other issues, in this chapter we strive to cover the basic
commands needed to get you up to speed with the system if you're
coming from a non-Unix environment. This chapter
is far from complete; a real beginner's Unix
tutorial would take an entire book. It's our hope that this chapter
will give you enough to keep you going in your adventures with Linux,
and that you'll invest in one of the aforementioned
Unix books once you have a need to do so. We'll
give you enough Unix background to make your
terminal usable, keep track of jobs, and enter essential
commands.
Chapter 5, "Essential System Management", contains material
on system administration and maintenance. This is by far the most
important chapter for anyone running his own Linux system. If you
are completely new to Unix, the material found in
Chapter 5, "Essential System Management" should be easy to follow given the
tutorial here.
One big job we don't cover in this chapter is how to edit files. It's
one of the first things you need to learn on any operating system.
The two most popular editors for Linux, vi and Emacs, are
discussed at the beginning of Chapter 9, "Editors, Text Tools,
Graphics,
and Printing".
4.1. Logging In
Let's assume that your installation went completely smoothly, and you
are facing the following prompt on your screen:
Linux login:
Many Linux users are not so lucky; they have to perform some heavy
tinkering when the system is still in a raw state or in single-user
mode. But for
now, we'll talk about logging into a functioning Linux system.
Logging in, of course, distinguishes one user from another. It lets
several people work on the same system at once and makes sure that
you are the only person to have access to your files.
You may have installed Linux at home and be thinking right now, "Big
deal. No one else shares this system with me, and I'd just as soon
not have to log in." But logging in under your personal account also
provides a certain degree of protection: your account won't have the
ability to destroy or remove important system files. The system
administration account (covered in the next chapter) is used for such
touchy matters.
If you connect your computer to the Internet, even via a modem, make sure
you set non-trivial passwords on all of your accounts.
Use punctuation and strings that don't represent real words or names.
You were probably asked to set up a login account for yourself when
you installed Linux. If you have such an account, type the name you
chose at the Linux login: prompt. If you don't have an account yet,
type root because that account is certain to exist. Some
distributions may also set up an account called install or some
other name for fooling around when you first install the system.
After you choose your account, you see:
Password:
and you need to enter the correct password. The terminal turns off
the normal echoing of characters you enter for this operation, so that nobody looking at the screen can
read your password. If the prompt does not appear, you should add a
password to protect yourself from other people's tampering; we'll go
into this later.
By the way, both the name and the password are case-sensitive. Make sure the Caps Lock key is not set, because typing ROOT
instead of root will not work.
When you have successfully logged in, you will see a prompt. If
you're root, this may be a simple:
#
For other users, the prompt is usually a dollar sign.
The prompt may also contain the name you assigned
to your system or the directory you're in currently. Whatever
appears here, you are now ready to enter commands. We say that you
are at the "shell level" here and that the prompt you see is the "shell
prompt."
This is because you are running a program called the shell that
handles your commands. Right now we can ignore the shell, but later
in this chapter we'll find that it does a number of useful things
for us.
As we show commands in this chapter, we'll show the prompt simply as
$. So if you see:
$ pwd
it means that the shell prints $ and that pwd is what
you're supposed to enter.
 |  |  | | 3.3. Running Into Trouble |  | 4.2. Setting a Password |
Copyright © 2001 O'Reilly & Associates. All rights reserved.
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