Linux Introduction And Basic Linux Concepts
If you're new to UNIX and Linux, you may be a bit intimidated by the size and apparent complexity of the system before you. This chapter does not go into great detail or cover advanced topics. Instead, we want you to hit the ground running.
We assume very little here about your background, except perhaps that you have some familiarity with personal computer systems, and MS-DOS. However, even if you're not an MS-DOS user, you should be able to understand everything here. At first glance, Linux looks a lot like MS-DOS--after all, parts of MS-DOS were modeled on the CP/M operating system, which in turn was modeled on UNIX. However, only the most superficial features of Linux resemble MS-DOS. Even if you're completely new to the PC world, this tutorial should help.
And, before we begin: Don't be afraid to experiment. The system won't bite you. You can't destroy anything by working on the system. Linux has built-in security features to prevent ``normal'' users from damaging files that are essential to the system. Even so, the worst thing that can happen is that you may delete some or all of your files and you'll have to re-install the system. So, at this point, you have nothing to lose.
Linux is a multitasking, multiuser operating system, which means that many people can run many different applications on one computer at the same time. This differs from MS-DOS, where only one person can use the system at any one time. Under Linux, to identify yourself to the system, you must log in, which entails entering your login name (the name the system uses to identify you), and entering your password, which is your personal key for logging in to your account. Because only you know your password, no one else can log in to the system under your user name.
On traditional UNIX systems, the system administrator assigns you a user name and an initial password when you are given an account on the system. However, because in Linux tt you are the system administrator, you must set up your own account before you can log in. For the following discussions, we'll use the imaginary user name, ``larry.''
In addition, each system has a host name assigned to it. It is this host name that gives your machine a name, gives it character and charm. The host name is used to identify individual machines on a network, but even if your machine isn't networked, it should have a host name. For our examples below, the system's host name is ``mousehouse''.
3.2.1 Creating an account.
Before you can use a newly installed Linux system, you must set up a user account for yourself. It's usually not a good idea to use the root account for normal use; you should reserve the root account for running privileged commands and for maintaining the system as discussed below.
In order to create an account for yourself, log in as root and use the useradd or adduser command. See Section 4.6 for information on this procedure.
3.2.2 Logging in.
At login time, you'll see a prompt resembling the following:
tscreen2360
Enter your user name and press the Enter key. Our hero, larry, would type:
tscreen2364
Next, enter your password. The characters you enter won't be echoed to the screen, so type carefully. If you mistype your password, you'll see the message
tscreen2366
and you'll have to try again.
Once you have correctly entered the user name and password, you are officially logged in to the system, and are free to roam.
3.2.3 Virtual consoles.
The system's console is the monitor and keyboard connected directly to the system. (Because Linux is a multiuser operating system, you may have other terminals connected to serial ports on your system, but these would not be the console.) Linux, like some other versions of UNIX, provides access to virtual consoles (or VCs), that let you have more than one login session on the console at one time.
To demonstrate this, log in to your system. Next, press Alt-F2. You should see the login: prompt again. You're looking at the second virtual console. To switch back to the first VC, press Alt-F1. Voila! You're back to your first login session.
A newly-installed Linux system probably lets you to access only the first half-dozen or so VCs, by pressing Alt-F1 through Alt-F4, or however many VCs are configured on your system. It is possible to enable up to 12 VCs--one for each function key on your keyboard. As you can see, use of VCs can be very powerful because you can work in several different sessions at the same time.
While the use of VCs is somewhat limiting (after all, you can look at only one VC at a time), it should give you a feel for the multiuser capabilities of Linux. While you're working on the first VC, you can switch over to the second VC and work on something else.
3.2.4 Logging out.
Before we delve much further, we should tell you how to log out of the system. At the shell prompt, use the command
tscreen2419
to log out.
