CHAPTER 1- INTRODUCTION TO LINUX 1.1 WHAT’S UNIX UNIX is an operating system which was first developed in the 1960s. A product of the 1960s, UNIX and its related software was invented by Dennis Ritchie, Ken Thompson, Brian Kernighan, and other hackers at Bell Labs in 1969. UNIX is a computer operating system, a control program that works with users to run programs, manage resources, and communicate with other computer systems. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops. UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. The UNIX operating system is made up of three parts; the kernel, the shell and the programs. 1.2 WHAT’S LINUX A famous professor Andrew Tanenbaum developed Minix, a simplified version of UNIX that runs on PC.Minix is for class teaching only. No intention for commercial use.In Sept 1991, Linus Torvalds, a second year student of Computer Science at the University of Helsinki, developed the preliminary kernel of Linux, known as Linux version 0.0.1.It was licensed under GNU General Public License, thus ensuring that the source codes will be free for all to copy, study and to change. Linux has been used for many computing platforms like PC, PDA, Supercomputer,… etc.Not only character user interface, graphical user interface is also available. 1.3 WHAT’S OPEN SOURCE The term "open source" refers to something that can be modified because its design is publicly accessible.Open Source is a type of software distribution that allows the user access to the program's source code, to view the source code, modify it, and redistribute it to others.Open source software is software whose source code is available for modification or enhancement by anyone. CHAPTER 2- WHAT EVERY LINUX USER KNOWS This chapter concerns those concepts and commands that every Linux user knows−−how to start and stop the system, log in and out from it, change your password, see what is happening on the system, and use the system help facilities. 2.1 CONTROLLING POWER TO THE SYSTEM How to start and stop power to the system−−how to turn it on and turn it off. It's more than just pressing the button on the case; in particular, there is a right way to turn off the system, and doing it wrong can result in losing some of your work. 2.1.1 Powering Up the System The first thing you do to begin using the system is start power to it. To power up the system, just turn it on. This is called booting the system. As the Linux kernel boots there will be many messages on the screen. After a while, the system will display a login: prompt. You can now log in. Some systems are configured to start xdm at boot time. If your system is configured like this, instead of the login: prompt described above, you'll see a graphical screen with a box in the middle containing both login: and Password: prompts. Type CTRL−ALT−F1 to switch to the first virtual console, where you can log in to the system in the usual way. 2.1.2 Turning Off the System You can't just flip the power switch when you are done using the computer, because Linux is constantly writing data to disk. (It also keeps data in memory, even when it may have appeared to have written that data to disk.) Simply turning off the power could result in the loss or corruption of some of your work. To turn off a single user system, first log out of all consoles. Then, type CTRL−ALT−DEL (press and hold these three keys at once). The system will print some messages as it shuts down, and when you see the line, ‘Rebooting...', it's safe to turn the power to machine off. 2.2 ACCOUNTS AND PRIVILEGES Linux is a multi−user system, meaning that many users can use one Linux system simultaneously, from different terminals. So to avoid confusion (and to maintain a semblance of privacy), each user's workspace must be kept separate from the others. Even if a particular Linux system is a stand−alone personal computer with no other terminals physically connected to it, it can be shared by different people at different times, making the separation of user workspace still a valid issue. This separation is accomplished by giving each individual user an account on the system. Unique username that identifies you to the system and to other users. It is the name that the system will then forever know you as; it's a single word, in all lowercase letters. During the installation process, the system administrator should have created an account for you. (The system administrator has a special account whose username is root; this account has total access to the entire system, so it is often called the superuser.) In addition to your username, you should also have a password that you can keep secret so that only you can use your account. 2.2.1 Logging In to the System To begin a session on a Linux system, you need to log in. Do this by entering your username at the login: prompt on your terminal, and then entering your password when asked. The login: prompt appears on the terminal after the system boots. If your system is configured to start the X Window System at boot time, you'll be presented with an X login screen instead of the standard login prompt. If that happens, press CTRL−ALT−F1 to switch to the text login screen. A typical login: prompt looks like this: Debian GNU/Linux 2.2 bardo tty1 bardo login: Every Linux system has its own name, called the system's hostname; a Linux system is sometimes called a host, and it identifies itself with its hostname at the login: prompt. It's important to name your system−−like a username for a user account, a hostname gives name to the system you are using. The system administrator usually names the system when it is being initially configured. Like usernames, hostnames are one word in all lowercase letters.. In this example, `bardo' is the hostname of this particular Linux system. The name of the terminal you are connecting from is displayed just after the hostname. In this example, the terminal is `tty1', which means that this is the first terminal on this particular system. To log in to the system, type your username (followed by RET) at the login: prompt, and then type your password when asked (also followed by RET); for security purposes, your password is not displayed on the screen when you type it. To log in to the system with a username of `kurt' and a password of `empathy', type: Debian GNU/Linux 2.2 bardo tty1 bardo login: kurt RET Password: empathy RET Linux bardo 2.0.30 #1 Tue Jul 29 10:01:26 EDT 1997 i586 unknown Copyright (C) 1993−1998 Software in the Public Interest, and others Most of the programs included with the Debian Linux system are freely redistributable; the exact distribution terms for each program are described in the individual files in /usr/doc/*/copyright Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. Last login: Tue Apr 5 12:03:47 on tty1. No mail. ~ $ Once you've entered your username and password, you are "logged in" to the system. You can then use the system and run commands. The system then displays the time and date of your last login, and reports whether or not you have electronic mail waiting for you . Finally, the system puts you in a shell−−−the environment in which you interact with the system and give it commands. Use of the default shell on most Linux systems, bash. The dollar sign (`$') displayed to the left of the cursor is called the shell prompt; it means that the system is ready and waiting for input. 2.2.2 Logging Out of the System To end your session on the system, type logout at the shell prompt. This command logs you out of the system, and a new login: prompt appears on your terminal. To log out of the system, type: $ logout RET Debian GNU/Linux 2.2 bardo tty1 bardo login: What works equally well to typing the logout command is to just type C−d (hold down CTRL and press D). You don't even have to type RET afterwards. 2.3 CONSOLE BASICS A Linux terminal is a place to put input and get output from the system, and usually has at least a keyboard and monitor. When you access a Linux system by the keyboard and monitor that are directly connected to it, you are said to be using the console terminal. Linux systems feature virtual consoles, which act as separate console displays that can run separate login sessions, but are accessed from the same physical console terminal. Linux systems are configured to have seven virtual consoles by default. When you are at the console terminal, you can switch between virtual consoles at any time, and you can log in and use the system from several virtual consoles at once. 2.3.1 Switching between Consoles To switch to a different virtual console, press ALT−Fn, where n is the number of the console to switch to.To switch to the fourth virtual console, press ALT−F4.This command switches to the fourth virtual console, denoted by `tty4': Debian GNU/Linux 2.2 bardo tty4 bardo login: You can also cycle through the different virtual consoles with the left and right arrow keys.