SaigonCTT SSP, 123 Truong Dinh street, District 3 HochiMinh City Vietnam Fundamentals of Linux LEU-118 Student Guide page 1 Linux Computing Environment 1 Objectives Upon completion of this module, you should be able to: • List the four main components of a computer • Describe the three main components of the Linux operating system • Identify the three most common shells in the Linux system • Distinguish between the multitasking, multiuser, and distributed processing capabilities of the Linux system Discussion – Several different components work together to make up a computer system and a networked environment. What are some of these components? Introduction to Linux The UNIX operating system was originally developed at AT&T Bell Labs in 1969. It was created as a tool set by programmers for programmers. The early source code was made available to universities all over the country. Programmers at the University of California at Berkeley made significant modifications to the original source code and called it BSD (Berkeley Software Distribution) UNIX. They sent this new version of the UNIX environment to other programmers around the country, who then added tools and code as they saw fit. Possibly the most important advance made to the software by the programmers at Berkeley was the addition of networking software which allowed the operating system to function in a local area network (LAN). Linux is a UNIX-like operting system, developed by Linus Torvalds, a student at Helsinki University in Finland, in 1991. It is a modern, flexible, mature and free operating system. Although it started life on the Intel platform, it has since been ported to many other platforms such as Amiga, DEC Alpha, Apple Power PC, Sun workstations, and others. Linux boasts many other features: • Multitasking. Linux is a true preemptive multitasking operating system. All processes run independently of each other and leave processor management to the kernel. • Symmetrical multiprocessing. Linux currently scales up to 16 processors. • Networking. Linux supports a multitude of networking protocols. • Multiuser. Linux handles multiple users at one time logged on to a machine. • Advanced memory management. Traditional UNIX systems use swapping to manage memory, where the entire memory structure of a program is written to disk when the system is running low on memory. Linux uses paging, a page 2 method that intelligently allocates memory when system memory is running low by prioritizing memory tasks. • POSIX support. POSIX defines a minimum interface for UNIX-type operating systems. Linux currently supports POSIX 1003.1. This ensures that POSIX-compliant UNIX programs will port easily to Linux. • Multiple file systems. Linux supports several different file system formats, including DOS/Windows, OS/2, and Novell formats. This makes interoperability a reality between operating systems. Main Components of a Computer The four main components of a computer are the random access memory (RAM), the central processing unit (CPU), the input/output (I/O), and the hard disk or other mass storage device. Figure 1-1 Main Components of a Computer page 3 Random Access Memory (RAM) Random access memory, located on the memory board, is the main computer memory, often referred to as primary memory. Primary memory is that part of memory where the activity of the running system takes place. When you hear, “My system has 16 Mbytes of memory,” the speaker is talking about primary memory or RAM. A software program resides on the hard disk. When it is activated, an image or copy of that program is loaded into RAM. Images in RAM remain as long as they are needed. Once these images are no longer required, they are overwritten by other images. If power is lost or the system is rebooted, images in RAM disappear. Central Processing Unit (CPU) The central processing unit is the computer logic chip that executes instructions (processes) received from the primary computer memory (RAM). These instructions are stored in binary language. Input/Output (I/O) The input/output reads input from a device (such as your keyboard) into memory, or it writes output from memory to a device. For example, the keyboard and the mouse are the primary user input devices; the monitor, printer, and tape drive are the primary output devices. Hard Disk (or Other Forms of Mass Storage) The hard disk is a magnetic storage device where information is stored. All files, including applications (utilities), are stored on a hard disk. The Linux Distributed Computing Solution The Linux computing environment is based on the UNIX operating system. Versions of the UNIX operating system run on many different computer systems – microcomputers, personal computers (PCs), and mainframes. The operating system is a set of programs that manages all computer operations. It also provides a link between the user and system resources, converting requests which come from the mouse and/or keyboard into computer operations. There are three main parts of the operating system: • Kernel • Shell • File system page 4 Kernel The kernel is the core of the Linux computing environment. It performs the following functions: 9 The kernel is an executable file that gets loaded into memory when your system boots. It is called /kernel/genunix . • Manages devices, memory, and processes • Controls the functions (transmission of information) between the system programs (utilities) and the system hardware • Manages functions such as: o Swap space – A reserved part of the disk for the kernel to use during processing o Daemons – Processes that perform particular system tasks and monitor disks and execution o File systems – A hierarchy of directories, subdirectories, and files Shell A shell is an interface between the user and the kernel. It acts as an interpreter or translator. In other words, the shell accepts commands issued by you, interprets page 5 these commands, and executes the appropriate programs. Three shells are available in the Linux environment: • Bourne shell ($) – The default shell for the Linux computing environment. The Bourne shell was developed for the AT&T System V.2 UNIX environment. This shell does not have aliasing or history capabilities. It is typically used by system administrators. • Korn shell ($) – A superset of the Bourne shell. It has many of the Bourne shell features plus added features such as aliasing and history. This is the industry standard for normal system users. • C shell (%) – A shell based on the C programming language. Like the Korn shell, it has additional features such as aliasing and history. C shell was developed by Sun’s Bill Joy for programmers, but is used with increasing frequency by normal system users. The File System The Linux computing environment file structure is a hierarchy of directories, subdirectories, and files that are grouped together for a specific purpose. • Directory – A location for other files and directories. The Linux file system, or directory structure, enables you to create files and directories accessed through a hierarchy of directories. page 6 • Subdirectory – Any directory below another directory. For example, some of the subdirectories under the root (/) directory are/usr, /etc, and /kernel. root ( / ) usr opt dev etc home var bin sbin lib user1 user2 user3 Figure 1-4 Common Linux Subdirectories The file system is integrated with the kernel to provide an organizational structure to store your data. The topmost directory is called the root directory. It is the starting point of the file-system hierarchy. The root directory (/) is required for the operating system to function and contains critical systems files (such as the kernel, called /kernel/genunix). The /usr directory contains executable commands, system administration utilities, and library routines. The /opt directory contains Linux’s unbundled software applications. The /etc directory contains system administration files. The /home directory contains the user’s home directory. Depending on how the system has been set up by the administrator, the home directories may instead be found in /export/home. The /dev directory contains files which are pointers to device names. The file system organizes data in a hierarchical structure of directories, similar to the way a filing cabinet stores information. page 7 Directories are like file drawers. Subdirectories are similar to folders. Files are like the individual pages of information contained in the folder. The Linux operating system contains many different kinds of files: • Directories • Plain ASCII (American Standard Code for Information Interchange) documents • Applications (databases, word processing programs, and spreadsheets) • Executable programs Main Capabilities of the Operating System The Linux computing environment was designed for: • Multitasking – Enables the kernel to keep track of several processes simultaneously, which allows more than one tool or application to be used at a time 9 A user can run a program (like a spreadsheet) and edit a document using a word processor at the same time. • Multiuser capability – Enables more than one user to access the same system resources • Distributed processing – Enables the use of resources across the network page 8 Main Capabilities of the Common Desktop Environment (CDE) CDE is Motif-based and users of other UNIX and personal computer (PC) desktops should be comfortable using CDE; many of the features are common to other desktop environments. The Common Desktop Environment (CDE) • Is a graphical user interface (GUI) between the user and the operating system • Provides built-in menus for users to select and run utilities and programs without using Linux environment commands • Enables users to control multiple documents or applications on the screen at the same time • Controls activities in windows using both the mouse and the Keyboard 9 The icons pictured above represent some of the major programs and tools available with CDE. CDE is discussed in greater detail in subsequent modules. Exercise: Using the Linux Computing Environment Exercise objective – This exercise helps you review the basics of the computing environment. Tasks Answer the following questions: 1. Identify the four main components of a computer. ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ page 9 2. Describe the three main functions of the kernel. __________________________________________________ __________________________________________________ __________________________________________________ 3. In the blank spaces, write one of these three terms: kernel, shell, or file system. ¾ The _________ represents the user interface, which translates requests into actions. ¾ The _________ manages and allocates resources among users. ¾ The _________ provides command interpretation. ¾ The _________ organizes and stores data in a hierarchical structure. ¾ The _________ performs memory management. ¾ The _________ components are files and directories. ¾ The _________ controls disks, tapes, printers, terminals, communication lines, and other devices. 4. In the blank spaces, write one of these three capabilities: multitasking, multiuser, or distributed processing. ¾ The _________ capability enables users to share system resources. ¾ The _________ capability is the ability to perform several processes simultaneously. ¾ The _________ capability is the ability to use resources across a network. Workshop Labs Use what you have learned so far in this course to work through the following: 1. A new UNIX environment user calls the system administrator with a problem. Yesterday, the user was working on a project when there was a power outage. When the system recovered, the work the user had done was no longer available. What happened? 2. A user is working at a Linux workstation that has no hard disk. What options might this user have for saving work that is done during the day? Exercise Summary Discussion – Take a few minutes to discuss what experiences, issues, or discoveries you had during the lab exercises. 9 Manage the discussion here based on the time allowed for this module, which was given in the “About This Course” module. If you find you do not have time to spend on discussion, then just highlight the key concepts students should have learned from the lab exercise. page 10 [...]... components of a computer Describe the three main components of the Linux operating system Identify the three most common shells in the Linux system Distinguish between the multitasking, multiuser, and distributed processing capabilities of the Linux system Think Beyond What features of the Linux UNIX environment set it apart from a typical standalone PC environment? What would some of the benefits of these... Experiences Ask students what their overall experiences with this exercise have been You might want to go over any trouble spots or especially confusing areas at this time • Interpretations Ask students to interpret what they observed during any aspects of this exercise • Conclusions Have students articulate any conclusions they reached as a result of this exercise experience • Applications Explore with students... these features be to a company? page 12 Accessing Your System 2 Objectives Upon completion of this module, you should be able to : • List the characteristics of an effective password • Change your password • Describe the function of a mouse button • Log in and log out of a system from the command line • Log in and out of a CDE session • Manipulate windows within the CDE • Invoke and use menus and menu bars... just highlight the key concepts students should have learned from the lab exercise • Experiences Ask students what their overall experiences with this exercise have been You might want to go over any trouble spots or especially confusing areas at this time • Interpretations Ask students to interpret what they observed during any aspects of this exercise • Conclusions Have students articulate any conclusions... or MENU button, is clicked or held down, a menu of choices will appear The options available on the menu will be determined by the position of the mouse pointer when button 3 was pressed Note – For the purposes of this course, you will be instructed to left or right click to perform a specific action This assumes the standard right-hand configuration of the buttons These notes will instruct you when... Before continuing on to the next module, check that you are able to accomplish or answer the following: List the characteristics of an effective password Change your password Describe the function of a mouse button Log in and log out of a system from the command line Log in and out of a CDE session Manipulate windows within the CDE Invoke and use menus and menu bars Think Beyond On a UNIX system, it is not... students articulate any conclusions they reached as a result of this exercise experience • Applications Explore with students how they might apply what they learned in this exercise to situations at their workplace Exercise Solutions page 18 3 Change the password to mypass1 $ passwd old password: new password: re-enter new password: 4 Log out of the system $exit Check Your Progress Before continuing on... workplace Exercise Solutions 1 Identify the four main components of a computer Memory, CPU, I/O, and hard disk 2 Describe the three main functions of the kernel It manages all computer operations, controls the hardware, and converts requests coming from the mouse and keyboard into computer operations 3 In the blank spaces, write one of these three terms: kernel, shell, or file system The shell represents... this instead of Programs to access a terminal window.) 2 Type the passwd command after the system prompt and press Return 3 When the prompt Enter login password: appears, type your current password and press Return 4 When the prompt New password appears, type your new password and press Return 5 When prompted, retype the new password and press Return (This is required for verification of the new password... group to which the user belongs • • Comment – Is usually the full name of the user Login directory – Is commonly referred to as the “home” directory, where users store their files Default shell – Defines which shell the user will have upon login • Password Requirements Your password protects your account from unauthorized access In the Linux computing environment, a password • • • • • Should contain at . Vietnam Fundamentals of Linux LEU-118 Student Guide page 1 Linux Computing Environment 1 Objectives Upon completion of this module,. components of a computer • Describe the three main components of the Linux operating system • Identify the three most common shells in the Linux system