CHAP-1 INTRODUCTION TO LINUX 1 Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce

 Linux is a freely distributed implementation of a UNIX-like kernel, the lowlevel core of an operating system.  Because Linux takes the UNIX system as its inspiration, Linux and UNIX programs are very similar. In fact, almost all programs written for UNIX can be compiled and run on Linux. Also, some commercial applications sold for commercial versions of UNIX can run unchanged in binary form on Linux systems Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 2

 Linux, itself is the core of the operating system: the kernel. The kernel is the program acting as chief of operations.  It is responsible for starting and stopping other programs (such as editors), handling requests for memory, accessing disks, and managing network connections. The kernel is a nontrivial program. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 3

 The Linux community (together with others) supports the concept of free software, that is, software that is free from restrictions, subject to the GNU General Public License (the name GNU stands for the recursive GNU’s Not Unix).  Although there may be a cost involved in obtaining the software, it can thereafter be used in any way desired and is usually distributed in source form. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 4

 A few major examples of software from the GNU Project distributed are as follows:  GCC: The GNU Compiler Collection, containing the GNU C compiler  G++: A C++ compiler, included as part of GCC  GDB: A source code–level debugger  GNU make: A version of UNIX make  Bison: A parser generator compatible with UNIX yacc  bash: A command shell  GNU Emacs: A text editor and environment Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 5

 Linux distributions can be broadly categorized into two groups.  The first category includes the purely commercial distros, and the second includes the noncommercial distros, or spins.  The commercial distros generally offer support for their distribution—at a cost. The commercial distros also tend to have a longer release life cycle.  Examples of commercial flavors of Linux-based distros are RHEL, SuSE Linux Enterprise (SLE), etc.  The noncommercial distros, on the other hand, are free. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 6

 the Linux system administrator is the person who has “root”access, which is to say the one who is the system’s “super user” (or root user).  The “root” user has unfettered access to everything all user accounts, their home directories, and the files therein; all system configurations; and all files on the system.  System administrator has full system privileges,  No one should ever log in as “root,” because system administration tasks can be performed more easily and safely through other, more specific means.  Compare to it a standard Linux user is limited as to the things he or she can do with the underlying engine of the system. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 7

 Linux server runs even on a standalone machine with one user account. It must be configured.  Linux is a multiuser operating system. Each user has (or shares) an account on the system, be it on a separate machine or on a single machine with multiple accounts.  One reason that these concepts are crucial is found in the administration of application software — productivity programs.  While it is possible for individual users to install some applications in their home directories — drive space set aside for their own files and customizations — these applications are not available to other users without the intervention of the system administrator.  Besides, if an application is to be used by more than one user, it probably needs to be installed higher up in the Linux file hierarchy, which is a job that can be performed by the system administrator only. (The administrator can even decide which users may use which applications by creating a “group” for that application and enrolling individual users into that group.) Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 8

 No one can show up and log on to a Linux machine.  The system administrator can only create an account for every user and gives permission for respective tasks such as accessing files, editing of files etc.  A system administrator can access all accounts as it login as root and can performs some administrative tasks which include creating and manipulating user accounts ( add, modify, delee or copy user accounts), change password whenever it requires, defining group of related users which can share access to a file or directory and providing access to connect to server.  Administrator is responsible for maintaining security by providing role on a user account that defines a level of access. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 9

 there is a need to back up important files so that in the event of a failure of hardware, security, or administration, the system can be up and running again with minimal disruption. Only the system administrator may do this. (Because of its built-in security features, Linux may not allow users to be able even to back up their own files to floppy disks.) Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 10

 To minimize the disruption of data, administrator maintains backups of files, to restore them whenever required.  Baking up files is one of the most critical tasks in system administration.  Administrator maintains proper and regular back ups to prevent damage to data. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 11

 It is a essential parts of administration to keep linux working more efficiently.  Sysem tuning is an unending practice supported by a variety of diagnostics and monitoring tools.  To get good idea of how a system is performing, CPU, memory, I/O, and network needs to be monitored.  For maintaing efficient performance tuning it requires to understand how various computer modules communicate. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 12

 It is a most important task of administration. For this excellent task and decision requires to run a secure linux sysem and maintaining data integrity.  Administrator makes sure that a user or program can perform only those actions that they are allowed to perform. For this administrator must 1) Make sure that system has firewalls 2) Not allow connections from unknown networks, if possible. 3) Block all unnecessary services on linux system. 4) Only that software have to be loaded which is must require, otherwise do not install useless software. 5) Must configure network, system application and services to maintain secuirty and should be aware of the tools which can be used to monitor hacker threats. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 13

 The term mount point refers to the directory you associate with a disk partition or any other device.  Suppose that you have two disks on your PC, and you have created Linux partitions  on both disks. Figure below illustrates how you can mount different parts of the Linux directory tree (the file system) on these two partitions. Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 14

Created By: Asst. Prof. Ashish Shah, J.M.Patel College of Commerce 15