Linux is a Unix-like and mostly POSIX-compliant computer operating system (OS) assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on 5 October 1991 by Linus Torvalds. The Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy. The primary difference between Linux and many other popular contemporary operating systems is that the Linux kernel and other components are free and open-source software. Linux is not the only such operating system, although it is by far the most widely used. Some free and open-source software licenses are based on the principle of copyleft, a kind of reciprocity: any work derived from a copyleft piece of software must also be copyleft itself. The most common free software license, the GNU General Public License (GPL), is a form of copyleft, and is used for the Linux kernel and many of the components from the GNU Project. Tux the penguin, mascot of Linux Developer: Community Written in: Primarily C and assembly OS family: Unix-like Working state: Current Source model: Mainly open source, proprietary software also available Initial release: 1991; 24 years ago Marketing target: Personal computers, mobile devices, embedded devices, servers, mainframes, supercomputers Available in: Multilingual Platforms: Alpha, ARC, ARM, AVR32, Blackfin, C6x, ETRAX CRIS, FR-V, H8/300, Hexagon, Itanium, M32R, m68k, META, Microblaze, MIPS, MN103, Nios II, OpenRISC, PA-RISC, PowerPC, s390, S+core, SuperH, SPARC, TILE64, Unicore32, x86, Xtensa Kernel type Monolithic (Linux kernel) Userland: Various Default user interface: Many License: GPL version 2 and other free and open-source licenses, except for the "Linux" trademark.

1. INTRODUCTION TO LINUX

2. Overview of LINUX system
 Two parts – Kernel and Shell
 Kernel
 Core part of the operating system and communicates directly
with the hardware.
 User programs access the kernel through a set of functions
called system calls.
 Shell
 It is a command interpreter.
 Acts as an interface between user and kernel.


3. Kernel-Shell Relationship

4. Characteristics
 Multiuser and Multiprocess
 File and Process
 Data, directory, process, hard disk etc (almost everything) are
expressed as a file.
 Process is a running program identified by a unique id (PID)

5. Directory Structure
 Files are put in a directory.
 All directories are in a hierarchical structure (tree structure).
 User can include or remove any directories on the tree.
 Top directory is “/”, which is called slash or root.
 Users have their own directory (home directory).

6. Directory Structure

7. Linux Overview
 Normal User and Super user
 In linux, administrator, is a special user which has all the rights.
 This special user is called root or superuser.
 Case Sensitive
 Myfile.doc and MYFile are different.

8. Basic Commands
 One command consists of 3 parts
 Command name
 Options
 Arguments
 Example:
[Ubuntu@ubuntu`]$ command-name optionA option arg1 arg2
 A space is necessary between command name, options and arguments.
 cd ..
 ls –l
 mv file1 file2

9. Relative and Absolute Path
 Path means a position in the directory tree.
 To express a path, you can use relative path or absolute path.
 In relative path expression, the path is not defined uniquely, it depends on
your current path.
 In absolute path expression, the path is defined uniquely, it does not
depend on the current path.

10. Relative and Absolute Path
 Absolute path starts with “/”
 Eg: cd /home/user1/home/a.out
 There are two special characters in the current path
 . For current directory
 .. For parent directory

11. Redirect and Append
 Output of a command is displayed on screen.
 Using “>” you can redirect the output from screen to a file.
 Using “>>” you can append the output to the bottom of the file.

12. Pipe
 Some commands require input from a file or other commands.
 Using “|”, you can use output from other command as input to the
command.

13. Basic Commands
 man <command> – shows all information about the command.
 Eg: man ls
 <command> --help – shows the available options for that command.
 Eg: ls -- help
 mkdir – creates a directory
 Eg: mkdir dir1
 rmdir – removes a directory
 Eg: rmdir dir1

14. Basic Commands
 cd –change directory
 To change to a particular directory: cd <directory name>
 Eg: cd dir1
 cd .. Moves you one directory up.

15. Basic Commands
 echo – writes a message to your screen.
 Eg: echo hello
 pwd – print name of current working directory.
 Eg: pwd
 who – to know the users who are currently working.
 Eg: who
 date – shows date and time
 Eg: date

16. Basic Commands
cal – to see the calendar of any specific month
 Usage: cal month year
 Eg: cal 7 2012 displays july’s calendar of 2012
 cp – to copy file or directory
 Eg: cp file1 file2
 ls – obtains a list of all commands in the current directory
 Eg: ls

17. Thank You