Hi,
Welcome to Linux World
-Manoj Kumar
Operating System?
 What is Operating System?
 Operating System is an Interface between User and the Computer-Hardware.
 The Hardware of the computer cannot understand the human readable language, as it works on binaries -> i.e. 0’s
and 1’s.
 Also it is very tough for humans to understand the binary language.
 In above cases we need an Interface which can translate human language to hardware and vice-versa for
effective communication.
Types of Operating Systems!
 Single User – Single Task Operating System
In this type of O/S supports only one user can log into system and can perform only one task at a time.
Ex: MS-DOS
 Single User – Multi Tasking Operating System
In this type of O/S supports only one user can log into system but a user can perform multiple tasks at a
time, chatting in Facebook while playing songs etc.
Ex: Windows, XP..
 Multi User – Multi Tasking Operating System
In this type of O/S provides multiple users to log into the system and also each user can perform
vicarious tasks at a time. In a broader term multiple users can logged in to system and share the
resources of the system at the same time
Ex: UINX, LINUX..
Introduction of Linux
 History of UNIX
 Linux Origins
 Architecture of Linux
 What is Kernel?
 What is Shell?
 File System Hierarchy in Linux
 Why Linux?
 Booting Procedure
 History of UNIX
 Before development of UNIX operating system at AT & T Bell labs, Software team lead by Ken Thomson, Dennis
Ritchie and Rudd Canday worked on MULTICS project.
 MULTICS stands for “Multi Information Computing System”.
 The aim of this project is to share the same data by ‘n’ number of users at the same time.
 Initially, MULTICS was developed for only two users.
 Based on the same concept in 1969, UNICS operating system was developed for 100’s of users.
 UNICS stands for “Uniplexed Information Computing System”.
 Initially UNICS was written in Assembly Language.
 In 1973, they rewritten in ‘C’ Language named as UNIX.
 Linux Origins
LINUS TORVALDS
Created Linux Kernel
When Linux Kernel combined with GNU applications, complete free UNIX like OS(LINUX) was developed.
GNU Project/ FSF
GNU project started in 1984
FSF - Free Software Foundation ( Non-Profit organization that manages the GNU project )
Goal: Create ‘free’ UNIX clone
GPL (General Public License)
primary license for open source software
encourages free software
 What is Kernel?
kernel is a
of an operating system.
It is low level & easily replaceable program or software.
It acts as an interface between the user applications and the hardware in your computer.
The aim of the kernel is to manage the communication between the software (user level applications) and
the hardware (CPU, disk memory etc).
The main tasks of the kernel are :
Process management
Device management
Memory management
Interrupt handling
I/O communication
File system...etc..
Types: monolithic, microkernel, and hybrid.
 What is Shell?
Computer understand the language of 0's and 1's called binary language, which is difficult for all of us, to read
and write. so in Os there is special program called Shell.
Shell provides the user interface or interaction.
So, shell is a command language interpreter, it reads the commands from the standard input device (keyboard) in
human readable language and pass to kernel for execution.
Shell is not part of system kernel, but uses the system kernel to execute programs, create files etc.
Types:
BASH ( Bourne-Again-Shell ) - Most common shell in Linux. It's Open Source.
CSH ( C-Shell ) - The C shell's syntax and usage are very similar to the C programming language.
KSH ( Korn Shell ) – Created by David Korn at AT &T Bell Labs.
TCSH - It is an enhanced but completely compatible version of the Berkeley UNIX C-shell (CSH)
# echo $SHELL
 Architecture of Linux
USER APP
CLI
SEQUENCING
HARDWARE
SCHEDULER
MEMORY
RAW DATA
 Architecture of Linux
USER
SHELL
KERNEL
HARDWARE
 Why Linux?
 Multi User Capability
 Multi Tasking Capability
 Programming Facility
 Portability
 Without Virus
 Communication (Electronic Mail)
 Open System
 Help Facility [ # man command = # man cat or # man man and # command --help = # whoami - - help ]
 Security
Firewall or Iptables
SELINUX
Special Permissions
(SUID,SGID,
STICKYBIT,ACL)
Security
Basic File Permissions
BIOS
MBR
GRUB
Basic Input / Output System – Executes MBR
Master Boot Record – Executes GRUB
Grand Unified Boot Loader - Execute Kernel
POST
KERNEL
Kernel – Executes /sbin/init
INIT
TARGETS
INIT – Executes Run level Programs
RUN LEVEL
PROGRAMS
Run level Programs are executed from /etc/rc.d/rc*.d/
Booting Sequence
 File System Hierarchy in Linux
Course Contents
‘’Asking stupid question is better than the before doing
Stupid mistake’’
Thank you for spending your valuable time
and
Have a good day 