Linux is an open-source operating system based on the Unix model. It can run on a variety of hardware and has thousands of available programs. The document discusses the history and development of Linux from its origins in the 1960s through its creation by Linus Torvalds in 1991. It also covers key Linux concepts like kernels, processes, threads, file systems, and boot processes. Community links are provided for learning more about the Linux kernel, drivers, boot loader, and file systems.

1. Introduction To Linux
Suresh Kalidasan

2. What is Linux
 A Unix-like Operating System
 A famous open source project
 Free to use, distribute, modify under a compatible licence
 Produced by a large developer and user community
 A combination of many projects
 Cost of commercial development estimated at USD 7 billion
 Companies often make money by selling:
 Support
 Training
 Custom changes

3. How Linux can help us ?
 Full operating system
 Works well on a variety of hardware, including older
hardware
 You can adapt it to fit your needs
 Thousands of programs available
 Secure by design
 LAMP stack
 Supports a wide range of programming languages
 Scalable

4. History
 1965 - Bell Labs (AT&T), GE and MIT, Project to develop a new (multiuser, multitasking) operating
system - MULTICS. (not successful)
 1969 - Ken Thompson and Dennis Ritchie implemented the first UNIX system for the PDP-7.
 1973 - The UNIX system was rewritten in the C programming language.
 1982 - University of California, Berkeley (UCB), Developed BSD UNIX because new commercial
UNIX releases no longer included the source code.
 1984 - Richard Stallman started the GNU project to create a free operating system.
 1991 they created a lot of the tools but no kernel.
 Professor Andrew Tanenbaum wrote the operating system MINIX from scratch to teach his students
the inner workings of a real operating system.
 1991 Apr - At age 21, Linus Torvalds starts working on a new operating system inspired by MINIX.
 1991 September - Linux version 0.01 is released.

5. Linux Application

6. Some Linux Flavors
http://en.wikipedia.org/wiki/List_of_Linux_distributions

7. Linux vs Windows
Linux Windows
Linux was originally built by Linus Torvalds at Firstversion of Windows – Windows 3.1
the University of Helsinki in 1991. released in 1992 by Microsoft.
Linux is a Unix-like, Kernel-based, fully Windows is a GUI based operating system
memory-protected, multitasking operating It has powerful networking capabilities, is
system multitasking, and extremely user friendly
It runs on a wide range of hardware from PCs Many beginner users find Windows easer to
to Macs. use than other operating systems
Linux has been primary used by advanced Windows is often known for a large amount of
computer users – programmers and developers loop holes
Linux is more virus proof since viruses – User Interface is well known for Windows
malicious programs either cannot be run
automatically on the Linux machine, or simply
are not capable of being executed on a 386
architecture
User Interface in latest flavors like Ubuntu is
comparatively equal

8. User Space vs Kernel Space
User Space Kernel Space
User space is the  Kernel Space us
memory area where all strictly reserved for
user mode application running the kernel (OS
work and this memory background process),
can be swapped out kernel extensions and
when necessary most device drivers
User space process Linux kernel space
normally runs in its gives full access to the
own virtual memory hardware, although
space and unless some exceptions runs
explicitly requested, in user space. (The
cannot access the graphic system most
memory of other people use with Linux
processes. does not run in kernel
in contrast to that
found in Microsoft
Windows)

9. Kernel Types

10. What is a process ?
 Actual execution of passive collection of
instructions
 Eg:
 Running Adobe acrobat reader
 Running word pad
 Running Printer application
 All the above are named as process in OS
and this can be run parallel, methodology
named as Multi-Tasking

11. What is Thread ?
 In Linux threads are initiated
and executed inside a process
(process specific area)
 Multiple threads can exist within
the same process and share
resource such as memory, while
different process do not share
these resource
 Eg: opening multiple instance
of .pdf extension files in a adobe
acrobat reader

12. Process/Threads state Diagram
 Process gets
initiated from
Creation state and
ended with
terminated state,
depending on the
logic of program
other states are
valid

13. Boot Flow diagram
 GRUB ( Grand Unified
Bootloader) is Multi-boot
boot loader
 A Master Boot Record is a
512 bye boot sector that
is the first sector of a
partitioned data storage
such as hard disk
 Root filesystem is the file
system that is contained
on the same partition on
which the root directory is
located.

14. Simplified Linux Kernel Diagram

15. Kernel map and connection flow

16. File system architecture

17. Detailed File system structure

18. Anatomy of Linux

19. Open Community Links
 Linux kernel availability
 http://www.kernel.org/
 http://www.linux.org/
 Linux Drivers
 http://www.linux-drivers.org/
 Grub
 http://www.gnu.org/software/grub/index.html
 File System
 http://www.busybox.net/
 Google will be your best friend

20. This Document Release date
S.No Author Release Description
Version/Date
1 Suresh v0.1 / 08 Dec 2010 Initial Version
Kalidasan