This document provides an overview of the Linux operating system, including: - Linux is an open-source operating system that functions similarly to Windows and OS X by relaying instructions between applications and computer components. - It has grown significantly since its creation in 1991 and now powers a wide range of devices from phones to supercomputers. - As an open-source project, Linux is developed and supported collaboratively by thousands of individual and corporate developers worldwide.

1. What is Linux
Linux is, in simplest terms, an operating system. It is the software on a
computer that enables applications and the computer operator to access the
devices on the computer to perform desired functions. The operating system
(OS) relays instructions from an application to, for instance, the computer's
processor. The processor performs the instructed task, then sends the results
back to the application via the operating system.
Explained in these terms, Linux is very similar to other operating systems,
such as Windows and OS X.
But something sets Linux apart from these operating systems. The Linux
operating system represented a $25 billion ecosystem in 2008. Since its
inception in 1991, Linux has grown to become a force in computing, powering
everything from the New York Stock Exchange to mobile phones to
supercomputers to consumer devices.
As an open operating system, Linux is developed collaboratively, meaning no
one company is solely responsible for its development or ongoing support.
Companies participating in the Linux economy share research and
development costs with their partners and competitors. This spreading of
development burden amongst individuals and companies has resulted in a
large and efficient ecosystem and unheralded software innovation.
Over 1,000 developers, from at least 100 different companies, contribute to
every kernel release. In the past two years alone, over 3,200 developers from
200 companies have contributed to the kernel--which is just one small piece of
a Linux distribution.
This article will explore the various components of the Linux operating
system, how they are created and work together, the communities of Linux,
and Linux's incredible impact on the IT ecosystem.
Where is Linux?
One of the most noted properties of Linux is where it can be used. Windows
and OS X are predominantly found on personal computing devices such as
desktop and laptop computers. Other operating systems, such as Symbian, are
found on small devices such as phones and PDAs, while mainframes and

2. supercomputers found in major academic and corporate labs use specialized
operating systems such as AS/400 and the Cray OS.
Linux, which began its existence as a server OS and Has become useful as a
desktop OS, can also be used on all of these devices. “From wristwatches to
supercomputers,” is the popular description of Linux' capabilities.
The Future of Linux
Linux is already successful on many different kinds of devices, but there are
also many technological areas where Linux is moving towards, even as
desktop and server development continues to grow faster than any other
operating system today.
Linux is being installed on the system BIOS of laptop and notebook
computers, which will enable users to turn their devices on in a matter of
seconds, bringing up a streamlined Linux environment. This environment will
have Internet connectivity tools such as a web browser and an e-mail client,
allowing users to work on the Internet without having to boot all the way into
their device's primary operating system--even if that operating system is
Windows.
At the same time, Linux is showing up on mobile Internet devices (MIDs).
This includes embedded devices such as smart phones and PDAs, as well as
net book devices--small laptop-type machines that feature the core
functionality of their larger counterparts in a smaller, more energy-efficient
package.
The growth of cloud computing is a natural fit for Linux, which already runs
many of the Internet's web servers. Linux enables cloud services such as
Amazon's A3 to work with superior capability to deliver online applications
and information to users.
Related to Linux' growth in cloud computing is the well-known success of
Linux on supercomputers, both in the high-performance computing (HPC)
and high-availability (HA) areas, where academic research in physics and
bioengineering, and firms in the financial and energy industries need reliable
and scalable computing power to accomplish their goals.
Many of the popular Web 2.0 services on the Internet, such as Twitter, Linked
In, YouTube, and Google all rely on Linux as their operating system. As new
web services arrive in the future, Linux will increasingly be the platform that
drives these new technologies.

3. The Birth of Linux
On August 25, 1991, a Finn computer science student named Linus Torvalds
made the following announcement to the Usenet group comp.os.minux:
"I'm doing a (free) operating system (just a hobby, won't be big and
professional like gnu) for 386(486) AT clones. This has been brewing since
april, and is starting to get ready. I'd like any feedback on things people
like/dislike in minix, as my OS resembles it somewhat (same physical layout of
the file-system (due to practical reasons) (among other things)."
The “Minix” Torvalds referred to is a variant of the UNIX operating system,
used as a guideline for his the free operating system he wanted to run on the
x86-based consumer PCs of the day. “gnu” refers to the set of GNU (GNU Is
Not Unix) tools first put together by Richard Stallman in 1983. UNIX, the
operating system that started it all, had its origins in the old Bell Labs back in
the early 60s.
Torvalds built the core of the Linux operating system, known as the kernel. A
kernel alone does not make an operating system, but Stallman's GNU tools
were from a project to create an operating system as well--a project that was
missing a kernel to make Stallman's operating system complete. Torvalds'
matching of GNU tools with the Linux kernel marked the beginning of the
Linux operating system as it is known today.
Linux is in many ways still only at the beginning of its potential, even though
it has enjoyed tremendous success since Torvalds' first request for help in
1991.
Linux has gained strong popularity amongst UNIX developers, who like it for
its portability to many platforms, its similarity to UNIX, and its free software
license. Around the turn of the century, several commercial developers began
to distribute Linux, including VA Linux, TurboLinux, Mandrakelinux, Red
Hat, and SuSE GMbH. IBM's 2000 decision to invest $2 billion in Linux
development and sales was a significant positive event to the growth of Linux.
Today, Linux is a multi-billion dollar industry, with companies and
governments around the world taking advantage of the operating system's
security and flexibility. Thousands of companies use Linux for day-to-day use,
attracted by the lower licensing and support costs. Governments around the
world are deploying Linux to save money and time, with some governments
commissioning their own versions of Linux.

4. The analyst group IDC has projected Linux will be a $49 billion business by
2011, and there are many indications in the market that this figure will be
achieved.
The Code
Linux is also unique from other operating systems in that it has no single
owner. Torvalds still manages the development of the Linux kernel, but
commercial and private developers contribute other software to make the
whole Linux operating system.
LINUX COMMANDS
Login :-
When we start linux then we have to enter login and password
Login:- root
Password :- 12345678
Mkdir :- this command is used to make directory for store data, files, text ,etc.
Syntax :- Mkdir directory name

5. Pwd :-this command is used to know the Present Working Directory used by
user
 It is used to check location.
 Pwd is root
Rmdir:-this command is used for Removing a Directory from the database
 It is used to remove the existing directory
 MV:- sometime we want to change our directory name due o some reason
then MV command is used. This command help us to rename directory
Syntax:-
 Mv oldname new_name
 CD (Change Directory ):- in dtatbase we make many directories for the work
,sometime we have to move to one directory to another then this command is
used to change directory without exit another one

6.  This command is used to enter inter in child directory
Ls (List directory content)
 List information about the files(current directory by default) sort entries
alphabetically
Ls-r:- This command is used to display files and directories in reverse order.
 LS –s :- This command is used to flag lists file size.

7. Ls –c:- This command is used to d
 LS –a :- This command is used to List all files including hidden file starting
with ‘.‘.

8. Ls –R:- This command is used to list very long listing directory trees.
 ls -A:- This command is used to d
 Ls -L :- This command is used to shows file or directory, size, modified date
and time, file or folder name and owner of file and it’s permission.

9. Ls-x:- This command is used to display the name of directories in
alphabetically
Cat:- (Concatenates)

10. cat-v:-
it use to display text files only it is used with executable files. It displays junk.
Non printable characters can be displayed using –v option.
Cat –n:- it display number line where errors are detected. If –n version is not
supported by vi pr is used.
Cat >>:-This command is used to enter the data into file
Cat –b:- This command is used to display the data without count any space

11. Cat –ns:- This command is used to display the text with space in counting
Who:-

12. Who – b:- This command is used to display the time of the last system boot.
Who –l:- This command is used to Print system login processes.
Who –m:- This command is used to print Only information about the user
and host associated with standard input (the terminal where the command
was issued). This method adheres to the POSIX standard.
Who-t:- This command is used to Print the last time the system clock was
changed, if the information is available.
Who am i:- This command is used to d

13. Who-q:- This command is used to displays all login names, and a count of all
logged-on users.
Who-u:- This command is used to Print the idle time for each user, and the
process ID.
Who:- This command is used to display the current user id
who –r:- This command is used to Print the current run level.
who –R:- This command is used to display the current user ,current date,time

14. Calendar command
Cal:- This command is used to display the calendar.
Syntax :- Cal [option]
Cal -3:- This command is used to displays prev/current/next month output
cal –m:- This command is used to displays Monday as the first day of the
week.

15. cal –j:- This command is used to displays Julian dates (days one-based,
numbered from January 1).
cal –s:- this command is used to displays Sunday as the first day of the week.
cal –y:- this command is used to displays a calendar for the
current year.

16. Other command
cp command:- cp command is used to copy the data of one file to another file
Cat command:- this command is used to enter the data into the file and copy
to another file

17. Date command:- this command s used to show the date of that day
Mkdir help:- some time we donot know some sub commands of any command
then help command is used
Mkdir version:- This command output the version details and then exit it
-m:-

18. Mkdir –m:- This command is used to set permission mode to the directory is
that read,write, etc
Mkdir –v:- their v stand for verbose
This command print a message when any new directory is created
Touch command:- this command is used to create files in any directory
Unique command:- this command is used to print the data in the file

19. CMP COMMAND
Compare two files
The cmp utility compares two files of any type and writes the results to the
standard output. By default, cmp is silent if the files are the same; if they
differ, the byte and line number at which the first difference occurred is
reported.
Syntax
cmp [-l | -s ] file1 file2 [skip1 [skip2 ] ]
Cmp –i: compare the the filles in bytes.
Cmp -l
Print the byte number (decimal) and the differing byte values (octal) for each
difference.

20. Sleep:- Sleep command is used to delay the particular process for a specified
amount of time
Syntax:-sleep 30
Kill command is used to kill the running process
 Kill -9 pi
 Ps- ef
To find signal name

21. Kill –l 7
Kill –l

22. a) Chmod number file name .extension
Ls –l file name .extension
7. MAN:- This command is used as help command .it provide
information about particular command that gives with it.
Syntax:-

23. Man another_command
Example:- ls
This command gives information about ls command.
MAN man:-
( give information about command)
WC COMMAND
print the number of bytes, words, and lines in files .

24. SYNTAX: wc [OPTION]... [FILE]...
wc –c:- print the byte counts
wc -m:- print the character counts
wc –l:-print the newline counts
 wc –L:-print the length of the longest line.
 wc –w:-print the word counts.

25. MORE
More :-
Syntax:- more -c file name
Less :-
Syntax:-less –c file name
More:-
Syntax:-more –d file name
Less:
Syntax:- less -d file name

26. More:-
Syntax:-more +3 file name
Less:-
Syntax:- less +3 file name
Less:-
Syntax:-less –e file name

27. Vi editor
Vi command:- this command is used to create file in which the user can
code the data or print any message
Syntax:- vi file name that u want to give
The output of vi:-
Vi –r
Syntax:-
Vi –r file name
The output:-