Lately, I’ve been noticing stories about how to use Linux you need to know half-a-hundred Linux shell commands and the like. Ah, what century are you from? Today, if you can see a window and handle a mouse, you’re ready to use Linux.

And no, I’m not talking about how we’re all already using Linux in devices like the TiVo or the Droid smartphone and through Linux-powered Web sites like Google. I’m talking about using Linux on the desktop.

There is nothing — I repeat, nothing — that requires any special knowledge to use Linux on the desktop today. If you’ve already mastered Windows XP, you’ll have little more trouble moving to a Linux desktop like Red Hat’s Fedora 12; Novell’s openSUSE 11.2; or Canonical’s Ubuntu 9.10 than you would in switching over to Windows 7.

I’m not saying using Linux isn’t different from running Windows. It is. For example, you’ll need special software like Crossover Linux to run Windows-specific software.

The interfaces also aren’t the same — but then, Windows 7 and Vista’s interfaces aren’t the same as XP’s, and Mac OS X’s Aqua interface doesn’t look anything like the others. Besides, can any other operating system besides Linux let you set up the interface so that it duplicates XP’s look and feel? I think not!

What you don’t need to use desktop Linux is to learn dozens of obscure Linux shell (aka command line) programs to get work done. Neither do you need to know how to edit configuration files by hand to get Linux set up properly.

Sure, it can help to know how to use the Unix/Linux shell. I was writing shell (awk, sed, and grep) scripts to get work done in Unix, and later Linux, before many of you played your first game of solitaire on Windows 1.0. My point is, for ordinary, everyday use, you don’t need to know anymore about those things than you need to know how to edit Windows’ registry to run Windows.

I use desktop Linux every day, and I’m a Linux expert. Do you know how often I turn to a terminal to get to a shell to run commands? Maybe once a month, if that.

Between the two major Linux desktop interfaces, KDE and GNOME, Linux has you covered. For applications, many of the most popular applications, such as Firefox and OpenOffice, run just the same on Linux as they do on Windows. For other end-user programs, Linux programs such as Evolution for e-mail and Pidgin for IM are just as good, if not better, than their Windows equivalents. And again, you don’t need to know anything special to use them.

Installing new software on Linux isn’t any trouble either. Better still, major Linux distributors like Ubuntu are continuing to make installing Linux software easier than ever with programs like Ubuntu Software Center.

Don’t get me wrong: if you’re running a Linux server, you really need to know Linux’s technical guts. But you know what? If you’re running a Windows server, you also need to know Window’s version of the shell, the PowerShell.

No matter what desktop operating system you’re running, if you really want control over exactly what it does, you need to know how to manage its command line tools. But for day-to-day use, Linux’s graphical interfaces makes it just as easy to use as Windows or Mac OS X. Pretending that you need to be some kind of computer wizard to run Linux on the desktop today is just downright silly.

1956

A U.S. Department of Justice consent decree enjoins AT&T from “engaging … in any business other than the furnishing of common carrier communication services.”
1969

Mar. — AT&T-owned Bell Laboratories withdraws from development of Multics (Multiplexed Information and Computing Service), a pioneering but overly complicated time-sharing system. Some important principles in Multics will be carried over into Unix.

Aug. — Ken Thompson at Bell Labs writes the first version of an as-yet-unnamed operating system, in assembly language for a DEC PDP-7 minicomputer.
1970

Thompson’s operating system is named Unics, for Uniplexed Information and Computing Service and a pun on “emasculated Multics.” (The name is later mysteriously changed to Unix.)
1971

Feb. — Unix moves to the new Digital Equipment Corp. PDP-11 minicomputer.

Nov. — The first edition of the “Unix Programmer’s Manual,” written by Ken Thompson and Dennis Ritchie, is published.
1972
Dennis Ritchie develops the C programming language.
1973

Unix matures. The “pipe,” a mechanism for sharing information between two programs, which will influence operating systems for decades, is added to Unix. Unix is rewritten from assembler into C.
1974

Jan. — The University of California at Berkeley receives a copy of Unix.

July — “The UNIX Timesharing System,” by Dennis Ritchie and Ken Thompson, appears in the monthly journal of the Association for Computing Machinery (ACM). The authors call it “a general-purpose, multi-user, interactive operating system.” The article produces the first big demand for Unix.
1976

Bell Labs programmer Mike Lesk develops UUCP (Unix-to-Unix Copy Program) for network transfer of files, e-mail and Usenet content.

1977

Unix is ported to non-DEC hardware: Interdata 8/32 and IBM 360.
1978

Bill Joy, a graduate student at Berkeley, sends out copies of the first Berkeley Software Distribution (1BSD), essentially Bell Labs’ Unix V6 with some add-ons. BSD becomes a rival Unix branch to AT&T’s Unix; its variants and eventual descendents include FreeBSD, NetBSD, OpenBSD, DEC Ultrix, SunOS, NeXTstep/OpenStep and Mac OS X.
1980

4BSD, with DARPA sponsorship, becomes the first version of Unix to incorporate TCP/IP.

1982

Bill Joy co-founds Sun Microsystems to produce the Unix-based Sun workstation.
1983

AT&T releases the first version of the influential Unix System V, which will become the basis for IBM’s AIX and Hewlett Packard’s HP-UX.

Ken Thompson and Dennis Ritchie receive the ACM’s Turing Award “for their development of generic operating systems theory and specifically for the implementation of the UNIX operating system.”

Richard Stallman announces plans for the GNU (GNU’s not Unix) operating system, a Unix look-alike composed of free software.
1984

At the Winter USENIX/UniForum meeting, AT&T describes its support policy for Unix: “No advertising, no support, no bug fixes, payment in advance.”

X/Open Co., a European consortium of computer makers, is formed to standardize Unix in the X/Open Portability Guide.
1985

AT&T publishes the System V Interface Definition (SVID), an attempt to set a standard for how Unix works.
1986

Rick Rashid and colleagues at Carnegie Mellon University create the first version of Mach, a replacement kernel for BSD Unix intended to create an operating system with good portability, strong security and use in multiprocessor applications.
1987
AT&T Bell Labs and Sun Microsystems announce plans to co-develop a system that would unify the two major Unix branches.

Andrew Tanenbaum writes Minix, an open-source Unix clone for use in computer science classrooms.
1988

The “Unix Wars” are underway. In response to the AT&T/Sun partnership, rival Unix vendors including DEC, HP and IBM form the Open Software Foundation (OSF) to develop open Unix standards. AT&T and its partners then form their own standards group, Unix International.

The IEEE publishes Posix (Portable Operating System Interface for Unix), a set of standards for Unix interfaces.
1989

Unix System Labs, an AT&T Bell Labs subsidiary, releases System V Release 4 (SVR4), its collaboration with Sun that unifies System V, BSD, SunOS and Xenix.
1990

The OSF releases its SVR4 competitor, OSF/1, which is based on Mach and BSD.
1991

Sun Microsystems announces Solaris, an operating system based on SVR4.

Linux Torvalds writes Linux, an open-source OS kernel inspired by Minix.
1992

The Linux kernel is combined with GNU to create the free GNU/Linux operating system, which many refer to as simply “Linux.”
1993

AT&T sells its subsidiary Unix System Laboratories and all Unix rights to Novell. Later that year Novell transfers the Unix trademark to the X/Open group.

Microsoft introduces Windows NT, a powerful 32-bit multiprocessor operating system. Fear of NT will spur true Unix standardization efforts.
1994

NASA invents Beowulf computing based on inexpensive clusters of commodity PCs running Unix or Linux on a TCP/IP LAN.
1996

X/Open merges with Open Software Foundation to form The Open Group.
1999

U.S. President Clinton presents the National Medal of Technology to Ken Thompson and Dennis Ritchie for their work at Bell Labs.
2001

Apple releases Mac OS X, a desktop operating system based on the Mach kernel and BSD.
2002

The Open Group announces Version 3 of the Single UNIX Specification (formerly Spec 1170).

1. What is Linux?

Linux is a free Unix-type operating system for
computer devices. The operating system is what
makes the hardware work together with the software.
The OS is the interface that allows you to do
the things you want with your computer. Linux
is freely available to everyone. OS X
and Windows are other widely used
OS.

Linux gives you a graphical interface that makes
it easy to use your computer, yet it still allows
those with know-how to change settings by adjusting
0 to 1.

It is only the kernel
that is named Linux, the rest of the OS are GNU
tools. A package with the kernel and the needed
tools make up a Linux distribution.

href=”http://www.mandrakelinux.com/”>Mandrake ,
href=”http://www.suse.com/”>Suse,
href=”http://www.gentoo.org/”>Gentoo and Redhat are some of the
many variants. Linux OS can be used on a large
number of boxes, including i386+ , Alpha, PowerPC
and Sparc.

name=toc2>
2. Understanding files and folders

Linux is made with one thought in mind: Everything
is a file.

A blank piece of paper is called a file in the
world of computers. You can use this piece of
paper to write a text or make a drawing. Your
text or drawing is called information. A computer
file is another way of storing your information.

If you make many drawings then you will eventually
want to sort them in different piles or make some
other system that allows you to easily locate
a given drawing. Computers use folders to sort
your files in a hieratic system.

A file is an element of data storage in a file
system. Files are usually stored on harddrives,
cdroms and other media, but may also be information
stored in RAM or links to devices.

To organize our files into a system we use folders.
The lowest possible folder is root / where you
will find the user homes called /home/.

/

/home/

/home/mom/

/home/dad/

Behind every configurable option there is a simple
human-readable text file you can hand-edit to
suit your needs. These days most programs come
with nice GUI (graphical user interface) like
Mandrakes Control Center and Suses YAST that can
smoothly guide you through most configuration.
Those who choose can gain full control of their
system by manually adjusting the configuration
files from foo=yes to foo=no in an editor.

Almost everything you do on a computer involves
one or more files stored locally or on a network.

Your filesystems lowest folder root / contains
the following folders:
/bin     Essential user command binaries (for use
by all users)
/boot     Static files of the boot loader, only
used at system startup
/dev     Device files, links to your hardware devices
like /dev/sound, /dev/input/js0 (joystick)
/etc     Host-specific system configuration
/home     User home directories. This is where you
save your personal files
/lib     Essential shared libraries and kernel
modules
/mnt     Mount point for a temporarily mounted
filesystem like /mnt/cdrom
/opt     Add-on application software packages
/usr     /usr is the second major section of the
filesystem. /usr is shareable, read-only
data. That means that /usr should be shareable
between various FHS-compliant hosts and
must not be written to. Any information
that is host-specific or varies with time
is stored elsewhere.
/var     /var contains variable data files. This
includes spool directories and files, administrative
and logging data, and transient and temporary
files.
/proc     System information stored in memory mirrored
as files.

The only folder a normal user needs to use is
/home/you/ – this is where you will
be keeping all your documents.

/home/elvis/Documents

/home/elvis/Music

/home/elvis/Music/60s

Files are case sensitive, “myfile” and “MyFile”
are two different files.

For more details, check out:

3. Understanding users and permissions

Linux is based on the idea that everyone using
a system has their own username and password.

Every file belongs to a user and a group,
and has a set of given attributes (read, write
and executable) for users, groups and all (everybody).

A file or folder can have permissions that only
allows the user it belongs to to read and write
to it, allowing the group it belongs to to read
it and at the same time all other users can’t
even read the file.

4. Who and what is root

Linux has one special user called root
(this is the user name). Root is the “system administrator”
and has access to all files and folders. This
special user has the right to do anything.

You should never log on as this user unless
you actually need to do something that requires
it!

Use su – to temporary become root
and do the things you need, again: never log into
your sytem as root!

Root is only for system maintenance, this
is not a regular user.

You can execute a command as root with:

su -c ‘command done as root’

Gentoo Linux: Note that on Gentoo Linux only
users that are member of the wheel group
are allowed to su to root.
id=toc5 name=toc5>
5. Opening a command shell / terminal

To learn Linux, you need to learn the shell command
line in a terminal emulator.

In KDE: K -> System
-> Konsoll to get a command shell)

Pressing CTRL-ALT-F1 to CTRL-ALT-F6
gives you the console command shell windows, while
CTRL-ALT-F7 gives you
href=”http://www.xfree86.org/”>XFree86 (the graphical interface).

xterm
is the standard XFree console installed on all
boxes, run it with xterm (press ALT F2
in KDE and Gnome to run commands).

Terminals you probably have installed:

* xterm
href=”http://dickey.his.com/xterm/”>http://dickey.his.com/xterm/
* konsole (KDEs terminal)
* gnome-terminal (Gnomes terminal)

Non-standard terminals should install:

* rxvt
href=”http://www.rxvt.org/”>http://www.rxvt.org/
* aterm
href=”http://aterm.sourceforge.net/”>http://aterm.sourceforge.net/

6. Your first Linux commands

Now you should have managed to open a terminal
shell and are ready to try your first Linux commands.
Simply ask the computer to do the tasks you want
it to using it’s language and press the enter
key (the big one with an arrow). You can add a
& after the command to make it
run in the background (your terminal will be available
while the job is done). It can be practical to
do things like moving big divx movies as a background
process: cp movie.avi /pub &.

6.1. ls – short for list

ls lists the files in the current working folder.
This is probably the first command to try out.
It as a number of options described on the ls
manpage.

Examples:

ls

ls -al –color=yes

6.2. pwd – print name of current/working directory

pwd prints the fully resolved name
of the current (working) directory.

6.3. cd – Change directory

cd stands for change (working) directory and
that’s what it does. The folder below you (unless
you are in /, where there is no lower directory)
is called “..”.

To go one folder down:

cd ..

Change into the folder Documents in your current
working directory:

cd Documents

Change into a folder somewhere else:

cd /pub/video

The / in front of pub means that the folder pub
is located in the / (lowest folder).

7. The basic commands

7.1. chmod – Make a file executable

To make a file executable and runnable by any
user:

chmod a+x myfile name=toc12>
7.2. df – view filesystem disk space usage

df -h

Filesystem Size  Used Avail Use% Mounted on

/dev/hda3   73G   67G  2.2G  97% /

tmpfs      2.0M   24K  2.0M   2% /mnt/.init.d

tmpfs      252M     0  252M   0% /dev/shm

The flags: -h, –human-readable Appends a size
letter such as M for megabytes to each size.
id=toc13 name=toc13>
7.3. du – View the space used by files and folders

Use du (Disk Usage) to view how much space
files and folders occupy.

du is a part of
href=”http://www.gnu.org/software/fileutils/fileutils.html”>fileutils.

Example du usage:

du -sh Documents/

409M    Documents

7.4. mkdir – makes folders

Folders are created with the command mkdir:

mkdir folder

To make a long path, use mkdir -p :

mkdir -p /use/one/command/to/make/a/long/path/

Like most programs mkdir supports -v (verbose).
Practical when used in scripts.

You can make multiple folders in bash
and other shells with {folder1,folder2} :

mkdir /usr/local/src/bash/{old,new,dist,bugs}

The command rmdir removes folders.

name=toc15>
7.5. passwd – changes your login password

To change your password in Linux, type:

passwd

The root user can change the password
of any user by running passwd with the user name
as argument:

passwd jonny

will change jonnys password. Running passwd without
arguments as root changes the root password.

name=toc16>
7.5.1. KDE

From KDE you can change your password by going:

* K -> Settings
-> Change Password
* K -> Settings
-> Control Center -> System
Administration -> User Account

7.6. rm – delete files and folders, short for
remove

Files are deleted with the command rm:

rm /home/you/youfile.txt

To delete folders, use rm together with
-f (Do not prompt for confirmation) and
-r (Recursively remove directory trees):

rm -rf /home/you/foo/

Like most programs rm supports -v (verbose).
7.7. ln – make symbolic links

A symbolic link is a “file” pointing to another
file.

To make a symbolic link :

ln /original/file /new/link

This makes /original/file and /new/link the same
file – edit one and the other will change. The
file will not be gone until both /original/file
and /new/link are deleted.

You can only do this with files. For folders,
you must make a “soft” link.

To make a soft symbolic link :

ln -s /original/file /new/link

Example:

ln -s /usr/src/linux-2.4.20 /usr/src/linux

Note that -s makes an “empty” file pointing to
the original file/folder. So if you delete the
folder a symlink points to, you will be stuck
with a dead symlink (just rm it).
7.8. tar archiving utility – tar.bz2 and tar.gz

tar
is a very handle little program to store files
and folders in archives, originally made for tapestreamer
backups. Tar is usually used together with
href=”http://www.gnu.org/software/gzip/gzip.html”>gzip or
href=”http://sources.redhat.com/bzip2/”>bzip2 , comprepssion programs
that make your .tar archive a much smaller .tar.gz
or .tar.bz2 archive.

kde

You can use the program ark (K
-> Utilities -> Ark)
to handle archives in KDE. Konqueror
treats file archives like normal folders, simply
click on the archive to open it. The archive becomes
a virtual folder that can be used to open, add
or remove files just as if you were working with
a normal folder.

7.8.1. tar files (.tar.gz)

To untar files:

tar xvzf file.tar.gz

To tar files:

tar cvzf file.tar.gz filedir1 filedir2 filedir2…

Note: A .tgz file is the same as a .tar.gz file.
Both are also often refered to as tarballs.

The flags: z is for gzip, v is for verbose, c
is for create, x is for extract, f is for file
(default is to use a tape device).
id=toc21 name=toc21>
7.8.2. bzip2 files (.tar.bz2)

To unpack files:

tar xjvf file.tar.bz2

To pack files:

tar cvjf file.tar.bz2 filedir1 filedir2 filedir2…

The flags: Same as above, but with j for for
bzip2

You can also use bunzip2 file.tar.bz2 ,
will turn it into a tar.

For older versions of tar, try tar -xjvf or -xYvf
or -xkvf to unpack.There’s a few other options
it could be, they couldn’t decide which switch
to use for bzip2 for a while.

How to untar an entire directory full or archives?

.tar:

for i in `ls *.tar`; do tar xvf $i; done

.tar.gz: for i in `ls *.tar.gz`; do tar
xvfz $i; done

.tar.bz2: for i in `ls *.tar.bz2`; do tar
xvfj $i; done

Shuttleworth wants to organize major releases into three separate “waves” which would each include different components of the desktop stack. The first wave would include fundamental components like the Linux kernel, the GCC compiler, graphical toolkits like GTK+, and development platforms like Python and Java. The second wave would include the desktop environments and desktop applications, while the third wave would be the distributions.

Although a unified release cycle would reduce much of the complexity associated with building a Linux distribution, the concept poses significant challenges and offers few rewards for software developers. Achieving synchronization on the scale that Shuttleworth desires would require some open-source software projects to radically change their current development models and adopt a new approach that isn’t going to be viable for many projects.
Understanding time-based release cycles

A time-based release cycle implies issuing releases consistently at a specified interval. The development process for projects that employ this model generally involves establishing a roadmap of planned features and then implementing as many as possible until the project reaches the code-freeze stage near the end of the interval, at which point the features that haven’t been finished get deferred. The focus shifts to debugging and quality assurance until the end of the interval, when the software is officially released.

This model works well for many projects, particularly the GNOME desktop environment. One consequence of this model, however, is that it forces developers to work incrementally, and it discourages large-scale modifications that would exceed the time constraints of the cycle. Sometimes that window just isn’t large enough to merge and test major architectural changes that were incubated in parallel outside of the main code tree.

When that happens, developers have to ask themselves whether the benefits of the new features outweigh the detrimental impact of the regressions (like with the GVFS adoption in GNOME 2.22, for example). Sometimes they have to decide to pull out features at the last minute or push back the release date to allow for more debugging. These are hard choices, and, as Shuttleworth himself notes, making those choices requires a lot of discipline.

Although time-based cycles can work well for some projects, attempting to force all projects to adopt this approach and then correlate these universally could seriously degrade the development process. If projects begin to depend on synchronization, then delays at any level of the stack would cause disruption to every other layer. This could put enormous pressure on individual projects to stick to the plan, even if doing so would be detrimental to the program and to its end users.

Some of my readers today will be aware of a beautiful operating system that goes by the name of Linux. For those who are not already familiar, here is a brief introduction: Linux is a free open-source alternative to Windows and Macintosh. Based off of Unix, Linus Torvalds laid the framework for the kernel many years ago and then made the source code open to all. He still works on the kernel today, but he’s not alone; millions of programmers around the world work to improve Linux with their free time. They’ve worked hard to bring Linux to maturity, and as of the past couple years, it has reached a mature stage where the average computer user is more than capable of using it. In other words, you no longer need to know how a computer works or how to program in order for Linux to be useful to you.

So why am I bringing up this topic? Quite frankly, there aren’t enough Linux users accessing TechwareLabs, and I believe this needs to change.

Whether it’s because you’ve never heard of Linux, have an interest, or tried it years ago when it was still young and was disappointed, one thing is certain: you’re missing out. I’ll be elaborating further into Linux in future articles, but for now, here is a nice introduction.
What do you mean by open-source?

The source code is freely available on the internet per the GPL license. You are more than welcome to view the code, edit it, and republish a new product (assuming you know a thing or two about programming). The only catch is that you have to release your product under the very same GPL license.

This approach to software truly throws the concept of “proprietary” out the window, and is no doubt confusing to anybody who is business-minded. It’s a foreign concept for many as to why one would develop a product and not claim intellectual property rights. The Linux community, in general (though there are exceptions), does not seek to gain profit. Rather, they put their time into Linux for pride and the occasional “thank you.”
There are companies that sell Linux, though.

This is partially true. They’re still licensed under the GPL, which means they are required to release the source code to the general public. What companies such as Red Hat and Novell are doing is not selling the operating system, but rather they are selling support, primarily for servers. Even so, you can use their products for free. Red Hat Enterprise Linux has fees attached to it, but Red Hat sponsors an open-source community around Fedora, which is the free alternative, developed by programmers in their spare time. Similarly for Novell SUSE Linux Enterprise, there is a free alternative in openSUSE.
Windows works fine. Why should I use something else?

Here, we get to the heart of the matter. Why switch, you ask? What’s the point? Simply put, Linux is faster, more stable and above all, easier to use. The speed is due to higher efficiency in storing/retrieving information. The issue of stability isn’t even questioned by [knowledgeable] die-hard Windows fans. Ultimately, the most controversial claim I’ve made is that it’s easier to use.

This is where the argument rages on within the desktop market. There are many long-time Windows users who try Linux, and are scared off, upon which they claim that Linux is hard to use. The fact is, Linux is different, but I would argue that this is a good thing. There is definitely a learning curve, as there always is when you try something new, but the more you just play around with Linux, the more you’ll find it is simply better.
How is it better? What makes it easier?

Everything is better organized. For starters, you know that little program on Windows, Add/Remove Programs? Raise your hand if you’ve ever actually “added” a program using it.

I see a few hands from people who have via a NT system or something similar, but other than that, it is unlikely you’ve used Add/Remove for anything other than “remove” (though Vista does allow for the user to download programs directly from Microsoft, a feature suspiciously appearing long after Linux started doing the exact same thing). In Linux, this little program is called the “package manager”, and this is where you both add AND remove your programs. Everything that’s currently installed, as well as everything you’re able to install from the supplied servers appears in an easy-to-use catalog. For the most part, everything you need is right there in one place. Want to install an office suite? How about an IM program? Or how about a game? Just go to the respective section and choose the program you want. Check the boxes for everything you want to change (install/uninstall) and push the appropriate button to update your system (specifics will differ depending on the package manager used by the distribution).

This article is about operating systems that use the Linux kernel. For the kernel itself, see Linux kernel. For other uses, see Linux (disambiguation).
Linux
Tux, the penguin, mascot of Linux
Tux, the penguin, mascot of the Linux kernel
OS family Unix-like
Latest stable release 2.6.23.12 (Linux kernel) / 18 December 2007
Kernel type Monolithic kernel
License GNU General Public License and others
Working state Current

Linux (pronunciation: IPA: /?l?n?ks/, lin-uks) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; typically all underlying source code can be freely modified, used, and redistributed by anyone.

The Linux kernel was first released to the public on 17 September 1991, for the Intel x86 PC architecture. The kernel was augmented with system utilities and libraries from the GNU project to create a usable operating system, which led to an alternative term, GNU/Linux. Linux is packaged for different uses in Linux distributions, which contain the sometimes modified kernel along with a variety of other software packages tailored to different requirements.

Predominantly known for its use in servers, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, supercomputers, video game systems, such as PlayStation 2, 3, several arcade games, and embedded devices, such as mobile phones and routers.

In 1992, Linus Torvalds explained that he pronounces Linux as /?l?n?ks/, though other variations are common.

The Unix operating system was conceived and implemented in the 1960s and first released in 1970. Its wide availability and portability meant that it was widely adopted, copied and modified by academic institutions and businesses, with its design being influential on authors of other systems.

he GNU Project, started in 1984, had the goal of creating a “complete Unix-compatible software system” made entirely of free software. In 1985, Richard Stallman created the Free Software Foundation and developed the GNU General Public License (GNU GPL), in order to spread software freely. Many of the programs required in an OS (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed by the early 1990s, although low level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has said that if the GNU kernel had been available at the time (1991), he would not have decided to write his own.

MINIX, a Unix-like system intended for academic use, was released by Andrew S. Tanenbaum in 1987. While source code for the system was available, modification and redistribution were restricted. In addition, MINIX’s 16-bit design was not well adapted to the 32-bit design of the increasingly cheap and popular Intel 386 architecture for personal computers.

In 1991, Linus Torvalds began to work on a non-commercial replacement for MINIX while he was attending the University of Helsinki. This eventually became the Linux kernel.

Linux was dependent on the MINIX userspace at first. With code from the GNU system freely available, it was advantageous if this could be used with the fledgling OS. Code licensed under the GNU GPL can be used in other projects, so long as they also are released under the same or a compatible license. In order to make the Linux kernel compatible with the components from the GNU Project, Torvalds initiated a switch from his original license (which prohibited commercial redistribution) to the GNU GPL. Linux and GNU developers worked to integrate GNU components with Linux to make a fully functional and free operating system.

Commercial and popular uptake

Today Linux is used in numerous domains, from embedded systems to supercomputers, and has secured a place in server installations with the popular LAMP application stack. Torvalds continues to direct the development of the kernel. Stallman heads the Free Software Foundation, which in turn supports the GNU components. Finally, individuals and corporations develop third-party non-GNU components. These third-party components comprise a vast body of work and may include both kernel modules and user applications and libraries. Linux vendors and communities combine and distribute the kernel, GNU components, and non-GNU components, with additional package management software in the form of Linux distributions.

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 the best-known and most widely used. Some free and open source software licences 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 GPL, is used for the Linux kernel and many of the components from the GNU project.

As an operating system underdog competing with mainstream operating systems, Linux cannot rely on a monopoly advantage; in order for Linux to be convenient for users, Linux aims for interoperability with other operating systems and established computing standards. Linux systems adhere to POSIX, SUS, ISO, and ANSI standards where possible, although to date only one Linux distribution has been POSIX.1 certified, Linux-FT.

Free software projects, although developed in a collaborative fashion, are often produced independently of each other. However, given that the software licenses explicitly permit redistribution, this provides a basis for larger scale projects that collect the software produced by stand-alone projects and make it available all at once in the form of a Linux distribution.

A Linux distribution, commonly called a “distro”, is a project that manages a remote collection of Linux-based software, and facilitates installation of a Linux operating system. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. They include system software and application software in the form of packages, and distribution-specific software for initial system installation and configuration as well as later package upgrades and installs. A distribution is responsible for the default configuration of installed Linux systems, system security, and more generally integration of the different software packages into a coherent whole.

Linux is largely driven by its developer and user communities. Some vendors develop and fund their distributions on a volunteer basis, Debian being a well-known example. Others maintain a community version of their commercial distributions, as Red Hat does with Fedora.

In many cities and regions, local associations known as Linux Users Groups (LUGs) seek to promote Linux and by extension free software. They hold meetings and provide free demonstrations, training, technical support, and operating system installation to new users. There are also many Internet communities that seek to provide support to Linux users and developers. Most distributions and open source projects have IRC chatrooms or newsgroups. Online forums are another means for support, with notable examples being LinuxQuestions.org and the Gentoo forums. Linux distributions host mailing lists; commonly there will be a specific topic such as usage or development for a given list.

There are several technology websites with a Linux focus. Linux Weekly News is a weekly digest of Linux-related news; the Linux Journal is an online magazine of Linux articles published monthly; Slashdot is a technology-related news website with many stories on Linux and open source software; Groklaw has written in depth about Linux-related legal proceedings; and there are many articles relevant to the Linux kernel and its relationship with the GNU on the project’s website.

Although Linux is generally available free of charge, several large corporations have established business models that involve selling, supporting, and contributing to Linux and free software. These include Dell, IBM, HP, Sun Microsystems, Novell, and Red Hat. The free software licenses on which Linux is based explicitly accommodate and encourage commercialization; the relationship between Linux as a whole and individual vendors may be seen as symbiotic. One common business model of commercial suppliers is charging for support, especially for business users. A number of companies also offer a specialized business version of their distribution, which adds proprietary support packages and tools to administer higher numbers of installations or to simplify administrative tasks. Another business model is to give away the software in order to sell hardware.

Programming on Linux

Most Linux distributions support dozens of programming languages. The most common collection of utilities for building both Linux applications and operating system programs is found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system. Amongst others, GCC provides compilers for C, C++, Java, Ada and Fortran. The Linux kernel itself is written to be compiled with GCC.

Most also include support for Perl, Ruby, Python and other dynamic languages. Examples of languages that are less common, but still well-supported, are C# via the Mono project, and Scheme. A number of Java Virtual Machines and development kits run on Linux, including the original Sun Microsystems JVM (HotSpot), and IBM’s J2SE RE, as well as many open-source projects like Kaffe. The two main frameworks for developing graphical applications are those of GNOME and KDE. These projects are based on the GTK+ and Qt widget toolkits, respectively, which can also be used independently of the larger framework. Both support a wide variety of languages. There are a number of Integrated development environments available including Anjuta, Code::Blocks, Eclipse, KDevelop, MonoDevelop, NetBeans, and Omnis Studio while the traditional editors Vim and Emacs remain popular.

Although free and open source compilers and tools are widely used under Linux, there are also proprietary solutions available from a range of companies, including the Intel C++ Compiler, PathScale, Micro Focus COBOL, Franz Inc and the Portland Group.

Design

Linux is a modular Unix-like operating system. It derives much of its basic design from principles established in Unix during the 1970s and 1980s. Linux uses a monolithic kernel, the Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel.

Much of Linux’s higher-level functionality is provided by separate projects which interface with the kernel. The GNU userland is an important part of most Linux systems, providing the shell and Unix tools which carry out many basic operating system tasks. Atop these tools graphical user interfaces can be placed, usually running via the X Window System.

User interface

See also: User interface

Linux can be controlled by one or more of a text-based command line interface (CLI), graphical user interface (GUI) (usually the default for desktop), through controls on the device itself (common on embedded machines).

On desktop machines, KDE, GNOME and Xfce are the most popular user interfaces., though a variety of other user interfaces exist. Most popular user interfaces run on top of the X Window System (X), which provides network transparency, enabling graphical apps running on one machine to be displayed and controlled from another.

Other GUIs include X window managers such as FVWM, Enlightenment and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X window system.

As with most platforms there are a number of toolkits. These tend to be themed similarly in order to maintain desktop continuity. For example, although Evolution is based on GTK, Firefox is based on XUL, OpenOffice.org is based on its own toolkit and Azureus is a Java app, each uses the same GTK theme and is similar in appearance.

Linux systems usually provide a CLI of some sort through a shell, which is the traditional way of interacting with Unix systems. Linux distributions specialized for servers may use the CLI as their only interface. “Headless systems” run without even a monitor can be controlled by command line via a protocol such as SSH or telnet.

Most low-level Linux components, including the GNU Userland, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. Graphical terminal emulator programs are often used to access the CLI from a Linux desktop.

Uses

As well as those designed for general purpose use on desktops and servers, distributions may be specialized for different purposes including: computer architecture support, embedded systems, stability, security, localization to a specific region or language, targeting of specific user groups, support for real-time applications, or commitment to a given desktop environment. Furthermore, some distributions deliberately include only free software. Currently, over three hundred distributions are actively developed, with about a dozen distributions being most popular for general-purpose use.

Linux is a widely ported operating system. While the Linux kernel was originally designed only for Intel 80386 microprocessors, it now runs on a more diverse range of computer architectures than any other operating system—from the hand-held ARM-based iPAQ to the mainframe IBM System z9, in devices ranging from supercomputers to mobile phones. Specialized distributions exist for less mainstream architectures. The ELKS kernel fork can run on Intel 8086 or Intel 80286 16-bit microprocessors, while the µClinux kernel may run on systems without a memory management unit. The kernel also runs on architectures that were only ever intended to use a manufacturer-created operating system, such as Macintosh computers, PDAs, Video game consoles, portable music players, and Mobile phones.

Although in specialized application domains such as desktop publishing and professional audio there may be a lack of commercial quality software, users migrating from Mac OS X and Windows can find equivalent applications for most tasks.

Many free software titles that are popular on Windows are also available, such as Pidgin, Mozilla Firefox, Openoffice.org, and GIMP, amongst others. A growing amount of proprietary desktop software is also supported under Linux, examples being Adobe Flash Player, Acrobat Reader, Matlab, Nero Burning ROM, Opera, RealPlayer, and Skype. In the field of animation and visual effects, most high end software, such as AutoDesk Maya, Softimage XSI and Apple Shake are available both for Linux, Windows and/or MacOS X. Additionally, CrossOver is a commercial solution based on the open source Wine project that supports running Windows versions of Microsoft Office and Photoshop.

Linux’s open nature offers the ability for distributed teams to localize Linux distributions for use in locales where doing so to proprietary systems would not be cost-effective. For example, the Sinhalese language version of the Knoppix distribution was available for a long time before the initiation of translation of Microsoft Windows XP to Sinhalese. In this case, The Lanka Linux User Group played a major part in developing the localized system by combining the knowledge of university professors, linguists and local developers.

Servers and supercomputers

Historically, Linux has mainly been used as a server operating system, and has risen to prominence in that area; Netcraft reported in September 2006 that eight of the ten most reliable internet hosting companies run Linux on their web servers. This is due to its relative stability and long uptime, and the fact that desktop software with a graphical user interface is often unneeded. Enterprise and non-enterprise Linux distributions may be found running on servers. Linux is the cornerstone of the LAMP server-software combination (Linux, Apache, MySQL, Perl/PHP/Python) which has achieved popularity among developers, and which is one of the more common platforms for website hosting.

Linux is commonly used as an operating system for supercomputers. As of November 2007, out of the top 500 systems, 426 (85.2%) run Linux.

Embedded devices

Main article: embedded Linux

Due to its low cost and ability to be easily modified, an embedded Linux is often used in embedded systems. Linux has become a major competitor to the proprietary Symbian OS found in many mobile phones — 16.7% of smartphones sold worldwide during 2006 were using Linux — and it is an alternative to the dominant Windows CE and Palm OS operating systems on handheld devices. The popular TiVo digital video recorder uses a customized version of Linux. Several network firewall and router standalone products, including several from Linksys, use Linux internally, using its advanced firewall and routing capabilities. The Korg OASYS and the Yamaha Motif XS music workstations also run Linux.

Many quantitative studies of open source software focus on topics including market share and reliability, with numerous studies specifically examining Linux. The Linux market is growing rapidly, and the revenue of servers, desktops, and packaged software running Linux is expected to exceed $35.7 billion by 2008.

IDC’s report for Q1 2007 says that Linux now holds 12.7% of the overall server market. This estimate was based on the number of Linux servers sold by various companies.

Desktop adoption of Linux is approximately 1%. In comparison, Microsoft operating systems hold more than 90%.

The frictional cost of switching operating systems and lack of support for certain hardware and application programs designed for Microsoft Windows have been two factors that have inhibited adoption. Proponents and analysts attribute the relative success of Linux to its security, reliability, low cost, and freedom from vendor lock-in.

The XO laptop project of One Laptop Per Child is creating a new and potentially much larger Linux community, planned to reach several hundred million schoolchildren and their families and communities in developing countries. Six countries have ordered a million or more units each for delivery in 2007 to distribute to schoolchildren at no charge. Google, Red Hat, and eBay are major supporters of the project.

GNU/Linux

Main article: GNU/Linux naming controversy

The Free Software Foundation views Linux distributions which use GNU software as “GNU variants” and they ask that such operating systems be referred to as GNU/Linux or a Linux-based GNU system. However, the media and population at large refers to this family of operating systems simply as Linux. While some distributors make a point of using the aggregate form, most notably Debian with the Debian GNU/Linux distribution, the term’s use outside of the enthusiast community is limited. The distinction between the Linux kernel and distributions based on it plus the GNU system is a source of confusion to many newcomers, and the naming remains controversial.