Saturday, October 3, 2015

Introduction to GNU/LINUX

What Is Linux? Introduction to Linux Operating System
                    For detailed notes in pdf click here
Linux is a UNIX-base operating system. Its original creator was a Finnish student name Linus Torvalds, although being ‘open source’ it has change a great deal since its original conception. It belongs to nobody, and is free to download and use. Any changes to it are open for all to adopt, and as a result it has developed into a very powerful OS that is rapidly gaining in popularity worldwide, particularly among those seeking an alternative to Windows.
In 1991, hardware was expanding rapidly, and DOS was the king of operating systems. Software development was slower, and Macs, while better, were also much pricier than PCs. UNIX was growing, but at that time in its history the source code was jealously guarded and expensive to use.
Linus Torvalds was a Helsinki university student who liked playing around with software and computers, and in 1991 he announced the creation of a new core operating system that he had named Linux. It is now one of the most used systems for the PC, and is particularly suitable for businesses with small IT budgets. Linux is free to use and install, and is more reliable than almost all other systems, running for many months and even years without a reboot being necessary.
Advantages and Benefits of Linux
One of the significant benefits of open source software such as Linux is that because it has no owner, it can be debugged without resource to a license owner or software proprietor. Businesses therefore have the flexibility to do as they wish with the OS without having to worry about conforming to complex license agreements.
The major advantage of Linux is its cost: the core OS is free, while many software applications also come with a GNU General public License. It can also be used simultaneously by large numbers of users without slowing down or freezing and it is very fast. It is an excellent networking platform and performs at optimum efficiency even with little available hard disk space.
Linux also runs on a wide range of hardware types, including PCs, Macs, mainframes, supercomputers, some cell phones and industrial robots. Some prefer to dual-boot Linux and Windows while others prefer Linux and Mac OS. System76 machines come pre-installed with Linux in the form of Ubuntu, a Debian distribution of Linux. This is the most popular distribution of Linux for laptops.
Linux Vs Windows
The main benefits and advantages of Linux over other operating systems, particularly Microsoft Windows, are:
• It is free to use and distribute.
• Support is free through online help sites, blogs and forums.
• It is very reliable – more so than most other operating systems with very few crashes.
• A huge amount of free open source software has been developed for it.
• It is very resistant to malware such as spyware, adware and viruses.
• It runs in a wide variety of machines than cannot be updated to use newer Windows versions.
• Since the source code is visible, ‘backdoors’ are easily spotted, so Linux offers greater security for sensitive applications.
• Linux offers a high degree of flexibility of configuration, and significant customization is possible without modifying the source code.
The Linux operating system is widely use by both home and business users, and its usage is increasing daily. It is considered that Linux will eventually overtake Microsoft Windows as the most popular operating system, which could also open the door further for more free software such as Open Office, The Gimp, Paint, Thunderbird, Firefox and Scribus. It is easy to install and run alongside your existing operating system, so give it a try, because it is also easy to remove if you don’t like it – which is unlikely.

1.1.         History 1.1.1. UNIX
In order to understand the popularity of Linux, we need to travel back in time, about 30 years ago... Imagine computers as big as houses, even stadiums. While the sizes of those computers posed substantial problems, there was one thing that made this even worse: every computer had a different operating system. Software was always customized to serve a specific purpose, and software for one given system didn't run on another system. Being able to work with one system didn't automatically mean that you could work with another. It was difficult, both for the users and the system administrators. Computers were extremely expensive then, and sacrifices had to be made even after the original purchase just to get the users to understand how they worked. The total cost per unit of computing power was enormous. Technologically the world was not quite that advanced, so they had to live with the size for another decade. In 1969, a team of developers in the Bell Labs laboratories started working on a solution for the software problem, to address these compatibility issues. They developed a new operating system, which was
1. Simple and elegant.
2. Written in the C programming language instead of in assembly code.
3. Able to recycle code.

The Bell Labs developers named their project "UNIX." The code recycling features were very important. Until then, all commercially available computer systems were written in a code specifically developed for one system. UNIX on the other hand needed only a small piece of that special code, which is now commonly named the kernel. This kernel is the only piece of code that needs to be adapted for every specific system and forms the base of the UNIX system. The operating system and all other functions were built around this kernel and written in a higher programming language, C.
This language was especially developed for creating the UNIX system. Using this new technique, it was much easier to develop an operating system that could run on many different types of hardware. The software vendors were quick to adapt, since they could sell ten times more software almost effortlessly. Weird new situations came in existence: imagine for instance computers from different vendors communicating in the same network, or users working on different systems without the need for extra education to use another computer. UNIX did a great deal to help users become compatible with different systems. Throughout the next couple of decades the development of UNIX continued. More things became possible to do and more hardware and software vendors added support for UNIX to their products. UNIX was initially found only in very large environments with mainframes and minicomputers (note that a PC is a "micro" computer). You had to work at a university, for the government or for large financial corporations in order to get your hands on a UNIX system. But smaller computers were being developed, and by the end of the 80's, many people had home computers. By that time, there were several versions of UNIX available for the PC architecture, but none of them were truly free and more important: they were all terribly slow, so most people ran MS DOS or Windows 3.1 on their home PCs.
1.1.2. Linus and Linux
By the beginning of the 90s home PCs were finally powerful enough to run a full blown UNIX. Linus Torvalds, a young man studying computer science at the university of Helsinki, thought it would be a good idea to have some sort of freely available academic version of UNIX, and promptly started to code. He started to ask questions, looking for answers and solutions that would help him get UNIX on his PC. Below is one of his first posts in comp.os.minix, dating from 1991:
From the start, it was Linus' goal to have a free system that was completely compliant with the original UNIX. That is why he asked for POSIX standards, POSIX still being the standard for UNIX. In those days plug-and-play wasn't invented yet, but so many people were interested in having a UNIX system of their own, that this was only a small obstacle. New drivers became available for all kinds of new hardware, at a continuously rising speed. Almost as soon as a new piece of hardware became available, someone bought it and submitted it to the Linux test, as the system was gradually being called, releasing more free code for an ever wider range of hardware. These coders didn't stop at their PC's; every piece of hardware they could find was useful for Linux. Back then, those people were called "nerds" or "freaks", but it didn't matter to them, as long as the supported hardware list grew longer and longer. Thanks to these people, Linux is now not only ideal to run on new PC's,
Linux isn’t a complete operating system — it’s just a kernel. Linux distributions take the Linux kernel and combine it with other free software to create complete packages. There are many different Linux distributions out there.

If you want to “install Linux,” you’ll need to choose a distribution. You could also use Linux From Scratch to compile and assemble your own Linux system from the ground up, but that’s a huge amount of work.
Ubuntu is probably the most well-known Linux distribution. Ubuntu is based on Debian, but it has its own software repositories. Much of the software in these repositories is synced from Debian’s repositories.
The Ubuntu project has a focus on providing a solid desktop (and server) experience, and it isn’t afraid to build its own custom technology to do it. Ubuntu used to use the GNOME 2 desktop environment, but it now uses its own Unity desktop environment. Ubuntu is even building its own Mir graphical server while other distributions are working on the Wayland.
Ubuntu is modern without being too bleeding edge. It offers releases every six months, with a more stable LTS (long term support) release every two years. Ubuntu is currently working on expanding the Ubuntu distribution to run on smartphones and tablets.

Mint is a Linux distribution built on top of Ubuntu. It uses Ubuntu’s software repositories, so the same packages are available on both. Originally, Mint was an alternative distribution loved mainly because it included media codecs and proprietary software that Ubuntu didn’t include by default.
This distribution now has its own identity. You won’t find Ubuntu’s own Unity desktop here — instead, you get a more traditional Cinnamon or MATE desktop. Mint takes a more relaxed approach to software updates and won’t automatically install critical software updates. Controversially, this has led some Ubuntu developers to label it insecure.
Debian is an operating system composed only of free, open-source software. The Debian project has been operating since 1993 — over 20 years ago! This widely respected project is still releasing new versions of Debian, but it’s known for moving much more slowly than distributions like Ubuntu or Linux Mint. This can make it more stable and conservative, which is ideal for some systems.
Ubuntu was originally founded to take the core bits of stable Debian and improve on them more quickly, packaging the software together into a user-friendly system that’s more frequently updated.
Fedora is a project with a strong focus on free software — you won’t find an easy way to install proprietary graphics drivers here, although third-party repositories are available. Fedora is bleeding edge and contains the latest versions of software.
Unlike Ubuntu, Fedora doesn’t make its own desktop environment or other software. Instead, the Fedora project uses “upstream” software, providing a platform that integrates all this upstream software without adding their own custom tools or patching it too much. Fedora comes with the GNOME 3 desktop environment by default, although you can also get “spins” that come with other desktop environments.
Fedora is sponsored by Red Hat, and is the foundation for the commercial Red Hat Enterprise Linux project. Unlike RHEL, Fedora is bleeding edge and not supported for long. If you want a more stable release that’s supported for longer, Red Hat would prefer you use their Enterprise product.
Red Hat Enterprise Linux is a commercial Linux distribution intended for servers and workstations. It’s based on the open-source Fedora project, but is designed to be a stable platform with long-term support.
Red Hat uses trademark law to prevent their official Red Hat Enterprise Linux software from being redistributed. However, the core software is free and open-source. CentOS is a community project that takes the Red Hat Enterprise Linux code, removes all Red Hat’s trademarks, and makes it available for free use and distribution. It’s a free version of RHEL, so it’s good if you want a stable platform that will be supported for a long time. CentOS and Red Hat recently announced they’re collaborating, so CentOS is now part of Red Hat itself.
openSUSE is a community-created Linux distribution sponsored by Novell. Novell purchased SuSE Linux in 2003, and they still create an enterprise Linux project known as SUSE Linux Enterprise. Where Red Hat has the Fedora project that feeds into Red Hat Enterprise Linux, Novell has the openSUSE project that feeds into SUSE Linux Enterprise.
Like Fedora, openSUSE is a more bleeding edge version of Linux. SUSE was once one of the great user-friendly desktop Linux distributions, but Ubuntu eventually took that crown.
Mageia is a fork of Mandriva Linux created in 2011. Mandriva — known as Mandrake before that — was once one of the great user-friendly Linux distributions.
Like Fedora and openSUSE, this is a community-created project to create an open-source Linux distribution. Mandriva SA no longer creates a consumer Linux distribution for desktop PCs, but their business Linux server projects are based on Mageia code — just like how Fedora and openSUSE provide code to their enterprise equivalents.
Arch Linux is more old school than many of the other Linux distributions here. It’s designed to be flexible, lightweight, minimal, and to “Keep it Simple.” Keeping it simple doesn’t mean Arch provides tons of graphical utilities and automatic configuration scripts to help you set up your system. Instead, it means Arch dispenses with that stuff and gets out of your way.
You’re in charge of configuring your system properly and installing the software you like. Arch doesn’t provide an official graphical interface for its package manager or complex graphical configuration tools. Instead, it provides clean configuration files designed for easy editing. The installation disc dumps you at a terminal, where you’ll need to enter the appropriate commands to configure your system, partition your disks, and install the operating system yourself.
Arch uses a “rolling release” model, which means any installation image is just a snapshot of the current software. Every bit of software will be updated over time without you needing to upgrade to a new “release” of Arch.
This distribution has a bit in common with Gentoo, which was popular at one time. Both Linux distributions are designed for users who know how their systems work or who are at least willing to learn. However, Arch uses binary packages while Gentoo had an (unnecessary) focus on compiling every bit of software from source — this means it’s quick to install software on Arch as you don’t have to spend CPU cycles and time waiting for software to compile.
Slackware is another institution. Founded in 1993, Slackware is the oldest Linux distribution that’s still maintained and putting out new releases today.
Its pedigree shows — like Arch, Slackware dispenses with all those unnecessary graphical tools and automatic configuration scripts. There’s no graphical installation procedure — you’ll have to partition your disk manually and then run the setup program. Slackware boots to a command-line environment by default. It’s a very conservative Linux distribution.
Puppy Linux is another fairly well-known Linux distribution. Previous versions have been built on Ubuntu, but the latest is built on Slackware. Puppy is designed to be a small, lightweight operating system that can run well on very old computers. The puppy ISO file is 161 MB, and Puppy can boot from that disc in a live environment. Puppy can run on PCs with 256 MB or RAM, although it does recommend 512 MB for the best experience.
Puppy isn’t the most modern and doesn’t have all the flashiest bells and whistles, but it can help you revive an old PC.

These aren’t the only Linux distributions out there. Distrowatch lists many and tries to rank them by popularity.

For more detainled list of linux distibutions click here 

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