Unix / Linux Fundanmetals

Linux Ideas and History• Linux originated at 1991 at the Helsinki university by a

student named Linus Torvalds with the intention of developing an open-source kernel to run on Intel-compatible hardware. Linus used the GNU project’s software under his kernel.

• The GNU project’s beginning goes back almost 10 years prior to Linus’ kernel development, its father is Richard Stallman and it was designed create open-source alternatives to all utilities and applications that run under UNIX.

• The GNU project has brought forth highly known and used software such as the BASH shell and the “gcc” compiler however the most important thing it brought was the GPL (General Public License) which legally defines and secures a software as being “open-source”.

What is Linux?• Linux is a UNIX-based operating system originally designed to

function on Intel-based hardware. Today, Linux can be found on many different hardware platforms such as: Cell-phones and Tablets (Google’s Android OS), various vendor specific server-hardware, x86/x86_64 based hardware and there was even a wristwatch developed by IBM at 2001 which ran Linux.

• Linux is a modern OS, meaning uses features such as virtual memory, memory protection and preemptive multitasking.

• The development of Linux goes on by a large community of users and developers worldwide. These people see Linux as an alternative to proprietary systems such as MS Windows / Apple Macintosh / UNIX.

Why Use Linux?• Some of the reasons to use Linux are:

– Configurability– Convenience– Stability– Community– Freedom

Let’s break down and explain these advantages:

Configurability• Linux gives the end-user full access to configure just about

any aspect of their system; Customization options range from simple actions such as changing the background image in a graphical desktop environment to some more esoteric actions, such as making the "Caps Lock" key behave as the “CTRL” key.

• Linux allows the user to automate just about any task using its advanced scripting and programming capabilities, which are standard features.

• Linux, being an open-source system, offers the source-code of its software and even of the kernel itself so that users can modify them to fit their own specific needs.

Convenience• While Linux may require a little bit of work to initially set-up a

flowing and working environment, it is a very low-maintenance system after finishing the set-up process.

• Package management is as simple as running a few single commands in the shell or point-and-click if using a graphical desktop environment.

• Linux offers a complete suite of remote-access options which allow access to the system’s shell (over SSH) or the graphical desktop environment, if using one, via VNC; There are numerous additional advanced methods of gaining access to a Linux system.

Stability• Linux is based on the UNIX kernel which include features such

as preemptive multitasking and protected memory.– Preemptive Multitasking: prevents applications from “stealing” all of

the CPU and causing the system to lock-up.– Protected Memory: Prevents applications from interfering with each

others’ memory thus preventing them from crashing each other.

• Linux and its related tools are, as said before, open-source programs and as such the code is available to the public to further develop. There are many developers worldwide who keep working on that code, whether they are the original creators of it or not, resulting in bugs being fixed very quickly by those who find them instead of waiting to the next release or hotfix of the software in order to repair its bugs.

Community• Linux is part of a greater open-source community, consisting

of thousands of developers and many more users worldwide. These people, who make the community, are also its technical support force.

• There are mailing lists to just about any open-source project out there where users can communicate with each other and the project’s developers.

• There are many open-source and Linux related forums, where problems and their solutions and/or workarounds are posted. One of the bigger forums is: www.linuxquestions.org

• Free Linux tutorials, step-by-step guides and information is available online to all user proficiency levels.

Freedom• Linux is completely free, that means more than just the

system not costing money but also that you can do with it whatever you like.

• There is one restriction: even if one does sell a Linux distribution, the same way RedHat, SuSE and Mandrake do, they must grant full access to the source codes used by them, which also include the kernel sources; This restriction prevents a corporation from using the Linux kernel as a base to a proprietary operating-system of their own.

Generic Public License• As many other ‘Open Source’ projects, Linux is registered

under the Generic Public License (GPL), which includes the following rules and restrictions– You can review, modify and use the source code in any way– In case you choose to change the code and publish a modified

application (commercial or public) you must provide the source code for the Entire application, both the original GPL and the newly added features

– You can sell, distribute or give any GPL application, as long as you provide the source code of that application with it

Distribution• Linux has many distributions. Distribution refers to an

open-source project that includes a full featured operating system based on the Linux Kernel

• These distributions usually make a vast use of the GNU tool kit and other open-source project such as: – X.org– Apache– GIMP– BIND

• Each distribution is intended for a certain audience, several are for IT professionals, other for Developers and many are for general or specific usage users (Audio/Video Editors, Graphic Editors, etc)

Distribution• Red Hat and SuSe are two of the oldest distributions for IT

general purposes.Currently both groups are commercial companies, which provides support services for Linux and sell Licensed Enterprise Linux EditionsBoth companies have a free version of their distributions(Fedora and openSuSe)

• Debian is a distribution vastly used by Developers.Being an open-source project, several ‘child’ distributions have appeared during the years such as Ubuntu which targets home / desktop users