Learning Linux Part 1/15: All about linux
Today the first part of the learning linux series.
I write this whole learning thing as my contribution to the linux society.
THE HISTORY
To understand what this is all about, we have to go back to the history first. How was linux born exactly?
Linux was born as a deriative of Unix. Unix itselves was born 1969 in a laboratory of Bell-Telephone on an old DEC-computer.
In 1970 the very first version of Unix was released by Ken Thompson and Dennis Ritchie.
The several Unix versions that came from this version were seperated into 2 major releases:
- BSD-Unix - the unix version developed at the Berkeley University
- System V - the evolved version of unix that was originally created by Bell
Linux itself was born out of the Unix clone Minix ( which was developed by Andre Tanenbaum ). Linus Torvalds used this Unix clone to create a free operating system "Linux".
The current features of Linux are:
- open source ( the source code is availabe for everybody )
- multi-tasking ( running several tasks at the same time )
- multi-processing ( running multiple processes at the same time )
- multi-user ( support for multiple users )
- multi-platform ( support for multiple platforms i386, i686, x86_64, arm, powerpc )
- multiple shells ( running multiple shells )
THE KERNEL
The kernel is the heart of Linux and is developed by a large group of developers on the Internet. Its responsibilities include managing the system's resources (the communication between hardware and software components).
The Linux kernel version numbering scheme consists in most cases of 4 characters (A.B.C.D):
- A and B are largely irrelevant
- C is the version of the kernel
- D accounts for bug and security fixes (only) to the C version (all development occurs on release candidates—'rc')
GNU ( GNU NOT UNIX )
Every linux installation uses several GNU utilities. GNU tools are the same tools like the average Unix tools on commercial distributions, but without any costs. The tools/utilities have been provided under the conditions of the GPL ( General Public License ). All the software with the GPL License may be used, copied and modified by everybody, as long as the modifications are also provided under the conditions of the GPL License. An example of a famous GNU tool is GIMP ( GNU Image Manipulation Program ).
X WINDOW SYSTEM
X delivers X-servers which are responsible for the management of the graphical card in the computer. A deriative of X is XFree86, which is a project which aims to deliver a X implementation for the pc architecture. Another X implementation is Xorg, which is an opensource version of X which is used on most modern linux distributions.
WINDOW MANAGERS AND DESKTOP ENVIRONMENTS
X alone can do no more then showing a background with an unresizable window. That's why X is always used in combination with a Window Manager or Desktop Environment. At this moment the two largest Desktop Environments are Gnome and KDE. Popular Window Managers are Fluxbox, FVWM, IceWM, Ion3 and more... ( http://xwinman.org/ )
NETWORKING
TCP/IP Networking is another component that is strongly integrated into Linux. The integration is done into two ways:
1. Big parts of the kernel are based on the functionality of the TCP/IP protocol.
2. Almost every linux distribution comes with tools to enable TCP/IP networking
LICENSE
One of the most important reasons of the success of Linux is it's license. Linux is opensource which means that it's source code is freely available. A lot of people think that opensource equals free. That's a very common misunderstanding, just try to walk out of a book store with the latest SUSE Version in your hand 
. Opensource is free as in freedom of mind, not as in free beer.
DISTRIBUTIONS
Some very popular linux distributions are the following:
SUSE - his is a linux distribution with good support and aims for both home users and professional users.
RedHat - One of the largest commercial linux distributions with commercial support. Fedora linux is the opensource version variant of this distribution.
Mandriva - Started as a Redhat clone with the KDE desktop environment. Nowdays it's not a clone anymore but an independant linux distribution which is famous because of it's intuitve management tools.
Debian - A community based non-commercial linux distribution which is maintaoned by the opensource community. This is a very stable with a high learning curve. This makes it a non beginners distribution.
Knoppix - The linux distribution that is often used as a rescue tool for computers with broken linux or windows installations.
POPULAR LINUX SERVICES
Some of the most popular linux services are:
- Apache - The most used webserver on the internet (70% of the whole internet).
- Squid - Linux webproxy with content filtering and caching function
- Samba - Windows file sharing server. Uses the SMB protcol to exchange data between computers.
- Sendmail - SMTP ( Simple Mail Transfer Protocol ) MailServer.
- Netfilter - Technique which is used to filter network traffic ( for example used in firewalls )
- DNS - BIND - DNS server which is fully RFC compatible
