Module 4 Open Source Linux Open Source Linux

MODULE OVERVIEW Part 1 What is Linux? Part 2 Linux Community & Open Source Part 3 Overview of Linux Features Part 4 Linux Command Line & File Structure

Part 1 What is Linux?

History of Linux In order to understand the history of Linux, we need to travel back in time, about 40 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.

Linux History 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. 1969, a team of developers in the Bell Labs laboratories started working on a solution for the software problem, to address these compatibility issues. It was named as Unix.

Linux History Unix was originally free, and source code were available By late 1980s, it became commercial, expensive and non-available source code Then Minix enters the scene created by Prof.Andrew Tanenbaum Minix is an education resource not a usable system.

Linux In 1991, Linus Benedict Torvalds created Linux. He is a 2 nd year Computer Science Student at University of Helsinki, Finland. Features of Linux includes: –Open Source and Free –Community development and Internet Release –Monolithic architecture, uses GNU –POSIX and UNIX compatible

Linux and Other OS

Linux Distribution Provides a complete usable system It includes: –One version of kernel –An install system, device drivers, ultilities, and networking –A software package system, selection, and update mechanism.

Linux Distribution

RedHat – the most popular Linux. Slackware – the first Linux distribution Mandrake – Competitiors to RedHat Lindows – it has most Linux and Windows capabilities SuSE, Debian, Fedora, Knoppix, Ubuntu, etc.

Part 2 Linux Community

Linux by its nature is a community. The OS and applications only move forward by the help by many in the community. Applications include OpenOffice which is an alternative apart from Microsoft Office. The idea behind Open Source software is rather simple: when programmers can read, distribute and change code, the code will mature.

Linux Community People can adapt it, fix it, debug it, and they can do it at a speed that dwarfs the performance of software developers at conventional companies. This software will be more flexible and of a better quality than software that has been developed using the conventional channels, because more people have tested it in more different conditions than the closed software developer ever can.

Linux Community The Open Source initiative started to make this clear to the commercial world, and very slowly, commercial vendors are starting to see the point. While lots of academics and technical people have already been convinced for 20 years now that this is the way to go, commercial vendors needed applications like the Internet to make them realize they can profit from Open Source.

Linux Community Now Linux provides more than the operating system: there is an entire infrastructure supporting the chain of effort of creating an operating system, of making and testing programs for it, of bringing everything to the users, of supplying maintenance, updates and support and customizations, etcetera. Today, Linux is ready to accept the challenge o a fast-changing world.

Linux Today Linux is well-known as a stable and reliable platform, providing database and trading services for companies like Amazon, the well- known online bookshop, US Post Office, the German army and many others. Especially Internet providers and Internet service providers have grown fond of Linux as firewall, proxy- and web server, and you will find a Linux box within reach of every UNIX system administrator who appreciates a comfortable management station.

Linux Today Clusters of Linux machines are used in the creation of movies such as "Titanic", "Shrek" and others. In post offices, they are the nerve centers that route mail and in large search engine, clusters are used to perform internet searches. These are only a few of the thousands of heavy-duty jobs that Linux is performing day-to-day across the world.

Part 3 Overview of Linux Features

Multitasking OS Every application has their own memory space so, –Things that die don’t take other programs with it –Can’t hog the memory unless instructed to do so The kernel monitors everything

Multi-user One computer can serve the needs of many users at once Each user can have different settings for the same application Standard Unix/Linux concept

Linux File System Many different types of file systems can be used Automatic defragmentation Can read other, non-Linux, file systems (FAT and NTFS for starters)

Stability Because everything is separated, a reboot or a freeze caused by a program is almost non-existant Linux computers have uptimes that stretch many months and even years!

Programmable shells Linux is the most flexible operating system available whereby programmers can write their own programs inside Linux shells Linux is device independence as well as Unix Programmers around the world developed the drivers of many hardware available for Linux.

Interface Since no one company controls everything, there are numerous desktop environments Each is just as interface to the X window system tools The two most popular are KDE and GNOME Most window managers have features like multiple desktops per user

KDE

GNOME

Part 4 Linux Command Line & File Structure

Linux command Linux is case sensitive i.e. WHO is not same as who Linux shell is a command program to communicate with a computer Shell interprets the command that you enter on keyboards Shell commands can be used to automate various programming tasks

Linux command Usually short and cryptic like –vi or rm (remove) Commands may also have modifiers for advance options like: –“ls –l” and “mv –R” are different than “ls” or “mv” respectively

Some Linux commands ls, Give a listing of the current directory. Try also ls -l cp, Copy file from source to destination mv, Move file from source to destination. If both are the same directory, the file is renamed vi, Edit a file. vi is one of the most powerful text editors chmod, Change file permissions mkdir, rmdir Make/Remove a directory cd, Change directory rm, Remove a file. Can also remove directory tree man ls, Get help for ls. All commands have help

Help on command line man : Type man and the name of a command to read the manual page for that command. e.g. “man ls” apropos: gives a list of commands that contain a given keyword in their main page header: e.g. “apropos ls”

Wildcard You can substitute the * as a wildcard symbol for any number of characters in any filename. If you type just * after a command, it stands for all files in the current directory: - lpr * will print all files You can mix the * with other characters to form a search pattern: – ls a*.txt will list all files that start with “a” and end in “.txt” The “ ? ” wildcard stands for any single character: - cp draft?.doc will copy draft1.doc, draft2.doc, draftb.doc, etc.

ls The ls command is used to list the contents of a directory. It is probably the most commonly used Linux command. It can be used in a number of different ways. Here are some examples: –ls – list the files in the working directory –ls /bin – list the files in the /bin directory (or any other directory you want to specify) –ls –l – list the files in the working directory in long format –ls –l /etc /bin – list the files in the /bin directory and the /etc directory in long format –ls –la – list all files (even ones with names beginning with a period character, which are normally hidden) in the parent of the working directory in long format

cp The cp program copies files and directories. Examples: me]$ cp file1 file2 – copy a single file me]$ cp file1 file2 file3 directory – copy multiple files to a different directory

mv The mv command performs two different functions depending on how it is used. It will either move one or more files to a different directory, or it will rename a file or directory. Examples: me]$ mv file1 file2 – rename a file me]$ mv file1 file2 file3 directory – move files to a different directory

rm AND mkdir rm The rm command deletes (removes) files. Example: me]$ rm file rmdir The rmdir command deletes directories. Example: me]$ rmdir directory mkdir The mkdir command is used to create directories. Example: me]$ mkdir directory

Linux Users Root –Controls all system files –Only user that can do “anything”, even look at/delete another users’ files –Usually the only user that can install most programs Normal users –Each has a “home” directory –Files are separated from other users –Cannot edit system data/configuration –Often can’t even see system data

Basic File Structure Hard disk is divided into partitions –Usually a minimum of 2: / (root) and /home –Idea is to keep user data and system data separated to prevent problems Users: 2 minimum –Super user (root) –At least one “regular” user

File Permission Every file and directory has three sets of permissions –Read (r) – can read the file –Write (w) – can write, change and delete the file –Execute (x) – an executable script/file Permissions can then be set for three different groups –User – the person that owns (created) the file –Group – the group the user belongs to –Others – everyone else

File Permission

chmod