UNIT 1

● Introduction to operating sytem , kernel and shell● FLOSS/FOSS ● Linux features & Different Distros ● Linux v/s Windows

OPERATING SYSTEM● To do anything useful with a computer, we need to run

software, or programs, on the hardware. Two types of software exists --

● APPLICATION SOFTWARE -- for each different application we need different application program like for word-processing we need the MS-Word etc.

● SYSTEM SOFTWARE – is a program or collection of programs that acts as an intermediary between a user of a computer and the computer hardware. It makes the hardware and software work together and different hardware to communicate with each other . Different types of OS --

● Windows , Unix , Linux , Sun Solaris , Multics ,MacOS etc

ABSTRACT VIEW OF OF COMPUTER SYSTEM

Kernel and Shell● Operating system can be further subdivided into 2 parts.

While the system is operational a program is constantly running known as KERNEL. It forms the core of any operating system

● The other part of operating system is shell which is the interface between user and system itself. It allows the user to instruct the machine and to run programs. A shell communicates with the kernel, but keeps the user at arm’s length from it. A shell only active when somebody is using the system while kernel is always active. Todays different type of shell exists depending on the ideas of different developers who created them .

● Sh --Bourne shell (first shell named after its creator)

bash – Bourne again shell

● Ksh (korn shell)● Csh ( c shell)● Zsh and tcsh (pronounced – teesh)

KERNEL

HARDWARE

SHELL

● OPEN SOURCE : software and source code available to all

● The freedom to distribute software and source code● The ability to modify and create derived works● Integrity of author's code

● GNU : In 1984, Richard M. Stallman started the GNU project (www.gnu.org), recursively named by the phrase GNU is Not UNIX.The GNU project aimed at creating a UNIX-like open source operating system free from regulations preventing it from being modified and redistributed.GNU worked on GNU Hurd OS and also build several open source compilers and libraries but Its aim of Open source Operating system was achieved in 1991 with the birth of LINUX KERNEL

● LINUX :Linus Torvalds , a student at the University of Helsinki, created the first version of “Linux” in August 1991. Released as an open-source software under the Free Software Foundation's GNU General Public License (GPL)

FLOSS – FREE/LIBRE OPEN SOURCE SOFTWARE

● A company can charge money for products that include Linux, as long as the source code is made available. The GPL allows people to distribute (and charge for) their own versions of free software.

● According to the Free Software Foundation, the "free" in free software refers to freedom or liberty, not price.

● Linux refers to the “ kernel or core ” of the operating system. Combining Linux with a set of open-source GNU programs from the Free Software Foundation turns it into what most people know as Linux ”forming both the full operating system and the core of most Linux distributions”.

● Linux Distributions are built on the versions of Linux kernel, GNU programs, and other tools that are offered by different companies, organizations, or individuals. There are over 600 Distro available today. (www.distrowatch.com)

Categorise as the commercial-backed distro like – Fedora(Redhat) ,openSUSE(novell),Ubuntu(Canonical Ltd)

● And entirely community-driven distributions, such as Debian , Centos and Gentoo.

● While different Linux systems will add different logos, choose some different soft-ware components to include, and have different ways of installing and configuring, one can easily move from one distro to another because --

● include the same open source projects , like apache , samba or mail servers etc

● Linux Standard Base Specification (www.linuxbase.com) has as one of its primary goals to ensure that applications written for one Linux system will work on other systems.

● A shell is a shell on all the different distros.

TUX IS LINUX OFFICIAL MASCOT->

LINUX FEATURES

● It's free

● It's Open Source

● It's Modular --Commercial Operating Systems normally get installed as a complete unit. One cannot, for example, install them without their Graphical User Interface, or without its printing support -- install everything or nothing

● It’s got More Choices – Kde, GNOME ,lxde,xfce

● It's portable – we can run on atmiga , arm arch , embedded systems, Machintosh, Sun Sparc, HP, Silicon Graphics , Motorola etc.

● Its comes loaded with softwares like web , ftp , samba and office suite etc on the distro CD.

● Its stable -- Linux is rock-solid. Every application runs independently of all others – if one crashes, it crashes alone

● Multiple OS’ s on a PC -- Linux can read Windows' files - it supports the FAT and FAT32 file system’s, and NTFS. The opposite, however, is not possible.

● Linux is Multi User -- several users can log-on simultaneously. This means you can share the same program installation among various users.

● Linux is Multi Vendo -- means that by choosing Linux, you choose to depend on a set of (more than 600) Linux distributors in the world, plus the open source community. Not dependent on a unique vendor. It is also safer, prices-if any are driven by the market, not by monopoly.

Red Hat Distributions● Red Hat Enterprise Linux---

● Stable, thoroughly tested software

● Professional support services with 24x7 coverage plans.

● Centralized management tools for large networks

● Version available started from 2.1, 3.0, 4.0, 5.0 now 6.0

● Support many processor architectures – Intel x86 compatible, Intel Titanium 2, AMD64, IBM PowerPC

● The Fedora Project---

● More, newer applications

● Community supported (no official Red Hat support)

● For personal systems

LINUX VS WINDOWS● Open source Closed Source

● Can modify & Redistribute Cant modify & Redistribute

● Covers the 70 % share of Covers the 23% share webservers webservers

● 91 % of supercomputer run 1% of supercompter share run on

linux (top 14 runs linux only) windows

● Filesystem – ext2,ext3,ext4 Filesystem - NTFS, FAT, ISO 9660reiserfs ,FAT, NTFS, NFS, UDF UDF ,HFS ISO 9660 , JFS,XFS

● Linux installers will automatically Windows installers will overwrite the detect and set up other operating MBR , thus rendering non-Windows systems for dual/multiple boot partition unusable with Linux

● Linux Kernel is modular , drivers Windows Kernel is Monolithic and all are loaded dynamically whenever drivers are loaded at boot time thus required thus, reducing boot time boot time is more

● Linux doesnt require defrag- Windows partition require mentation. Defragmentation.

● Linux application are installed Windows rely on windows installer with package manager such as to install third party applications. apt or yum etc which ensure all dependencies are met.

● As of 2006 more than 800 pieces As of 2009 more than 2 million of malware had been detected malware have been detected for windows

● Linux stores configuration in plain Windows Database of configuration text file is Registry

● “/” is the head of system file “c:\” is generally where we get storage system files

● “/home” stores the user files and “Document & Settings” stores the /root stores the admin files user files and admin files also

● “/bin” stores the normal binaries “Program files” stores the binaries “/sbin” --system binaries “/usr/bin” -- user binaries

● “/etc” stores the config files “windows/system32” stores the config files

● “/tmp” stores the temporary files “%temp%” stores temporary files

● “SWAP –memory overcommit “ Virutal Memory” upto 4 GB --> 2XRAM 1.5 Of RAM 6 GB --> 1X RAM 8 GB --> .5X RAM

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EXERCISE

● What is GPL /GNU Licensing ?● What are differences b/w linux and unix● Study Linux Distro family● Study ext3 , ext4 and other linux filesystem

● References --● http://en.wikipedia.org● http://www.nrcfoss.au-kbc.org.in● http://www.distrowatch.com● http://encyclopedia.thefreedictionary.com● RHCE Red Hat Certified Engineer Linux Study

Guide by Michael Jang