1 Intro, Linux system Architecture, Features, File system Structure and applications.pptx

linux

1. Linux Operating system & Features

2. An operating system is an interface between the user of a computer and the computer hardware. It is a collection of software that manages computer hardware resources and offers common services for programs of the computer. The main purpose of an OS is to afford an environment in which a user can execute a program in an efficient or convenient manner.

3. Operating systems are categorized into six types based on the types of computers they control such as single user single task operating systems real time operating systems single user multitasking operating systems multiuser operating systems distributed operating system embedded  operating systems

4. The typical services that an operating system provides include: a task scheduler memory manager disk manager network manager Other I/O services and Security manager.

5. In 1987, MINIX, a Unix-like system intended for academic use, was released by Andrew S. Tanenbaum to exemplify the principles conveyed in his textbook,  Operating Systems: Design and Implementation . 

6. History Of Linux – How Did Linux Start And Who Created Linux?

7. History Of Linux – How Did Linux Start And Who Created Linux? Linux, a freely distributable version of  UNIX  is developed by  Linus Torvalds . Linux is one of the most popular operating systems to use for development by programmers. This tutorial will take a deep dive into the history of Linux.

8. The beginning of the UNIX project The inspiration for UNIX came from the  Multics  project at the Bell Laboratories. This project aimed at building a multi-user operating system with single-level storage, dynamic linking, and a hierarchical file system. The project was in collaboration with AT&T. Later, however, this project came to an end in 1969 due to financial issues.

9. Even after the discontinuation of the project, two scientists  Ken Thompson and Dennis Ritchie  continued working with the idea. They later decided to rewrite the operating system in  C language . This was named  ‘UNIX ‘. UNIX quickly gained popularity and by the 80s, major organizations like IBM and HP were creating their own UNIX systems. The reason for UNIX gaining popularity was its availability and portability .

10. The beginning of the GNU project In the year 1983,  Richard Stallman  was working along with the  Free Software Foundation(FSF ) to come up with the first free UNIX-like operating system. This was called the GNU project. During this project, Richard came up with ‘ Hurd ‘ which is the GNU Kernel. GNU was later used by Linus Torvalds for developing Linux. GNU’s short for “ GNU’s not Unix! “. It’s a recursive acronym, as there’s no real full-form of the word GNU.

11. Who developed Linux – About Linus Torvalds Linus Benedict Torvalds  was born on  28 December 1969  in Helsinki, capital of Finland. He studied at the University of Helsinki in Finland. This is where he started working on a project for ‘fun’. This project later shaped into what we today know as Linux. Torvalds began programming at the age of 10 on his grandfather’s Commodore VIC-20. He created Linux as a part of his Master’s thesis titled,  ‘Linux: A Portable Operating System’ . He was just 21 years old when he started working on Linux.

12. Torvalds announced Linux to the world on  25 August 1991.  He wrote about Linux on a Usenet newsgroup called “comp.os.minix”.  The message he posted was:

13. Torvalds only developed the Linux Kernel. The Linux operating system is a collaboration between millions of developers all around the world, involving the GNU Project, the  Linux kernel development team  (headed by Torvalds), and others. The first release of Linux The first prototypes of Linux were publicly released in 1991. The first version(1.0) came out in  1994.

14. Mascot Design for Linux The official mascot for Linux, a penguin was announced in 1996. The penguin was called  ‘TUX’.

15. Linux Distributions Over the years, several distributions of Linux have come out. Some of the popular ones are Ubuntu Linux Mint Debian Fedora Red Hat Enterprise Linux CentOS .

16. Story of Linux: https://www.youtube.com/watch?v=5ocq6_3-nEw&t=34s How linux built: https://www.youtube.com/watch?v=yVpbFMhOAwE

17. In the year 1991, Linux was introduced by a Finland student Linus Torvalds. Hewlett Packard UniX(HP-UX) 8.0 was released. In the year 1992, Hewlett Packard 9.0 was released. In the year 1993, NetBSD 0.8 and FreeBSD 1.0 released. In the year 1994, Red Hat Linux was introduced, Caldera was founded by Bryan Sparks and Ransom Love and NetBSD1.0 Released. In the year 1995, FreeBSD 2.0 and HP UX 10.0 was released. In the year 1996, K Desktop Environment was developed by Matthias Ettrich. In the year 1997, HP-UX 11.0 was released. In the year 1998, the fifth generation of SGI Unix i.e IRIX 6.5 , Sun Solaris 7 operating system and Free BSD 3.0 was released. In the year 2000, the agreement of Caldera Systems with SCO server software division and the professional services division was announced. In the year 2001, Linus Torvalds released the Linux 2.4 version source code. In the year 2001, Microsoft filed a trademark suit against Lindows.com In the year 2004, Lindows name was changed to Linspire. In the year 2004, the first release of Ubuntu was released. In the year 2005, The project, openSUSE began a free distribution from Novell’s community. In the year 2006, Oracle released its own distribution of Red Hat. In the year 2007, Dell started distributing laptops with Ubuntu pre installed in it. In the year 2011, Linux kernel 3.0 version was released. In the year 2013,  Googles Linux based Android claimed 75% of the smartphone market share, in terms of the number of phones shipped. In the year 2014, Ubuntu claimed 22,000,000 users

18. Linux System Architecture

19. The types of Kernels are as follows: Monolithic Kernel Micro kernels

20. The kernel is the core part of the operating system, which is  responsible for all the major activities of the LINUX operating system. This operating system consists of different modules and interacts directly with the underlying hardware. The kernel offers the required abstraction to hide  application programs or low-level hardware details to the system.

21. A Monolithic kernel is an OS architecture where the entire operating system (which includes the device drivers, file system, and the application IPC) is working in kernel space. Monolithic kernels are able to dynamically load (and unload) executable modules at runtime. Examples of operating systems that use a monolithic kernel are - Linux, BSDs (FreeBSD, OpenBSD, NetBSD), Solaris, OS-9, AIX, HP-UX, DOS, Microsoft Windows (95,98,Me), OpenVMS, XTS-400 etc.

22. Where as in a Microkernel architecture, the core functionality is isolated from system services and device drivers. Examples of operating systems that use a microkernel are - QNX, Integrity, PikeOS, Symbian, L4Linux, Singularity, K42, Mac OS X, HURD, Minix, and Coyotos.

23. System libraries are special functions, that are used to implement the functionality of the operating system and do not require code access rights of kernel modules. System Utility programs are liable to do individual, and specialized-level tasks. Hardware layer of the LINUX operating system consists of peripheral devices such as RAM, HDD, CPU.

24. The shell is an interface between the user and the kernel, and it affords services of the kernel. It takes commands from the user and executes kernel’s functions. The Shell is present in different types of operating systems, which are classified into two types: command line shells and graphical shells.

25. The command line shells provide a command line interface, while the graphical line shells provide a graphical user interface. Though both shells perform operations, but the graphical user interface shells perform slower than the command line interface shells .

26. Shell Types Sh:The Bourne shell, called "sh," is one of the original shells, developed for Unix computers by Stephen Bourne at AT&T's Bell Labs in 1977. Its long history of use means many software developers are familiar with it. It offers features such as input and output redirection, shell scripting with string and integer variables, and condition testing and looping.

27. Bash:The popularity of sh motivated programmers to develop a shell that was compatible with it, but with several enhancements. Linux systems still offer the sh shell, but "bash" -- the "Bourne-again Shell," based on sh -- has become the new default standard. One attractive feature of bash is its ability to run sh shell scripts unchanged.

28. csh and tcsh ksh

29. Features of Linux Operating System Portable Multi user Multi programming security shell Hierarchical file system Open source

30. Portable:  Linux operating system can work on different types of hardware as well as Linux kernel supports the installation of any kind of hardware platform.

31. Open Source:  Source code of LINUX operating system is freely available and,  to enhance the ability of the LINUX operating system, many teams work in collaboration.

32. Multiuser:  Linux operating system is a multiuser system, which means, multiple users can access the system resources like RAM, Memory or Application programs at the same time.

33. Multiprogramming:  Linux operating system is a multiprogramming system, which means multiple applications can run at the same time.

34. Hierarchical File System:  Linux operating system affords a standard file structure in which system files or user files are arranged. Shell:  Linux operating system offers  a special interpreter program, that  can be used to execute commands of the OS. It can be used to do several types of operations like call application programs, and so on.

35. Security:  Linux operating system offers user security systems using authentication features like encryption of data or password protection or  controlled access to particular files.

36. Applications of Linux Operating System Nowadays, Linux is a multi billion dollar industry. Thousands of companies and governments around the world are using Linux OS due to affordability, lower licensing fee  and time and money. Linux is used in a number of electronic devices, which are available for consumers worldwide. The list of some of popular Linux based electronic devices includes:

37. Dell Inspiron Mini 9 and 12 Garmin Nuvi 860, 880, and 5000 Google Android Dev Phone 1 HP Mini 1000 Lenovo IdeaPad S9 Motorola MotoRokr EM35 Phone One Laptop Per Child XO2 Sony Bravia Television Sony Reader TiVo Digital Video Recorder Volvo In-Car Navigation System Yamaha Motif Keyboard

38. Therefore, this is all about the Linux operating system, history, architecture, features and applications of the Linux operating system 

39.   Linux Directory Structure (File System Structure)

40. / – Root Every single file and directory starts from the root directory. Only root user has write privilege under this directory.

41. /bin – User Binaries Contains binary executables. Common linux commands you need to use in single-user modes are located under this directory. Commands used by all the users of the system are located here. For example: ps, ls, ping, grep, cp.

42. /sbin – System Binaries Just like /bin, /sbin also contains binary executables. But, the linux commands located under this directory are used typically by system aministrator, for system maintenance purpose. For example: iptables, reboot, fdisk, ifconfig, swapon

43. /etc – Configuration Files Contains configuration files required by all programs. /etc/passwd The passwd file contains the essential information for each user /etc/shadow file contains password This also contains startup and shutdown shell scripts used to start/stop individual programs.

44. /dev – Device Files Linux exposes devices as files, and the /dev directory contains a number of special files that represent devices. These are not actual files as we know them, but they appear as files  This directory also contains pseudo-devices, which are virtual devices that don’t actually correspond to hardware.

45. /proc – Process Information Contains information about system process. This is a pseudo filesystem contains information about running process. For example: /proc/{pid} directory contains information about the process with that particular pid. This is a virtual filesystem with text information about system resources. For example: /proc/uptime

46. /var – Variable Files var stands for variable files. Content of the files that are expected to grow can be found under this directory. This includes — system log files (/var/log); packages and database files (/var/lib); emails (/var/mail); print queues (/var/spool); lock files (/var/lock); temp files needed across reboots (/var/tmp);

47. /tmp – Temporary Files Directory that contains temporary files created by system and users. Files under this directory are deleted when system is rebooted.

48. /usr – User Programs Contains binaries, libraries, documentation, and source-code for second level programs. /usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look under /usr/bin. For example: awk, cc, less, scp /usr/sbin contains binary files for system administrators. If you can’t find a system binary under /sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel /usr/lib contains libraries for /usr/bin and /usr/sbin /usr/local contains users programs that you install from source. For example, when you install apache from source, it goes under /usr/local/apache2

49. /home – Home Directories Home directories for all users to store their personal files. For example: /home/john, /home/nikita

50.   /boot – Boot Loader Files Contains boot loader related files. Kernel initrd, vmlinux, grub files are located under /boot For example: initrd.img-2.6.32-24-generic, vmlinuz-2.6.32-24-generic

51. lib – System Libraries Contains library files that supports the binaries located under /bin and /sbin

52. /opt – Optional add-on Applications opt stands for optional. Contains add-on applications from individual vendors. add-on applications should be installed under either /opt/ or /opt/ sub-directory.

53. /mnt – Mount Directory Temporary mount directory where sysadmins can mount filesystems. Historically speaking, the /mnt directory is where system administrators mounted temporary file systems while using them. For example, if you’re mounting a Windows partition to perform some file recovery operations, you might mount it at /mnt/windows. However, you can mount other file systems anywhere on the system.

54. /media – Removable Media Devices Temporary mount directory for removable devices. For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD writer /srv – Service Data srv stands for service. The /srv directory contains “data for services provided by the system.” If you were using the Apache HTTP server to serve a website, you’d likely store your website’s files in a directory inside the /srv directory.