Unix Overview

 History of Unix

  • In 1970, Dennis Ritchie and Ken Thompson's started devloping Unix in AT&T.
  • 1972 they developed unix using 'C'.
  • 1975 they spreads outside. (With free license and source code)
  • Its an open source.
  • Different flavours available at free of costs.
  • Unix is case sensitive.
  • Production versions only available in Unix.

Linux

  • Linux is a light weight version of Unix.
  • Linux derived/Inspired from Unix.
  • Linux is an open source but we have to get BSD license for using UNIX. Unix is not a open source. Also GNU license need for installing Unix.
    • BSD (Berkeley Software Distribution)
    • GNU (GNU General Public License)
  • Linux is journal purpose computer operating system.
  • Originally build by Linus Torvalds and released in 1991.
  • Linux is defined by its Kernal which is the core component of the system. It interact computer hardware to software for work.
  • Here the software and OS will be free for free of cost and freely modifiable. (GNU General Public License)
  • Linux is popular from many different applications, Bcoz 100's of variations we can see in this edition. 
    • Ex: From server operating system, super computer system, mobile phones, androids, iphone.
  • Major Distibution based on original OS : Arch, Debian, Red Hat and Slackware, etc. (Debian and Red Hat are popular.)
  • Most of the companies using Debian and Red Hat.
  • Debian  categories : Linux Mint, Ubuntu, Elementary OS, and Kali Linux.
  • Red Hat categories : centOS, Fedora, Red Hat Enterprise Linux.
  • Bash Shell - Available almost everywhere.

Unix Architecture






Kernel

  • Kernal is a heart of system or core of the OS.
  • Will allocate time and memory management.

SHELL

  • SHELL is acting like an interface of users and kernal.
  • Outer layer of OS.
  • Interact with user.
  • Sent request to kernal.
  • Return result to user.
SHELL Variations,

    sh : Thomson Shell (1971)
    sh : Bourne Shell (1977)
    csh : C Shell (1979)
    ksh : Korn Shell (1982)
    bash : Bourne again Shell (1987)
    zsh : Z shell (1990)
  • Thomson shell completely replaced by Bourne Shell on 1977.

OS & Device Category

  • Open Source : BBD, Linux
  • Closed Source : Sun Solaris (Sun micro system), AIX (IBM), HP/UX, Oracle Unix(Oracle)
  • Mixed Source : MAC OS X (Also available in all categories)
Mobile device OS
  • Android, IPhone, IPad are Developed using Unix.
MAC OS X

Its combination of BSD + NeXTSTEP + Apple Code and we can call it as Darwin OS.
  • NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD.
  • Darwin is the core Unix operating system of macOS, iOS, watchOS, tvOS, iPadOS and bridgeOS. It previously existed as an independent open-source operating system, first released by Apple Inc. in 2000.

Working with files and directories

Use below Naming rules,
  • Max of 255 char.
  • Avoid /, \, *, &, $, |, <, > and most other symbol. (Bcoz most of the time it has some functionality.)
  • Use a-z, A-Z, 0-9, period, underscore, hypens.
  • Typically lowercase. (MyFile and myfile would be different)
  • Underscores are better than spaces.
  • File ending (.txt, .png, .html, etc) not required but helpful.

Unix File system

/               Root
/bin          Binaries, Programs
/sbin        System binaries, System Programs.
/dev         Devices, hard drives, key boards, mouse, etc.
/etc          system configuration's.
/home      User home directories.
/Lib         Libraries of code.
/tmp        temporary files.
/var         various, mostly files the system user.
/usr/etc    User Pgm's, tools and libraries (not files).

Linux versions Info


cat /etc/*-release
  • It will display the information of your version using.
  •   For MAC, this command wont work.
uname -a 
  • For MAC, name of Macro.
free -h
  • -h means human readable number format. It will display how much memory we have totally, used, free details.
cat /proc/cpuinfo
  • It will give the details of processor, model, cpu informations.
echo $0
  • Used to view SHELL model. (-bash)

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