Open source Operating System: Based on UNIX

has different flovours, can be configured in so many ways according to different purpose

ARCHLinux - used by developers

CentOS - used by enterprised versions and web servers - based on REDHAT

ubuntu - based on DEBIAN Linux - famous for Desktop version

Kalilinux - for hackers

Redhat linux - enterprise version

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file based

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architecture

application - UI

shell

kernel - interface between application and hardware

hardware - RAM, CPU, HARDWARE DRIVE

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shell - takes input in human readable format and gives to kernel in binary code

1st shell - sh

bash is more popular now

types of shell - bash #! /bin/bash - to tell linux to execute in bash interpreter

Cshell, Korn shell, tsch shell

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File structure in linux

whereis <File name> - to find particular file in linux

usr/local/bin so that we can access anything here from any directory