Introduction to UNIX

DAY -1

What Is an Operating System ?

Computer hardware & software are so complex that every computer requires a program to manage its resources.

The program is known as Operating System.

A list of instructions for the computer to follow is called as a program.

DEFINITION:-

Operating System is a collection of programs that coordinates the operation of computer hardware and software.

OPERATING SYSTEM

What does an Operating System Do?

To manage the computers hardware resources effectively

To make it easy for you to use the computer system.

To manage how programs are run, how data is stored & so on.

Examples: UNIX (Solaris one of the Flavor) , Linux,Windows NT,95/98/2000, DOS

What it does?

History of UNIX

What is Unix ?

Unix is an Operating System –a program, which operates the computers on your behalf.

UNIX stands for UNiplexed Information and Computing System. (It was originally spelled "UNICS.")

UNIX origin is MULTICS Multiplexed Information & Computing ServiceInvented in 1969

–by Ken Thompson, Dennis Ritchie–@ Bell Labs, the research arm of AT & T–Originally written in assembly language–UNIX is written in 80 percent of C language and 20 percent assembly language.

History of UNIX

Features of UNIX

Multitasking

Multi-User

Portable

Security

High Availability

Strong Cluster support

UNIX Architecture

Shells

Borne ShellBorne Shell Korn ShellKorn ShellC Shell

User

Kernel

Hardware

Unix Architecture

SHELL

Definition:

Shell is the interface between the user and the kernel.

Services provided by the shell• It interprets all the commands to the kernel • The kernel after processing the commands gives back to the

shell.

KERNEL

Definition: A set of functions that make up an OS, used to provide an application interface between programs and

physical devices.

Services provided by the kernel

controlling execution of processes.

scheduling processes fairly for execution on the cpu.

allocating memory for an executing process.

Flavors of UNIX

VENDOR O.S

SCO SCO-UNIX

IBM AIX

UNIX + HP HP-UX

SGI IRIX

SUN Solaris

Open Source LINUX

Flavors of UNIX

System Administration

• System administration is the job of managing, maintaining and operating a computer or a network of computers.

• System administrator usually – install new services– maintain existing ones– intervene whenever environmental or human factors

interface with normal operations

System Administration

Essential tasks

• The task of a system administrator are varied and diverse.– adding and removing users,– adding and removing hardware,– performing backups– installing new software– monitoring the system– maintaining hardware– maintaining documentation– monitoring security– helping users