Unix/Linux get started Lesson 01

 

Unix/Linux get started

What is Unix ?

The Unix operating system is a set of programs that act as a link between the computer and the user.

The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or the kernel.

Unix Architecture

·         Kernel − The kernel is the heart of the operating system. It interacts with the hardware and most of the tasks like memory management, task scheduling and file management.

·         Shell − The shell is the utility that processes your requests. When you type in a command at your terminal, the shell interprets the command and calls the program that you want. The shell uses standard syntax for all commands. C Shell, Bourne Shell and Korn Shell are the most famous shells which are available with most of the Unix variants.

·         Commands and Utilities − There are various commands and utilities which you can make use of in your day to day activities. cp, mv, cat and grep, etc. are few examples of commands and utilities. There are over 250 standard commands plus numerous others provided through 3^rd party software. All the commands come along with various options.

·         Files and Directories − All the data of Unix is organized into files. All files are then organized into directories. These directories are further organized into a tree-like structure called the filesystem.

 

Lets see how we log in to Linux:

 

login : root

root's password:

Last login: Mon Feb  5 09:58:32 2024 from 192.168.15.60

Change Password

#passwd

Changing password for root
(current) Unix password:******

New UNIX password:*******

Listing Directories and Files

All data in Unix is organized into files. All files are organized into directories. These directories are organized into a tree-like structure called the filesystem.

You can use the ls command to list out all the files or directories available in a directory. Following is the example of using ls command with -l option.

Who Are You?

Who is Logged in?

System Shutdown

The most consistent way to shut down a Unix system properly via the command line is to use one of the following commands −

1 halt Brings the system down immediately 2 init 0 Powers off the system using predefined scripts to synchronize and clean up the system prior to shutting down 3 init 6 Reboots the system by shutting it down completely and then restarting it 4 poweroff Shuts down the system by powering off 5 reboot Reboots the system 6 shutdown Shuts down the system