Linux System Fundamentals Lesson 1: Installation & Basics

Sadia Bashir

Contents

Setting up Ubuntu 16.04 LTS Server/Desktop in a virtual machine

What is Kernel?

What is CLI?

What is root (superuser)?

Understanding and using “sudo”

Understanding and using basic commands

What is Linux Home Directory?

Using auto-complete feature

What are man pages?

Setting up Ubuntu 16.04 LTS Server/Desktop in a virtual machine

Installing Oracle VirtualBox

Setting up Ubuntu Server 16.04 LTS Server/Desktop in a virtual machine

Installing putty

Log into a Linux server and run simple updates and upgradation

What is Kernel?

It is the core of a computer operating system that provides basic services for all other parts of the operating system.

What is command-line?

Command-line interface - CLI : tool which is used to type text commands to perform specific tasks

Shell : The application or user interface that accepts user’s typed responses and displays the data on the screen

What is root (superuser)?

A special user account used for system administration - has control over the entire Linux system

the user with a user identifier (UID) of zero

the only user account with permission to modify the root directory of a Unix system

It is capable of doing what normal users can’t, such as, changing ownership of files, adding or removing files from system directories, installing new packages and many others.

“/” or “root” directory is different from “root” user.

Understanding and using “sudo” (super user do)

sudo is a program for Unix-like computer operating systems that allow users to run programs with the security privileges of another user, by default the superuser.

It prompts for personal password and confirms given request to execute a command by checking a file, called sudoers, which the system administrator configures.

Usage: - sudo su

- su -

- sudo apt-get update

- sudo apt-get upgrade

- sudo apt-get update &sudo apt-get upgrade

Switch to “root” user

Use “sudo” to install packages

Understanding and using “sudo” (contd…)

Understanding and using basic commands What is Linux Home directory?

Check present working directory - pwd

Switch directories - cd

View directory contents - ls

View file contents - cat

List logged-in users:- users - who - whoami- last

Check ubuntu server version - lsb_release

Search for files – locate

Clear the terminal – clear

Show command history - history

Using auto-complete feature

What are man pages?

What is Linux Home Directory?

Linux is a multi-user operating system, which means that more than one users can access the OS at the same time. Each user is assigned a directory where he/she can store their personal files. This directory is known as a user's home directory.

Each user has complete control over his home directory as well as all its sub-directories. He/She can freely perform operations like: - create and delete files/directories

- install programs, and more, inside their home directory

a user’s home directory has the same name as their login name.

home directories are found under the home directory (/home).

Checking Present Working Directory (pwd)

Whenever a user opens up a command line shell in Linux, it starts at the user’s home directory by default. This is user’s present working directory, which changes when he switches to some other directory.

pwd command is used to check the complete path of user’s present working directory at any point of time.

Switch directories (cd)

command to navigate through the Linux filesystem

this command requires either a directory name or its complete path depending upon where the directory is present

Usage:- cd /path/to/ or

- cd directory_name

- cd ..

- cd -

- cd ~

- cd /Switch immediately to home directory regardless of what present working directory is.

Switch back and forth between directories (toggling)

Switch to parent directory (single dot represents current directory)

Switch to root directory

View directory contents – ls

lists the contents of a directory. the output of the ls command is color coded. different colors represent different types of files, making it easy to visually

identify them. Color codes:

- Blue (Directories),- White (Text files),- Red (Archives),- Cyan (Links),-Green (Executables), - Pink (Images),- Yellow (Device Files)

View directory contents – ls (contd…)

Usage- ls directoryName/directoryPath

-Options: -l : detailed listing

-a : show hidden files

-t : sort list based on timestamp

-S : sort list by file size

-r : reverse the sorting

-d : list directories only, not their contents

-h : print human readable sizes (e.g., 1K 234M 2G)

use combination : -lShrt

View File Contents - cat

Prints out file’s contents on standard output

Command: cat FILE1.txt

cat FILE1.txt FILE2.txt

cat FILE1.txt - FILE2.txt : Output FILE1's contents, take input from user, and then output FILE2's contents

Options: -E : display $ at end of each line

-n : number all output lines

List logged-in users

Commands to check the complete list of logged in users either current or all those attempts which have been made to connect user’s machine by any user and the status of connection

Users : prints user names of currently logged in users

Last –a : displays a list of all users logged in (and out) since the OS is installed

Who : shows currently logged in users with time details

Whoami : prints the user name associated with the current effective user ID

Show command history – (history)

history command shows a list of all the recently used commands

up/down arrows are used to loop through them

The Ctrl+R shortcut key will start a search mode where the first few characters of a command are typed to search through recent history

Using auto-complete feature

tab key is used to auto complete long names and paths easily

In case of similar initial names, shell displays all the names that it can use for auto completion

What are man pages?

To learn more about Linux commands, users can head over to the respective man (or Manual) pages that come preinstalled with Linux.

To open a man page, man command followed by the command name is run.