UNDERS TANDING
LINUX
C ONCEP TS
What is Operating
System?
As per Wikipedia
An operating system is system software that manages computer hardware and
software resources, and provides common services for computer programs
In simple words
An operating system (OS) is software that acts as a middleman or a bridge between
computer hardware and the computer user. It provides a user interface and controls
the computer hardware so that software can function
Types of Operating Systems:
1. Desktop Operating Systems, e.g., Microsoft Windows, macOS, and Linux such as Ubuntu
2. Server Operating Systems, e.g., Windows Server, Linux distributions like CentOS, Red Hat Enterprise
Linux
3. Mobile Operating Systems, e.g., Android, iOS, Windows Mobile
4. Embedded Operating Systems used in devices like routers, smart TVs, automobiles, home appliances
etc.
5. Real-Time Operating Systems (RTOS) used in critical systems like medical equipment, car ECUs,
aerospace,
defense, network firewalls, home security system etc.
WHAT IS LINUX?
Linux is an Operating System which sits in the
middle of your hardware and users
Unix vs. Linux
• Unix was first developed for multi-user and multi-tasking in mid-1970 in Bell Labs
by ATT, GE and Massachusetts institute of Technology
• Then born Linux in 1991 by Linus Torvalds
• Linux is mostly free
• Linux is open source
• Unix is mostly used by Sun as Solaris, HP-UX, AIX etc.
• Linux is used by many developers community or companies (Redhat, CentOS,
Debian) etc.
• Unix comparatively supports very fewer File systems
• Linux can be installed on a wide variety of computer hardware, ranging from
mobile phones, tablets, video game consoles, to mainframes and supercomputers.
11 4 LINUX
C OMMANDS
LINUX V S.
WINDOWS
LINUX
DIS TRIBUTIONS
Redhat
Linux Users
• US Government and Agencies (National, State, Federal and International)
• NASA
• Health Care
• The Bullet Trains in Japan runs at the speed of 150-215 m/h
• Traffic Control
• Financial Institutes e.g. NYSE
• Entertainment industries (Cinemas, Production houses etc.)
• World e-commerce leaders, including Amazon, eBay, PayPal, and Walmart run their
platform on Linux
• Other fortune 500 companies e.g. Google, IBM, McDonalds, Facebook etc.
DOWNLOAD, INS TALL
AND C ONFIGURE
LINUX
Lab
Option 1 Design
Option 2
Virtual Machine Virtual Machine
VMWare player Oracle
VirtualBox
Virtualization software Cloud Services
What is Oracle VirtualBox?
• VirtualBox is a free and open-source hypervisor for x86
computers currently being developed by Oracle Corporation
• It installs on your existing Intel or AMD-based computers, whether
they are running Windows, Mac, Linux or Solaris operating
systems. It extends the capabilities of your existing computer so
that it can run multiple operating systems on one hardware at the
same time
Linux Windows MAC
Oracle Virtual Box
Operating System (Windows or MAC)
Hardware
ORACLE
V IRTUAL BOX
DOWNLOAD AND
INSTALLATION
V MWARE WORKS TATION
PLAYER
Download, Installation and
Configuration
CentOS vs. CentOS
Stream
• Brief history of CentOS
Community Enterprise Operating System
2004
Greg Kurtzer
Red Hat OS
2014
CentOS vs. CentOS
Stream
Before Feb 2021
Fedora RHEL
CentOS
After Feb
2021
Fedora CentOS Stream RHEL
CentOS vs. CentOS
Stream
Question???
Is it worth learning CentOS
*** ABSOLUTELY ***
Create Virtual
Machine
Virtual Machine
VMWare player Oracle
VirtualBox
Virtualization software
Download and Install
Linux (CentOS 7)
• You can use Ubuntu/Kali or any Linux OS
(CentOS = Recommended) 7
• 80% of the Corporate world uses RHEL Virtual Machine
• Regarding CentOS version
• CentOS 7
• CentOS 8 Stream
VMWare player Oracle
• CentOS 9 Stream VirtualBox
Virtualization software
Download and Install
Linux (CentOS 8)
Skip… 8
Go back Virtual Machine
• Create a VM VMWare player Oracle
• Download CentOS 8 Stream ISO VirtualBox
Virtualization software
• Install CentOS 8 Stream
Download and Install Linux (CentOS
9 Stream)
Go back… 9
Virtual Machine
• Create a VM
• Download CentOS 9 Stream ISO
• Install CentOS 9 Stream
VMWare player Oracle
VirtualBox
Virtualization software
Install Linux on
Option 2 Cloud
Skip…
Virtual Machine
Cloud Services
DIFFERENT WAYS
TO INSTALL OS
NEXT
LESSON
REDHAT LINUX
INS TALLATION
OPTIONAL
REDHAT LINUX
INSTALLATION
LINUX UbUNTU
INS TALLATION
OPTIONA
L
ORACLE V IRTUAL
MACHINE MANAGEMENT
Keyboard Keys Used in
Linux
Right Ctrl key
SYSTEM ACCESS
AND FILE
SYSTEM
Important Things to Remember in
Linux
• Linux has super-user account called root
• root is the most powerful account that can create, modify,
delete accounts and make changes to system configuration
files
• Linux is case-sensitive system
• ABC is NOT same as abc
• Avoid using spaces when creating files and directories
• Linux kernel is not an operating system. It is a small software within
Linux operating system that takes commands from users and pass them
to system hardware or peripherals
• Linux is mostly CLI not
GUI
• Linux is very flexible as compared to other operating systems.
Access to Linux System
There are 2 types of access
1. Console
2. Remote
The console is a direct access to an operating system when
it is connected through VGA, HDMI, DVI etc.
Access to Linux System
The 2nd type of access is remote where you connect to your operating
system remotely over the network
Putty
Clien
RDP Sharin t
g
Linux to Linux
SSH
Access to Linux System
Important:
Windows 10 or newer
version
SSH built-in client
ssh 192.168.1.5
Download and Install
Putty
If you are using Windows 10 or newer version
then you do NOT have to download or install
Putty
Download and Install
Putty
Putty is a software which allows you to connect from a Windows
system to Linux system remotely
192.168.1.5
Access to Linux from
MAC
• Open a terminal on your MAC
• Run the following command
• # ssh –l ayoub 192.168.1.5
Access Linux via Putty or
SSH
192.168.1.5
Linux
Linux
ssh 192.168.1.5
ssh –l ayoub 192.168.1.5
Access to Linux via
Putty
• The newer version of CentOS might not have the ifconfig command, therefore,
use
“ip addr” command instead
• To use ifconfig in 7.5 or later version then run = “yum install net-tools”
Access to Linux via
SSH
Linux
Command Prompts and Getting Prompts Back
• What are command prompts?
• A command prompt, also referred to simply as a prompt, is a short text at
the start of the command line followed by prompt symbol on a
command line interface
username hostname Prompt symbol
• To get your prompt back
• Ctrl + c
Introduction to Filesystem
• What is a Filesystem?
• It is a system used by an operating system to manage files. The
system controls how data is saved or retrieved
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Introduction to Filesystem
• What is a Filesystem?
• It is a system used by an operating system to manage files. The
system controls how data is saved or retrieved
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Introduction to Filesystem
• Operating system stores files and directories in an organized and
structured way
• System configuration file = Folder A
• User files = Folder B
• Log files = Folder C
• Commands or scripts = Folder D and so on
• There are many different types of filesystems. In general,
improvements have been made to filesystems with new releases of
operating systems and each new filesystem has been given a different
name
• e.g. ext3, ext4, xfs, NTFS, FAT etc.
FILE SYSTEM
STRUCTURE
File System Structure and its
Description
/boot Contains file that is used by the boot loader
/root (grub.cfg) root user home directory. It is not same
/dev as /
/etc System devices (e.g. disk, cdrom, speakers, flashdrive, keyboard
/bin 🡪 /usr/bin etc.) Configuration files
/sbin 🡪 /usr/sbin Everyday user commands
/opt System/filesystem
/proc commands
/lib 🡪 usr/lib Optional add-on applications (Not part of OS apps)
Running processes (Only exist in Memory)
/tmp C programming library files needed by commands and apps
/home
/var strace -e open pwd
/run Directory for temporary
files Directory for user
/mnt System logs
/media System daemons that start very early (e.g. systemd and udev) to
store temporary runtime files like PID files
To mount external filesystem. (e.g.
Navigating File System
• When navigating a UNIX filesystem, there are a few important commands:
"cd”
"pwd”
"ls“
• "cd" stands for change directory. It is the primary command for moving you around the
filesystem.
• “pwd” stands for print working directory. It tells you where you current location is.
• “ls” stands for list. It lists all the directories/files within a current working directory
• Using of TAB key to auto-complete
Linux File or Directory
Properties
Each file or directory in Linux has detail information or
properties
Type # of Links Owner Group Size Month Day Time Name
drwxr-xr-x. 21 root root 4096 Feb 27 13:33 var
lrwxrwxrwx. 1 root root 7 Feb 27 13:15 bin
-rw-r—r-- 1 root root 0 Mar 2 11:15 testfile
The second column is the number of hard links to the file. For
a directory, the number of hard links is the number of
immediate subdirectories it has plus its parent directory and
itself
Linux File Types
What is
Root?
• There are 3 types of root on Linux system
1. Root account: root is an account or a username on Linux machine and it is
the most powerful account which has access to all commands and files
2. Root as /: the very first directory in Linux is also referred as root
directory
3. Root home directory: the root user account also has a directory located in
/root which is called root home directory
Changing
Password
• You should change your initial password as soon as you
login
Command = passwd userid
Old password: - enter your current password
New password: - enter your new password
Retype new password: - re-enter your new password
File System
Paths
• There are two paths to navigate to a filesystem
✔ Absolute Path
✔ Relative Path
• An absolute path always begins with a "/". This indicates that the path starts at the root directory.
An
example of an absolute path is
cd /var/log/httpd
• A relative path does not begin with a "/". It identifies a location relative to your current position.
An example of a relative path is:
cd /var
cd log
cd
Creating Files and
Directories
• Creating Files
✔ touch
✔ cp
✔ vi
• Creating
Directories
✔ mkdir
Copying
Directories
• Command to copy a directory
• cp
• To copy a directory on Linux, you have to execute the “cp” command with the “-
R”
option for recursive and specify the source and destination directories to be copied
• cp -R <source_folder> <destination_folder>
Find Files and Directories
• Two main commands are used to
find files/directories
• find
• locate
Difference Between find and locate
• locate uses a prebuilt database, which should be
regularly updated, while find iterates over a filesystem
to locate files. Thus, locate is much faster than find , but
can be inaccurate if the database (can be seen as a
cache) is not updated
• To update locate database run updatedb
WildCards
• A wildcard is a character that can be used as
a substitute for any of a class of characters
in a search
• * - represents zero or more characters
• ? - represents a single character
• [] - represents a range of characters
Soft and Hard Links
• inode = Pointer or number of a file on the hard disk
• Soft Link = Link will be removed if file is removed or renamed
• Hard Link = Deleting renaming or moving the original file will not affect
the hard link
• ln
• ln -s
