What is LINUX

What is Linux:-

• Linux is a free and open-source Operating-system and this operating system was designed by Linus Torvalds in 1991.

• This is typically packaged as a Linux distribution, which includes the kernel and supporting system software and libraries.

• Linux terminal can be used to accomplish all administrative tasks such as package installation, to automate functions, file manipulation and user management.

• Linux is a very lightweight OS so it can be used in various IOT devices like servers, systems, cellphones, gateways etc., and it can run 24/7/365.

• Inspiration: It was inspired by another system called UNIX.

• Open-Source meaning:-

  • Definition: Being "open-source" means that the source code is freely available and can be modified by anyone.

  • Community Collaborations: Due to its open nature, thousands of developers from worldwide contribute to its improvements.

    • example: Think of open-source as a community garden where everyone can plant, water, and enjoy the fruits and vegetables. Anyone can suggest changes or improvements.

Benefits of Using Linux:-

Open Source Nature

Definition: Open Source means the source code of the software is freely available to the public. Anyone can see, modify, and distribute the software.

• example: Think of open-source as a community garden where everyone can plant, water, and enjoy the fruits and vegetables. Anyone can suggest changes or improvements.

1. Cost-Effective

   • Definition: Linux can be downloaded, used, and distributed for free.

   • example: Instead of buying a pricey Productive, you're getting a nutritious and delicious cereal for free.

2. Security

   • Definition: Linux is known for its strong security features. Viruses and malware are less.

   • example: Living in a house with advanced security systems where unwanted guests (viruses) find it hard to get in.

3. Customizability

   • Definition: Users can modify Linux to suit their needs, right from the look and feel to core system operations.

   • example: It’s like customizing a vehicle. You can change its colour, add accessories, or even modify its engine and Looks.

4. Stability and Reliability

   • Definition: Linux systems are known to run for years without a crash they can be run 24/7/365.

   • example: Imagine a car that rarely breaks down or needs a mechanic.

5. Community Support

   • Definition: A vast community of users and developers regularly contribute to its improvement and are always ready to assist new users.

   • example: Moving to a new town but having a huge welcoming committee and helpful neighbours to guide you whenever you need.

6. Efficient Use of System Resources

   • Definition: Linux can run on older hardware efficiently, giving it a new life.

   • example: It’s like a magic potion that lets your old toy run as if it's a brand new toy.

7. Variety of Distributions

   • Definition: Linux offers a wide range of "flavours" or versions, each designed for specific needs.

   • Flavours: Ubuntu, Fedora, Cent Os, Amazon Linux, Red Hat Linux, Kali Linux, etc.,

   • example: Ice cream comes in various flavours to suit everyone’s taste, from vanilla to seasonal flavours.

8. Compatibility

   • Definition: Linux supports various arrays of file systems and is compatible with most programming languages.

   • example: Imagine a universal power adapter that can fit outlets from any country.

9. No Forced Upgrades

   • Definition: Users have the choice to upgrade their system whenever they feel like it.

   • example: It's like having a phone where you decide when you want to update to a new model, without any sales.

Architecture of Linux:-

Hardware Layer

• Definition: This is the actual physical layer of computers the various components like the CPU, memory, RAM, ROM, GPU, MotherBoard and hard drives.

Kernel

• Definition: The kernel is the core part of the OS. It directly interacts with system hardware and manages resources.

• example: If the OS is a restaurant, the kernel is the head chef. It oversees all the kitchen activities, ensuring all orders are cooked and ready on time.

Shell

• Definition: The shell is an interface for users to communicate with the kernel.

• example: The shell is like the counter at a restaurant where you place your order. You tell it what you want, and it conveys your order to the kitchen (kernel).

File System

• Definition: It organizes and stores data in a structured manner on storage devices.

• example: Imagine a library. The way books are arranged on shelves, categorized by genre, author, etc., is similar to how the file system organizes data.

Basic Commands of Linux:-

File Operations

• ls Lists files and directories.

  • Example: Think of it as looking at the table of contents in a book.

options:-
ls
ls -la (it lists all files and hidden files & there file permissions & details)
ls -l  (it lists all files without hidden files & file permissions & details)
ls -a  (it shows only files )
ls -d */ (to list only directories.)

Output:-

• cd Changes the directory.

  • Example: Imagine moving from one room in your house to another.

syntex:- 
cd filename
options:-
cd - ( Go to the last working directory.)
cd .. (Change directory to the one step back dir.)
cd    (Change directory to the home directory.)

Output:-

• mkdir Creates a new directory.

  • Example: It's like building a new shelf in your cupboard.

syntex:- 
mkdir filename
options:-
mkdir .filename (Make a hidden directory (also . before a file to make it hidden)
mkdir a b c d 5 (Make multiple directories at the same time.)
mkdir /home/affu/New-Dir  ( make a new folder in a specific location)
mkdir -p A/B/C/D  (Make a nested directory.)

output:-

• rmdir Removes an empty directory.

  • Example: Taking out an empty drawer.

syntex:- 
rmdir filename
options:-
rm -f file-name (ignore nonexistent files and arguments, never prompt)
rm -r (remove directories and their contents recursively) 
rm -d (remove empty directories)

output:-

• cp: Copies files or directories.

  • Example: Making a photocopy of a document.

syntex:-
cp source-file  destination-file

output:-

• mv Moves or renames files and directories.

  • Example: Shifting a book from one shelf to another or renaming its title.

syntex:-
mv Source-file  Destination-file (to Move-file)
mv Source-file  Rename  (this will change name and file will be in the same Directory)

output:-

moving file

Rename-file

• rm: Deletes a file.

  Example: Shredding a paper document.

syntex:- 
rm filename
options:-
rm -f file-name (ignore nonexistent files and arguments, never prompt)
rm -r (remove directories and their contents recursively) 
rm -d (remove empty directories)

output:-

Displaying File Contents

• cat Displays the content of a file.

  • Example: Reading a page of a book.

syntex:-
cat File_name

output:-

System Operations

top Displays real-time system stats and processes.

• Example: A leaderboard showing top performers.

top

output:-

shutdown: Shutdown or restart the system.

• Example: Turning off or restarting a device.

shutdown (this will do after 60 sec)
shutdown now (this shutdown imediatily)
reboot  (this will restart system)

Current working directory

• pwd current working directory

• Example: to know what is our current directory

pwd  (Print the name of the current working directory.)

output:-

File Permissions

• chmod Changes file permissions.

  • Example: Setting who can read or edit a shared document.

syntex:-
chmod [options] [mode] [File_name] 
options:-
-R    (Apply the permission change recursively to all the files and directories within the specified directory.)
-v    (It will display a message for each file that is processed. while indicating the permission change that was made.)
-c    (It works same as `-v` but in this case it only displays messages for files whose permission is changed.)
-f    (It helps in avoiding display of error messages.)
-h    (Change the permissions of symbolic links instead of the files they point to.)

Mode:-

1. Symbolic mode

   | Operators | Definition | | --- | --- | | + | Add permissions | | - | Remove permissions | | = | Set the permissions to the specified values |

2. | Letters | Definition | | --- | --- | | r | Read permission | | w | Write permission | | x | Execute permission |

3. | Reference | Class | | --- | --- | | u | Owner | | g | Group | | o | Others | | a | All (owner, groups, others) |

Examples of Using the Symbolic Mode:

• Read, write and execute permissions to the file owner:

chmod u+rwx [file_name]

• Remove write permission for the group and others:

chmod go-w [file_name]

• Read and write for the Owner, and read-only for the group and others:

chmod u+rw,go+r [file_name]

Octal mode

It is also a method for specifying permissions. In this method, we specify permission using a three-digit number. Where.

• The first digit specifies the permission of the Owner.

• The second digit specifies the permission for the Group.

• The third digit specifies the permission for Others. The digits

NOTE: The digits are calculated by adding the values of the individual permissions.

Examples of Using the Octal mode:

Suppose we give read and write permission to the file Owner. Read, write and executable permission to the Group. Read-only permission to the Other. They our command would be.

  chmod 674 [file_name]

Here.

• 6 represents permission of the file Owner which is (rw).

• 7 represents permission of Group which is (rwx).

• 4 represents permission of Other which is (r).

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Happy Learning

Thanks For Reading! :)

Afroz Shaik ✨