IF Statement and IF ELSE Statement in Batch Scripting

When writing Batch Scripts, we often need to make decisions based on conditions. This is where the IF and IF ELSE statements are used.

They allow a script to perform different actions depending on whether a condition is true or false.

In this tutorial, we will learn how to use IF and IF ELSE statements with practical examples.

What is an IF Statement?

An IF statement executes a block of code only when a specific condition is true.

Syntax

if condition (
    command
)

Example 1: Basic IF Statement

  
@echo off

goto:main
:main

set /A number=5
if %number% equ 5 (echo This is IF statement)

goto:eof

  

Output

This is IF statement

Explanation

In this example:

• A variable named number is created.
• The value of number is set to 5.
• The IF statement checks whether the value equals 5.
• Since the condition is true, the message is displayed.

The keyword:

equ
means equal to.

Example 2: Checking a User Path

  
  @echo off

goto:main

:main

set /P path= Enter path
if %path% EQU C:\Users\user\Desktop\batch-scripting (
    cd %path%
    dir

)

goto:eof 

How It Works

User enters a path.
Batch compares the entered value with the specified path.

If both match:

• The script changes to that directory.
• The contents of the folder are displayed using dir.

Sample Input
C:\Users\user\Desktop\batch-scripting


Sample Output
Directory of C:\Users\user\Desktop\batch-scripting


This type of validation is commonly used in automation scripts.

What is an IF ELSE Statement?

The IF ELSE statement allows us to execute one block of code when a condition is true and another block when the condition is false.


Syntax

if condition (
    commands
) else (
    commands
)

Example: IF ELSE Statement

  
@echo off
goto:main
:main
set /P path= Enter path
if %path% EQU C:\Users\user\Desktop\batch-scripting (
    cd %path%
    dir
)
 else (
    echo Invalid path
)
goto:eof

  

Explanation

• Changes to the directory
• Displays folder contents
• If the path is incorrect
• D:\Projects

Common Comparison Operators

Example

if %number% GTR 10 (
    echo Number is greater than 10
)

Real-World Uses of IF Statements

System Engineers and IT Administrators commonly use IF statements for:

• Checking whether a file exists
• Validating folder paths
• Verifying user input
• Monitoring services
• Automating troubleshooting tasks
• Running backup scripts

Interview Questions

What is an IF statement in Batch Scripting?
An IF statement executes commands only when a specified condition is true.


What is the purpose of ELSE?
ELSE executes an alternative block of code when the IF condition is false.


What does EQU mean?
EQU stands for "Equal To".


Which command is used to take user input?
set /P


Why are IF statements important?
They allow scripts to make decisions and automate tasks based on conditions.

Conclusion

The IF and IF ELSE statements are fundamental concepts in Batch Scripting. They help automate decision-making and make scripts more interactive. Whether you are validating user input, checking files, or automating system administration tasks, conditional statements are an essential skill for every Batch Scripting learner.

 Understanding Local Scope and Global Scope in Batch Scripting

Variables are one of the most important components of Batch Scripting. As scripts become larger, managing variables properly becomes essential. This is where the concepts of Local Scope and Global Scope come into play.

In this article, we will understand how SETLOCAL and ENDLOCAL work and how they affect variable visibility inside a Batch Script.

Learn Local Scope and Global Scope in Batch Scripting with practical examples. Understand SETLOCAL, ENDLOCAL, variable visibility, and best practices for Windows automation and System Administration.

What is Variable Scope?

Variable scope determines where a variable can be accessed within a script.

In Batch Scripting there are two common scopes:

• Global Scope
• Local Scope

Understanding the difference helps prevent unexpected behavior when writing automation scripts.

Understanding SETLOCAL

Example Script

  
  
@echo off

goto :displayname

:displayname
setlocal
set /P name=Enter your name:
echo Hello, %name%!
endlocal

goto: eof
  

Understanding ENDLOCAL

@echo off

goto :displayname

:displayname
setlocal
set /P name=Enter your name:
echo Hello, %name%!
endlocal

set /P number=Enter a number:
echo You entered: %number%

goto: eof

• setlocal
• set name=Atul
• endlocal

Step-by-Step Execution of the Script

Step 1

Execution starts here:

• goto :displayname
• Control jumps to:
• :displayname

Step 2

A local environment is created:

• setlocal

Now all variables created afterward are local.




Step 3

User enters a name:

• set /P name=Enter your name:

Example:
Enter your name: Atul



Variable value:
name = Atul



Step 4

Display the value:
echo Hello, %name%!


Output:
Hello, Atul!



Step 5

Local environment ends:
endlocal

Now the variable:
name
no longer exists.


Step 6

User enters another value:
set /P number=Enter a number:

Example:
25

Since this variable is declared outside the local block, it remains available.

Output:
You entered: 25

What is Global Scope?

A global variable is accessible throughout the entire script.


Example:

  
@echo off

set company=HackingTruth

echo %company%

goto:eof
  

Output:

HackingTruth


The variable remains available until:

• Script ends
• Variable is modified
• Variable is deleted

Example of Local Scope

  @echo off
setlocal

set username=Atul
echo %username%

endlocal
echo %username%
  

Second output:

(blank)

Because username exists only inside the local environment.

Example of Global Scope

@echo off

set username=Atul

echo %username%

echo %username%

Output:

Atul
Atul

The variable is available everywhere in the script.

Why Use Local Scope?

Local variables are useful when:

• Creating reusable functions
• Preventing accidental variable modification
• Testing code
• Building large automation scripts

Benefits:

• Better script organization
• Reduced bugs
• Cleaner variable management

Real-World Example

Suppose a System Engineer writes a backup script.

Without local scope:

• set backup=C:\Backup
• Another function may accidentally overwrite:
• set backup=D:\Temp

Result:

• Backup process fails
• Wrong directory used

Using SETLOCAL prevents such conflicts.

Preserving a Variable After ENDLOCAL

Sometimes you want to keep a variable after ENDLOCAL.

Example:

  @echo off
setlocal
set username=Atul
endlocal & set username=%username%
echo %username%
  

Local Scope vs Global Scope

Real-World Uses for System Engineers

Local Scope is useful for:

• Software deployment scripts
• Backup automation
• User provisioning scripts
• Active Directory automation
• Network troubleshooting tools
• System inventory collection

Global Scope is useful for:

• Configuration values
• Common paths
• Server names
• Shared settings

Interview Questions

What is SETLOCAL in Batch Scripting?

• SETLOCAL creates a local environment where variables exist only within that block.

What is ENDLOCAL?

• ENDLOCAL ends the local environment and removes local variables.

What is the difference between Local Scope and Global Scope?

• Local variables are available only inside a SETLOCAL block, while global variables remain available throughout the script.

Why should System Engineers use SETLOCAL?

• It prevents variables from interfering with other parts of the script and improves maintainability.

What happens to variables after ENDLOCAL?

• They are removed unless specifically preserved.

Conclusion

Understanding Local Scope and Global Scope is essential for writing professional Batch Scripts. Using SETLOCAL and ENDLOCAL allows you to create safer and more maintainable automation scripts. As your scripts grow in complexity, proper scope management becomes increasingly important.

For aspiring System Engineers and future SecDevOps professionals, mastering variable scope is a foundational skill that helps build reliable Windows automation solutions.

Understanding Functions in Batch Scripting: CALL, GOTO, EXIT, and EXIT /B

As batch scripts become larger, writing all commands in a single block can make the script difficult to maintain. Functions help organize code into reusable sections, making scripts easier to read and manage.

In this article, we will learn how functions work in Batch Scripting using labels, the CALL command, GOTO, EXIT, and EXIT /B.

Learn Batch Scripting functions with practical examples. Understand CALL, GOTO, GOTO :EOF, EXIT, and EXIT /B to build reusable Windows automation scripts for System Administration and System Engineering.

What is a Function in Batch Scripting?

Unlike programming languages such as Python or Java, Batch scripting does not have traditional functions. Instead, functions are simulated using labels.

A label begins with a colon (:).


Example:

:function1

You can jump to a label using:

goto:function1

or call it using:

call:function1
  

Basic Function Example

  
  
@echo off 

:function1

echo This is function 1

:function2

echo This is function 2

call:function1
  

Explanation

In this script:

Two labels are created.
function1 prints a message.
function2 prints another message.
call:function1 invokes function1.



Output

This is function 1
This is function 2
This is function 1



Important Note

Without goto statements, Batch continues reading the script from top to bottom, executing labels as it encounters them. 

Using GOTO to Control Execution

The goto command transfers execution directly to a specific label.

Example:

  
  @echo off

goto:function3

:function1
    echo This is function 1

:function2
    echo This is function 2
    goto:eof

:function3
    echo This is function 3
    call:function1
  

How It Works

Step 1

Script starts at:

• goto:function3
• Execution jumps directly to:
• :function3

Step 2

Output:

• This is function 3

Step 3

• call:function1 executes:
• This is function 1

Output

This is function 3
This is function 1

Notice that function2 is skipped because execution never reaches it.

Understanding GOTO

One of the most useful statements in Batch scripting is:

• goto:eof

EOF means End Of File.

When a called function reaches:

• goto:eof

execution returns to the line immediately after the CALL statement.



Example:

• :function2
• echo This is function 2
• goto:eof

This behaves similarly to a return statement in other programming languages.

Function Example with EXIT



Example:

  
  
@echo off

goto:function3

:function1
    echo This is function 1

:function2
    echo This is function 2
    timeout 5
exit

:function3
    echo This is function 3
    call:function1

  

• exit

terminates the entire Command Prompt session.

If this script reaches the exit command:

• CMD window closes.
• Remaining commands do not execute.

Why Use EXIT?

Useful for:

Ending automation tasks
Stopping deployment scripts
Exiting maintenance operations

However, it should be used carefully because it closes the current command interpreter.

Understanding EXIT /B

A safer alternative is:

exit /B

Example:

  
  @echo off

goto:function3

:function1
    echo This is function 1

:function2
    echo This is function 2
    exit /B 0

:function3
    echo This is function 3
    call:function1


  

What Does EXIT /B Do?

Instead of terminating CMD:

• exit /B

only exits the current function or batch script context.

The command:

• exit /B 0

returns an exit code of 0.

Meaning of Exit Codes

 CALL vs GOTO

Many beginners confuse these commands.

• CALL
• call:function1
• Executes the function
• Returns to the next line after completion

Example:

• Start
• Function1
• Back to Start
• GOTO
• goto:function1
• Jumps permanently
• Does not return automatically

Example:

• Start
• Function1

Execution continues from the new location.

Real-World Uses for Functions

Functions are useful when:

• Displaying menus
• Automating backups
• Creating reusable code blocks
• Network troubleshooting scripts
• Software deployment scripts
• User management automation
• System information collection

Instead of writing the same commands repeatedly, create one function and call it whenever needed.



Practical Example: System Information Function

 

@echo off

call:sysinfo
goto:eof

:sysinfo
echo Hostname:
hostname

echo.
echo Current User:
whoami

echo.
echo IP Configuration:
ipconfig

goto:eof

Benefits:

• Cleaner code
• Easier maintenance
• Reusable logic

Interview Questions

What is a function in Batch Scripting?

A function is a labeled section of code that can be executed using the CALL command.



What is the difference between CALL and GOTO?

CALL returns to the original location after execution, while GOTO permanently jumps to another label.



What does GOTO do?

It exits the current function and returns control to the calling statement.



What is EXIT /B?

It exits the current batch context without closing the entire Command Prompt window.



Why are functions useful?

Functions improve code reusability, readability, and maintainability.

Conclusion

Functions are one of the most important concepts in Batch scripting. By understanding labels, CALL, GOTO, GOTO :EOF, EXIT, and EXIT /B, you can write structured and reusable scripts rather than long, repetitive command files.

For System Engineers and future SecDevOps professionals, mastering functions is essential because real-world automation scripts often depend on reusable code blocks and proper flow control.

Batch Scripting Basics for Beginners: Variables, Comments, User Input, and Arithmetic Operations

Batch scripting is one of the easiest ways to automate tasks in Windows. A batch file contains a series of commands that are executed by the Windows Command Prompt (CMD). System Administrators, IT Support Engineers, and System Engineers often use batch files for automation, troubleshooting, software deployment, and maintenance tasks.

In this article, we will explore some fundamental concepts of batch scripting, including displaying output, using comments, working with variables, accessing environment variables, and performing arithmetic operations.

Displaying Output with ECHO

The echo command is used to display messages on the screen.

echo off
echo "Hello World from a batch file!"
echo 1234
echo Hello Atul
  

• echo off hides the execution of commands.
• echo displays text on the console.
• It is commonly used to provide status messages to users.

Understanding @ Symbol

//echo off
@echo "This is for symbol.bat file"
@vol
@ver

• @echo displays text without showing the command itself.
• vol displays volume information of the current drive.
• ver displays the Windows version.

Working with Variables

@echo off
rem set filename=echo.bat
rem echo The name of the batch file is: %filename%
set filename=dir
echo The name of the batch file is: 
%filename%

• set creates a variable.
• %filename% retrieves the stored value.
• In this example, the variable contains the value dir.

Comments in Batch Files

@echo off
rem set
::cd %SystemRoot%
::dir

echo Below is the cmd path
echo %cmdcmdline%
::%ComSpec%
echo %ComSpec%

• %cmdcmdline%
• Displays the command line that started the current CMD session.
• %ComSpec%
• Displays the path of the Command Prompt executable.

Arithmetic Operations

@echo off

set /a sum = 10+10
echo The sum of 10 and 10 is: %sum%
Output
The sum of 10 and 10 is: 20
More Arithmetic Examples

Addition

set /a result=15+5
echo %result%

Subtraction

set /a result=20-5
echo %result%

Multiplication

set /a result=5*5
echo %result%

Division

set /a result=100/10
echo %result%

Modulus (Remainder)

set /a result=10%%3
echo %result%

Taking User Input

@echo off

rem echo Enter your name
rem set /P name=

rem echo Hello %name%, welcome to batch scripting!

echo Enter the first number:
set /P numb1=

echo Enter the second number:
set /P numb2=

set /A sum = %numb1%+%numb2%

echo %sum%

• set /p accepts input from the keyboard.
• Values entered by the user are stored in variables.
• set /a performs arithmetic calculations using those variables.

This technique is commonly used in interactive administration scripts.

 

Real-World Usage for System Engineers

Batch scripting is useful for:

• Automating repetitive tasks
• Running maintenance scripts
• Gathering system information
• Managing files and folders
• Creating startup and login scripts
• Troubleshooting Windows systems
• Automating software installation

Even though modern organizations prefer PowerShell for advanced automation, understanding Batch scripting remains valuable because many legacy systems still use .bat files.

Conclusion

Batch scripting provides a simple way to automate Windows tasks. By learning commands such as echo, set, rem, environment variables, arithmetic operations, and user input handling, you build a strong foundation for Windows administration and automation.

Multi-Container Applications in Docker: A Beginner's Guide

Modern applications rarely run inside a single container. In real-world production environments, different components of an application are separated into multiple containers. This approach improves scalability, maintainability, security, and performance.

In this guide, you'll learn what multi-container applications are, why they are important, and how Docker Networks and Docker Volumes help containers communicate and store data efficiently.

What Are Multi-Container Applications?

A multi-container application consists of multiple Docker containers working together to provide a complete service.

For example, a typical web application may have:

• React Frontend
• Node.js Backend API
• MongoDB Database

Instead of running everything inside one container, each service runs in its own container. 

React Frontend
      │
      ▼
Node.js Backend
      │
      ▼
MongoDB Database

This architecture follows the principle of separation of concerns, making applications easier to manage and scale.

 

Example Multi-Container Architecture

A typical Docker application may look like this:

Container 1: Frontend
Technology: React
Port: 3000

Container 2: Backend
Technology: Node.js
Port: 5000

Container 3: Database
Technology: MongoDB
Port: 27017

Frontend Container (React)
         │
         ▼
Backend Container (Node.js)
         │
         ▼
Database Container (MongoDB)

 
All containers communicate through a Docker Network.

Why Use Multiple Containers?

Using separate containers provides several advantages:

Better Scalability

You can scale only the service that needs additional resources.


Example:

• 1 MongoDB container
• 3 Backend containers
• 2 Frontend containers

Easier Maintenance

If the backend crashes, you can restart only the backend container without affecting the frontend or database.

Improved Security

Each service runs in an isolated environment.

Independent Updates

Frontend, backend, and database can be updated separately. 

Creating a MongoDB Container

Start a MongoDB container:

docker run -d --name mongodb mongo

Docker downloads the MongoDB image and runs it in the background.

Creating a Custom Docker Network

Starting the Backend Container

Run the backend container on the custom network:

• docker run -d --name backend --network mynetwork node

The backend can now communicate with other containers attached to the same network.


Starting the Frontend Container

Run the frontend container:

• docker run -d --name frontend --network mynetwork react-app

Now all services are connected through the Docker network.

Docker Volumes for Persistent Data
Containers are temporary by nature. If a database container is deleted, its data may be lost.
Docker Volumes solve this problem.

Create a Volume

• docker volume create mydata

List available volumes:

• docker volume ls
• Attach Volume to a Container
• docker run -v mydata:/app/data nginx

 
Benefits of Docker Volumes:

• Persistent storage
• Data survives container deletion
• Easy backup and migration
• Real-World Example: hackingtruth.org

Imagine hosting hackingtruth.org using Docker.

 

Application Stack:

• React Frontend
• Node.js Backend
• MongoDB Database

Production Architecture:

Frontend Container
        │
        ▼
Backend Container
        │
        ▼
MongoDB Container

Supporting Components:

Docker Network → Container communication
Docker Volume → Database storage
Multi-Container Architecture → Service separation


This setup closely resembles how modern applications are deployed in cloud environments.

Essential Commands

Create Volume
docker volume create mydata

List Volumes
docker volume ls

Create Network
docker network create mynetwork

List Networks
docker network ls

Run Container with Volume
docker run -v mydata:/app/data nginx

Run Container on a Network
docker run --network mynetwork nginx

Benefits of Multi-Container Applications

• Better scalability
• Easier troubleshooting
• Improved security
• Independent deployments
• Simplified maintenance
• Production-ready architecture

These advantages make multi-container applications the preferred approach in modern DevOps and cloud-native environments.

Conclusion

Multi-container applications are a fundamental concept in Docker and modern application deployment. By separating frontend, backend, and database services into individual containers, organizations achieve better scalability, reliability, and maintainability.

Combined with Docker Networks and Docker Volumes, multi-container architecture provides the foundation for deploying professional-grade applications in production environments. Learning these concepts is essential for anyone pursuing a career in DevOps, Cloud Engineering, System Administration, or Software Development.

Docker Compose, React & Node.js Deployment, and Container Troubleshooting Guide

As applications grow, managing multiple Docker containers manually becomes difficult. Imagine starting separate containers for React, Node.js, MongoDB, Redis, and Nginx every time you want to run your project.

Docker Compose solves this problem by allowing you to define and manage multi-container applications using a single configuration file.

In this guide, you'll learn Docker Compose, deploying React and Node.js applications, and common container troubleshooting techniques.

What is Docker Compose?

Docker Compose is a tool that allows you to define and run multiple Docker containers using a single YAML configuration file.

Instead of running multiple commands manually:

  
docker run ...
docker run ...
docker run ...

  

You can define everything inside a single file:

docker-compose.yml

and start all services with one command. 

Why Use Docker Compose?

Benefits include:

• Simplified container management
• Easy multi-container deployments
• Better configuration management
• Consistent development environments
• Faster application startup

Docker Compose is commonly used for:

• React Applications
• Node.js APIs
• MongoDB Databases
• Redis Caching
• Nginx Reverse Proxies

Understanding docker-compose.yml

A basic Docker Compose file looks like this:

In this example:

frontend runs the React application
backend runs the Node.js API
database runs MongoDB

All services are automatically connected through an internal Docker network.

version: '3'

services:
  frontend:
    image: react-app

  backend:
    image: node-app

  database:
    image: mongo

 In this example:

• frontend runs the React application
• backend runs the Node.js API
• database runs MongoDB

All services are automatically connected through an internal Docker network. Learn Docker Compose, deploy React and Node.js applications, and master container troubleshooting with practical examples. A beginner-friendly guide for DevOps and System Engineers.

Starting Docker Compose

Run:

• docker compose up

Docker will:

• Create networks
• Create containers
• Start services
• Connect containers

To run in the background:

• docker compose up -d
• Stopping Docker Compose

Stop all services:

• docker compose down

Docker removes containers and networks created by Compose.

 Deploying a React Application

  
FROM node:22

WORKDIR /app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 3000

CMD ["npm","start"]
  

Build the image:

• docker build -t react-app .

Run the container:

• docker run -d -p 3000:3000 react-app

Open:

• http://localhost:3000

Your React application should now be accessible.

Deploying a Node.js Application

Create a Dockerfile:

Build the image:

  
  FROM node:22

WORKDIR /app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 5000

CMD ["node","server.js"]
  

• docker build -t node-app .

Run the application:

• docker run -d -p 5000:5000 node-app

Access:

• http://localhost:5000

Deploying React, Node.js, and MongoDB Together

A production application often contains:



Docker Compose makes managing these services much easier.

Example:

React Frontend
       │
       ▼
Node.js Backend
       │
       ▼
MongoDB Database

 
Start everything:

docker compose up -d

Now all services run together.

version: '3'

services:
  frontend:
    image: react-app
    ports:
      - "3000:3000"

  backend:
    image: node-app
    ports:
      - "5000:5000"

  mongodb:
    image: mongo
    ports:
      - "27017:27017"

Container Troubleshooting

Troubleshooting is an essential Docker skill for System Engineers and DevOps Engineers.

Check Running Container

• docker ps

View all containers:

• docker ps -a 

Check Container Logs

Logs help identify startup issues.

docker logs container_name

Example:

• docker logs backend

Access Container Shell

Enter a running container:

• docker exec -it container_name bash

Example:

• docker exec -it backend bash

This is useful for checking:

• Application files
• Environment variables
• Network connectivity
• Installed packages

Inspect Container Details

View container configuration:

docker inspect container_name

This displays:

• IP Address
• Volumes
• Networks
• Environment Variables
• Mount Points
• Monitor Resource Usage

Check CPU and Memory:

• docker stats

Useful for identifying performance bottlenecks.

 Restart a Container

docker restart container_name

Example:

• docker restart backend

Common Docker Issues

Port Already in Use

Error:

• Bind for 0.0.0.0 failed

Solution:

• docker ps

Find the conflicting container and stop it.

Container Exits Immediately

Check logs:

• docker logs container_name

Usually caused by:

• Incorrect CMD
• Missing dependencies
• Application errors
• Cannot Access Application

Verify:

• docker ps

Check:

• Port mapping
• Firewall settings
• Container status 

Network Communication Issues

Inspect network:

• docker network ls
• Inspect container:
• docker inspect container_name
• Ensure containers are connected to the same Docker network.

Essential Commands

Start Compose:

• docker compose up -d
• Stop Compose:
• docker compose down
• View Containers:
• docker ps
• View Logs:
• docker logs container_name
• Enter Container:
• docker exec -it container_name bash
• Inspect Container:
• docker inspect container_name
• Monitor Resources:
• docker stats

Conclusion

Docker Compose simplifies the management of multi-container applications by allowing developers and system administrators to define services in a single configuration file.

Combined with React, Node.js, and MongoDB deployments, Docker Compose enables efficient application management and scalable infrastructure. Understanding container troubleshooting techniques further prepares you for real-world DevOps, Cloud Engineering, and System Administration roles.

Mastering Docker Compose and troubleshooting skills is a significant step toward becoming a proficient System Engineer or DevOps Engineer.

Docker Networking 

Docker networks allow containers to communicate with each other.

Example :

Frontend Container
        │
        ▼
Backend Container
        │
        ▼
Database Container
  

Without networking:

❌ Containers cannot easily communicate.

With networking:

✅ Containers communicate securely.



In docker networks there are 6 types of networks - 

1) bridge
2) host
3) overlay
4) ipvlan
5) macvlan
6) none


so steps by steps we will learn each and every docker networks.


1. Bridge - Its a default network as a bridge and if we will make container and don't make any other networks so its use by default network as a bridge from our host machine.

So let's see how to verify we have connected through bridge while making container.  if you are followed our docker's blog continuously then you know we have already images ,  container that we are already uploaded.

So, here we will run our docker desktop from our system (in windows search bar search docker desktop) are using our first command  

• docker run -it --name server1 ubuntu bash

Here:

• server1  = Container Name
• ubuntu   = Image Name
• bash     = Command to run

Here a ubuntu server is running even you can verify container name via 

• docker ps

Lets verify this docker container is connected via internet.

So as you can see the old one images and in that container we are facing some problems to apt-get or apt install iputils-ping -y because we are unable to use ping command.

So we will create new one file, docker images and install manually so follow the steps and do with scratch. 

Step 1: Create a folder

networking-dev/
├── Dockerfile

Step 2: Create Dockerfile

So go to your desire directory in your local machine and then create a folder

mkdir networking-dev

cd networking-dev  

and inside the folder open vs code editor  so type a file name without any extension.

code Dockerfile 

add this command and save it simple.

FROM ubuntu:24.04

RUN apt-get update && \
    apt-get install -y \
    iputils-ping \
    net-tools \
    iproute2 \
    dnsutils

CMD ["bash"]

This installs:

ping
ifconfig
ip
nslookup
other networking tools

Step 3: Build your image

Go inside the folder containing the Dockerfile: 

• docker build -t atul/networking-dev .

 
Notice the . at the end.

Docker will:

• Read the Dockerfile
• Download Ubuntu 24.04
• Install ping, net-tools, iproute2, dnsutils
• Create image atul/networking-dev

Verify:

docker images

You should see:

REPOSITORY           TAG
atul/networking-dev  latest

Run container

Now lets move into our real purpose of this blog docker networking via bridge

So, here we will run our docker desktop from our system (in windows search bar search docker desktop) are using our first command  

• docker run -it --name server1 atul/networking-dev

Previously we have server1 in container docker desktop so delete it. 

Inside container test:

ping google.com
ifconfig
ip addr
nslookup google.com

All should work.

• docker ps 

C:\Users\user\Desktop\app>docker ps
CONTAINER ID   IMAGE                 COMMAND   CREATED         STATUS         PORTS     NAMES
98acba8d0340   atul/networking-dev   "bash"    4 minutes ago   Up 4 minutes             server1

C:\Users\user\Desktop\app>

Verify which network a container is using

Run:

• docker inspect server1

Large output will appear.

To see only network information:

• docker inspect server1 --format='{{json .NetworkSettings.Networks}}'

Output:

{"bridge":{"IPAddress":"172.17.0.1"}}

This means:

Container: server1
Network: bridge
IP: 172.17.0.1

Practical Demo

Create two containers:

• docker run -dit --name server1  atul/networking-dev
• docker run -dit --name server2  atul/networking-dev

Check:

docker ps

After creating server in another terminal lets check IP address even try to ping each other

hostname -I 

ping 172.17.0.2 

We are able because both are connected with docker network by default bridge.

Enter server1:

docker exec -it server1 bash

Try:

ping server2

On the default bridge network, name resolution may not work as expected.

root@98acba8d0340:/# ping server2
ping: server2: Name or service not known
root@98acba8d0340:/#

we are not able to ping because of they are only default network as an IP address.

 A better practice is creating your own network: so for this open new terminal and run this command 

• docker network create mynetwork

open another terminal and type this command with server3 and --network mynetwork

hostname -I 

you can see the IP there is -  172.18.0.2 but this is in another class - 18 and previous one are in 17 class

Now we want to connect server 1 with my network mynetwork

and you can see in server1 having two different class IP

now we are able to run using name 

These are commands that we have used 

docker network ls
docker inspect server1
docker network create mynetwork
docker run --network mynetwork ...

Conclusion

Understanding Dockerfiles, custom image creation, and environment variables is essential for anyone learning Docker, DevOps, Cloud Computing, or System Administration.

By mastering these concepts, you'll be able to create reusable Docker images, automate deployments, and configure applications efficiently. These skills are widely used in real-world production environments and are frequently asked about in DevOps and System Engineer interviews.

Docker Volumes

What is a Docker Volume?

A Docker Volume is used to store data permanently, even if the container is deleted.


Without a volume:

Container Deleted
      ↓
Data Deleted
  

With a volume:

Container Deleted
      ↓
Data Remains Safe  

Why Do We Need Volumes?

Imagine a MySQL container:

• docker run mysql

All database data is inside the container.


If the container is removed:

• docker rm mysql-container

Your database is gone. 

Docker local file to docker container

How to use docker volume inside the docker ?


First we will create a file or file with code in local machine and then mount with docker and run nodejs code with nodemon and we will see live code's output in docker.

In our local machine --> go to desktop --> creating new folder --> then open in vs code --> then mount it

• cd Desktop
• mkdir app
• code app

Mount it 

• docker run -it node:latest

 Now we will mount from in our local machine's folder that we have created a folder name is app wtih node folder. so for this you can check our folder is there - docker container ls -a 

 use this command - docker run -it -v 

• -it -> interactive mode
• -v -> volume (with which you can attach any volume from your own machine to our docker container).
• copy of address of my folder 
• :   -> then mount with my container's address 

then you can see the above image and if we type uname there is linux and we will go docker container's directory cd home then ls for list directory.

 cd app

ls

there is a file called index.js  

index.js file is coming from our local machine. 

 you can check here cat index.js 

Now we will nodemon in our container and will run our node js file and if we try to change from our local machine then it will effect in our container where as we did run nodemon index.js file.

so first we will install nodemon as a globally.

npm install -g nodemon

then we will run nodemon index.js  

 if we change anything in our file index.js in our local machine then it will changes effect here because both are pointing same memory location and so if you are unable to changes anything as a output so run this command.

nodemon -L index.js 

Second way to create docker volume

This is the way to mount any file to docker container and now we will try to create a docker volume so for this  type this command and as well as open docker desktop that we have installed in previous blog article - check out Here - 

CLICK HERE

docker volume create data 

data -> is the name of volume 

Now you can check here if we type this command - docker volume ls

here it is showing  local as a our Driver local machine 

and

Volume name as a data that we have created just now 

Now we will attach our data volume to our docker container 

use this command - 

docker run -it -v data:/data node bash 

Here you can check here is a folder called as data so go to this data folder and again type ls command and nothing is there 

so we will create a file or folder atul.js for data volume and you can use this command mkdir atul.js and type again ls atul.js

so now we can say that what we have created a data volume that its attached with our local file. so for this you see this

open another terminal and type this command - 

docke run -it -v data:/myapp ubuntu 

go to this this directory

cd myapp

ls

and you can see that there is same atul.js is there   

lets say if we create a another file or folder in previous container terminal so we are able to see in another same file in our data volume because we have create a volume called as data and each and every container file pushed in volume data.

Conclusion

Understanding Dockerfiles, custom image creation, and environment variables is essential for anyone learning Docker, DevOps, Cloud Computing, or System Administration.

By mastering these concepts, you'll be able to create reusable Docker images, automate deployments, and configure applications efficiently. These skills are widely used in real-world production environments and are frequently asked about in DevOps and System Engineer interviews.