This repository contains beginner-friendly notes on Docker, Virtualization, Containers, and related DevOps concepts.

• What is Virtualization?
• Difference: VM vs Docker
• What is Docker Engine & dockerd
• Docker Images, Containers, Docker Hub
• How to install Docker in Ubuntu

1️Introduction to Virtualization
2️ Docker Basics
3️ Docker Installation
4️ Docker Components
5️ Examples

👇 It's Continue Below

My personal notes and cheat sheet on Docker and virtualization fundamentals... Read it asp....

Befor starting Docker we have to understand virtualization and its working for better understanding

Virtualization is the technology that allows creation of virtual machines and environments by dividing hardware resources through software.

• It allows one physical computer to behave like multiple computers.

A software called a Hypervisor divides the main system’s resources (CPU, RAM, Storage) so multiple operating systems can run at the same time.

• Creates Virtual Machines (VMs)
• Allocates system resources to each VM
• Keeps VMs isolated from each other
• Ensures VMs run smoothly and securely

1️Type 1 (Bare Metal)

• Installed directly on the hardware
• Faster and more powerful
• Used in big servers

2️Type 2 (Hosted)

• Installed on an existing OS
• Easier to use for personal computers

• Docker is a containerization platform.
• Instead of running a full OS like a VM, Docker runs applications in lightweight, isolated environments called containers.
• Example:
• Running a Node.js application in a container without installing Node.js on your main PC.

1️You download or create a Docker image

• Blueprint of app + all things needed

2️Docker uses that image to start a container

• Container is the running app

3️Each container is separated from other containers

• Safe & no conflicts

4️All containers share the host OS kernel

• That’s why Docker is fast and lightweight

5️You can start, stop, delete containers anytime easily

Docker Image

• An image is a read-only blueprint to create containers
• You can run many containers from one image

Docker Container

• A lightweight mini-environment to run applications
• Faster and smaller than a Virtual Machine
• Shares system resources with the host OS

Docker Engine

• Docker Engine is the complete Docker system that includes the Docker daemon (dockerd), Docker CLI, and Docker API.
• It provides everything required to build, run, and manage containers.

Docker Daemon

• Also called dockerd
• A background service inside Docker Engine
• It creates and manages containers, images, networks

Docker client

• It is user interface responsible for interacting with docker containers.

Docker Hub

• Docker Hub is an online store for Docker images.
• You can download ready-made images from there.
• You can also upload your own images to share with others.

If you are a developer or a system administrator, you undoubtedly come across a situation where you need to run multiple applications within same server or within multiple servers and chances are, you face conflicts while running applications. Suppose you need to run two different applications, one with a library JRE version 1.7 and other with JRE version 1.8, both in a same physical or virtual server. This will cause version conflicts on your server. Using docker containers developers can eliminate such situations and run many applications seamlessly and simultaneously.

Docker is available for different platforms. To install docker in ubuntu, you can follow the instructions as :

$ sudo apt-get update

• Always update before installing.

$ sudo apt install ca-certificates curl gnupg lsb-release

• This allows apt to use Docker’s repo securely.

$ sudo mkdir -p /etc/apt/keyrings curl -fsSL https://download.docker.com/linux/ubuntu/gpg
| sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

• This ensures packages you install come from Docker.

echo
"deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] \ https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) stable"
| sudo tee /etc/apt/sources.list.d/docker.list > /dev/

• Now Ubuntu knows where to fetch Docker from.

$ sudo apt update $ sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

This installs

• docker-ce (Engine)
• docker-ce-cli (command line)
• containerd.io (container runtime)

$ sudo docker run hello-world

• If Docker is installed correctly, this will pull and run a test container.