🐳 What is Docker?

Docker is a platform for developing, shipping, and running applications in isolated environments called containers. It allows developers to package applications along with all their dependencies, ensuring they run consistently across different environments — from development to production.

🐳 Docker Architecture Overview

Docker provides a standard way to package and run applications using containers. Its architecture is client-server based and revolves around the use of images, containers, and a central daemon.

🖼️ Docker Architecture Diagram

⚙️ Docker Workflow

1. Developer writes a Dockerfile describing the app environment.
2. The image is built using

   docker build

   .
3. The image is stored in a registry (e.g., Docker Hub).
4. When deployed, the image is used to run containers.
5. Containers are networked and can use shared volumes for data persistence.

Docker’s architecture ensures consistency, isolation, and portability across environments — whether you're running locally or in production on Kubernetes, ECS, or any cloud platform.

🧱 Core Components

1. Docker Client

The command-line tool (

docker

2. Docker Daemon (dockerd)

The background service running on the host machine. It listens to API requests and manages Docker objects like images, containers, networks, and volumes.

3. Docker Images

Read-only templates used to create containers. Images are built using Dockerfiles and stored in registries.

4. Docker Containers

Running instances of Docker images. Containers are isolated, portable, and lightweight.

5. Docker Registries

Repositories like Docker Hub or private registries where Docker images are stored and shared.

6. Volumes and Networks

Volumes are used for persistent data, and networks manage communication between containers.

📦 Docker Image

A Docker image is a snapshot of a filesystem and parameters needed to run an application. Think of it as a blueprint that defines everything your containerized application needs: the operating system, app code, runtime, libraries, and environment settings.

🚀 Docker Container

A Docker container is a live, running instance of a Docker image. It is an isolated execution environment for your application. Containers are ephemeral and stateless by default but can persist data and state using Docker volumes.

💾 Docker Volumes

Docker volumes are used to persist data generated and used by Docker containers. They store data independently of the container lifecycle, ensuring your data isn’t lost when containers stop, restart, or are removed.

🌐 Docker Networks

Docker networks enable communication between Docker containers, the host, and external systems. You can define custom networks to organize and secure inter-container communication.

🛠️ Dockerfile

A Dockerfile is a script that automates the creation of Docker images. It contains step-by-step instructions like selecting a base image, installing dependencies, copying files, and setting a default command.

⚙️ Docker Compose

Docker Compose is a tool for defining and running multi-container applications using a YAML file. It simplifies configuring multiple services like databases, backends, and frontends.

🧬 Docker Compose File

A Docker Compose file is a YAML configuration that defines:

• Services (e.g., app, database)
• Volumes (for persistent data)
• Networks (for service communication)
• Build Instructions (for custom Dockerfiles)

Docker makes application delivery consistent and scalable. Understanding its components—images, containers, volumes, networks, Dockerfile, and Compose—helps you build modern applications with confidence.