Tubagus Maulana Aghni

Introduction to Docker: What and Why?

What is Docker?

Docker is a containerization platform that allows you to package applications and their dependencies into lightweight, portable containers. Think of containers as standardized units that include everything needed to run an application: code, runtime, system tools, libraries, and settings.

Key Concepts

Virtual Machines vs Containers

Virtual Machines                    Containers
┌─────────────────────┐            ┌─────────────────────┐
│    Application      │            │    Application      │
├─────────────────────┤            ├─────────────────────┤
│    Guest OS         │            │    Dependencies     │
├─────────────────────┤            ├─────────────────────┤
│    Hypervisor       │            │  Container Runtime  │
├─────────────────────┤            ├─────────────────────┤
│    Host OS          │            │    Host OS          │
└─────────────────────┘            └─────────────────────┘

Why Use Docker?

1. Consistency Across Environments

“It works on my machine” problem solved
Same environment from development to production
Eliminates environment-specific bugs

2. Lightweight and Fast

Containers share the host OS kernel
Start in seconds, not minutes
Less resource overhead compared to VMs

3. Scalability

Easy horizontal scaling
Orchestration with Docker Swarm or Kubernetes
Microservices architecture support

4. Isolation

Applications run in isolated environments
Dependencies don’t conflict
Security through separation

5. Portability

Run anywhere Docker is installed
Cloud provider agnostic
Easy migration between environments

Docker Architecture

graph TB
    subgraph "Docker Host"
        subgraph "Docker Engine"
            A[Docker Daemon]
            B[REST API]
            C[Docker CLI]
        end
        
        subgraph "Containers"
            D[Container 1]
            E[Container 2]
            F[Container 3]
        end
        
        subgraph "Images"
            G[Image 1]
            H[Image 2]
            I[Image 3]
        end
    end
    
    J[Docker Client] --> B
    C --> A
    A --> D
    A --> E
    A --> F
    G --> D
    H --> E
    I --> F

Core Components

1. Docker Engine

The runtime that manages containers, images, networks, and volumes.

2. Docker Images

Read-only templates used to create containers. Like a blueprint or snapshot.

3. Docker Containers

Running instances of Docker images. Lightweight and executable.

4. Dockerfile

Text file with instructions to build Docker images.

5. Docker Registry

Storage and distribution system for Docker images (e.g., Docker Hub).

Real-World Use Cases

Development

Consistent development environments
Easy onboarding for new team members
Testing across different versions

Testing

Isolated test environments
Parallel testing
CI/CD pipeline integration

Production Deployment

Microservices architecture
Container orchestration
Cloud-native applications

DevOps

Infrastructure as Code
Continuous deployment
Environment parity

Docker Workflow

graph LR
    A[Write Code] --> B[Create Dockerfile]
    B --> C[Build Image]
    C --> D[Push to Registry]
    D --> E[Pull Image]
    E --> F[Run Container]
    F --> G[Deploy to Production]

Benefits Summary

Benefit	Description
Efficiency	Better resource utilization than VMs
Speed	Fast startup and deployment
Consistency	Same environment everywhere
Scalability	Easy to scale up or down
Security	Isolated application environments
Cost-effective	Reduced infrastructure costs

Getting Started

To begin your Docker journey:

Install Docker on your system
Learn basic commands (docker run, docker build, docker pull)
Create your first Dockerfile
Build and run your first container
Explore Docker Hub for existing images

Next Steps

After understanding what Docker is and why it’s useful, you should:

Docker revolutionizes how we develop, test, and deploy applications. It’s not just a tool—it’s a fundamental shift in how we think about application deployment and infrastructure management.