SRJahirTech

DevOps Roadmap — Part 7: Docker & Containers

Agar DevOps ka heart Git hai, toh Docker uski muscle power hai.

Docker ne ek sabse bada problem solve kiya: "It works on my machine".

What Is a Container?

Container ek lightweight environment hota hai jisme:

• Application
• Dependencies
• Configuration

sab ek sath pack hota hai.

Laptop, server, cloud — sab jagah same behavior.

Docker vs Virtual Machine

• VM = heavy, full OS
• Container = lightweight, shared kernel

Isliye containers fast, cheap aur scalable hote hain.

Install Docker (Linux)

sudo apt update
sudo apt install docker.io -y

sudo systemctl start docker
sudo systemctl enable docker

docker --version

Docker Images vs Containers

• Image = blueprint
• Container = running instance

Image se multiple containers ban sakte hain.

Your First Docker Container

docker run hello-world

Agar ye chala, Docker correctly installed hai.

Running a Real Container

docker run -d -p 8080:80 nginx

Browser me open karo:

http://localhost:8080

Congratulations 🎉 Aapka first containerized server live hai.

Basic Docker Commands

docker ps

docker ps -a

docker stop container_id

docker rm container_id

Dockerfile — Automation Begins

Dockerfile ek instruction file hoti hai jo image banati hai.

FROM ubuntu
RUN apt update && apt install -y nginx
CMD ["nginx", "-g", "daemon off;"]

Ye DevOps ka real kaam hai — manual nahi, automated setup.

Build Image

docker build -t my-nginx .

docker run -d -p 8081:80 my-nginx

Why Docker Is Mandatory for DevOps

• CI/CD pipelines Docker use karti hain
• Kubernetes containers manage karta hai
• Cloud native apps Docker-based hoti hain

Docker skip = DevOps incomplete.

Common Beginner Mistakes

• Running containers as root
• Huge images banana
• No Dockerfile versioning

What Comes Next?

Containers ke baad aata hai Automation pipelines.