📦 Day 21 – Docker Basics

Today I completed the foundation of Docker and successfully installed it on my local machine. Below is a full summary of everything I learned and practiced.

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🧠 What I Learned

🔹 What is Docker?

Docker is a containerization platform that packages applications and all their dependencies into containers, ensuring consistency across environments.

Docker is a platform that allows you to:

• Package your app and all its dependencies into a lightweight, portable unit called a container.

• Run it anywhere: local machine, cloud, server — without worrying about compatibility.

🔹 Containers vs Virtual Machines

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✅ 3. 🧠 Why Docker Matters in DevOps?

• Consistency between dev, test, and prod

• Faster delivery via automation and CI/CD

• Efficient resource usage

• Modular architecture (microservices)

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🛠️ Installation & Setup

✅ Installed Docker on Ubuntu

sudo apt update
sudo apt install docker.io -y

###✅ Start the Docker daemon

sudo systemctl start docker

Enable Docker to start on boot (recommended)

sudo systemctl enable docker

###✅ Verify that Docker is running

sudo systemctl status docker

✅ Checked Docker Version

docker --version
docker info

✅ Added my user to Docker group (to run docker without sudo)

sudo usermod -aG docker $USER
newgrp docker

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🐳 Ran First Docker Container

✅ Test Docker is working

docker run hello-world

🟢 Output:

Hello from Docker!
This confirms Docker is installed and working correctly.

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📅 Pulled and Ran Nginx Container

docker pull nginx
docker run -d -p 8080:80 nginx

✅ Verified Nginx Container is Running

docker ps

🟢 Accessed in browser: http://localhost:8080

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🧹 Stopped and Removed Container

docker stop <container_id>
docker rm <container_id>

For example:

docker stop dd42ea9f5669
docker rm dd42ea9f5669

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🧠 Bonus Learning

• Created DockerHub account: ritesh355

• Understood Docker image lifecycle

• Understood basic Docker architecture:

  • Docker CLI

  • Docker Engine / Daemon

  • Docker Images & Containers

  • DockerHub registry

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✅ 6. 🧰 Docker CLI Basics

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✅ Summary

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🗓️ Next Up – Day 22: Dockerfile & Custom Images

We'll learn how to:

• Write a Dockerfile

• Build custom images

• Understand image layers

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🔗 My Work

📂 GitHub Repo: DevOps Journal
✍️ Blog Post: Hashnode DevOps Blog
🔗 LinkedIn: Ritesh Singh