🐳 Docker for DevOps Engineers.

💡 What is Docker?

• Docker is like a magic suitcase 🧳 for your applications. It lets you pack everything your app needs—libraries, tools, code, and even the runtime—into a neat container that works seamlessly anywhere.

• Whether you're on your local machine, a server, or in the cloud, you can unpack this container, and it will work exactly as intended.

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What is Containerization? 🧳

Imagine you're packing for a trip. Instead of throwing your clothes, shoes, and toiletries all over the car, you organize them neatly into suitcases.

📦Containerization works the same way for applications:

• It packages everything an app needs—code, libraries, dependencies, and runtime—into a container.

• These containers are lightweight and portable, so your app runs reliably no matter where it's deployed.

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Essential Docker Commands 🐧

1️⃣ Run Your First Container 🐣

docker run hello-world

• Downloads the hello-world image if it’s not already on your system.

• Starts a container that prints a welcome message.

• Confirms Docker is installed and running properly.

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2️⃣ List Running Containers 📋

docker ps

• Shows all containers currently running.

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3️⃣ List All Containers (Running + Stopped) 🗂️

docker ps -a

• Displays all containers, whether they’re running or stopped.

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4️⃣ Inspect a Container or Image 🔎

docker inspect <container_name_or_id>

• Shows detailed information about a container or image, like configurations, network settings, and file mounts.

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5️⃣ Check Port Mappings 🌐

docker port <container_name_or_id>

• Lists which host ports are mapped to your container ports.

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6️⃣ Monitor Resource Usage 📊

docker stats

• Provides real-time stats like CPU, memory, and network usage for running containers.

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7️⃣ View Running Processes 🧑‍🍳

docker top <container_name_or_id>

• Lists the processes running inside the container.

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8️⃣ Save an Image to a File 💾

docker save -o <file_name.tar> <image_name>

• Saves a Docker image to a .tar file.

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9️⃣ Load an Image from a File 📂

docker load -i <file_name.tar>

• Loads a Docker image from a .tar archive.

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📝Dockerfile : The Recipe for Your Containers.

create a Docker image. 🛠️

# Use a base image
FROM python:3.8-slim

# Set the working directory
WORKDIR /app

# Copy application files into the container
COPY . .

# Install dependencies
RUN pip install -r requirements.txt

# Run the app
CMD ["python", "app.py"]

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How to Use a Dockerfile?

1. Build the Docker Image 🏗️

docker build -t my-python-app .

1️⃣ docker build : This command tells Docker to create an image.
2️⃣ -t my-python-app : The -t flag gives the image a tag (name) for easy reference. Here, the image is named my-python-app.
3️⃣ . : The dot specifies the current directory as the context, which contains the Dockerfile and app files.

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2. Run the Container 🚀

docker run -p 5000:5000 my-python-app

1️⃣ docker run: Starts a new container from a specified image.
2️⃣ -p 5000:5000: Maps port 5000 on your local machine to port 5000 inside the container.

• First 5000: Port on your machine (host).

• Second 5000: Port inside the container.

• This allows your app running inside the container to be accessed locally on port 5000.

3️⃣ my-python-app: The name of the image to run as a container.

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📜How Docker Workflow Works?

1. Write a Dockerfile (Recipe) 📝

2. Build a Docker Image (Pre-packaged app) 📦

3. Run a Docker Container (The app in action) 🚢

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Closing Thoughts 💡

Docker is a powerful tool that makes application deployment fast, reliable, and fun! Happy Dockering! 🐳

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