Docker Images
What is a Docker Image?
A Docker image is a lightweight, standalone, and executable package that contains everything needed to run an application. It includes:
✔ Source Code – The application files.
✔ Runtime – Execution environment like Python, Node.js, etc.
✔ Libraries & Dependencies – Required packages.
✔ Configuration Files – System settings, environment variables, etc.
How Docker Images Work
• Docker images act as blueprints for containers.
• When you run a container, it is created from an image.
• Images are read-only; containers are instances of these images.
Working with Docker Images
1️⃣ Pulling an Image from Docker Hub
Docker Hub hosts pre-built images. To download an image, use:
docker pull nginx
This pulls the nginx image from Docker Hub.
2️⃣ Listing Available Images
To view all downloaded images on your system:
docker images
You’ll see a list with the image name, tag, size, and ID.
3️⃣ Removing an Image
You’ll see a list with the image name, tag, size, and ID.
docker rmi <image_id>
Building Custom Docker Images
You can create your own Docker image using a Dockerfile.
1️. Create a Dockerfile
Create a file named Dockerfile and add the following:
Dockerfile
# Base image
FROM python:3.9
# Set working directory
WORKDIR /app
# Copy application files
COPY . /app
# Install dependencies
RUN pip install -r requirements.txt
# Run the application
CMD [“python”, “app.py”]
2️⃣ Build the Image
docker build -t my_python_app.
3️⃣ Run a Container from the Image
docker run -d -p 5000:5000 my_python_app
Now your custom application is running inside a container!
Tagging & Pushing Images to Docker Hub
1️⃣ Tag an Image
docker tag my_python_app username/my_python_app:v1
2️. Push an Image to Docker Hub
docker push username/my_python_app: v1
Now others can download your image using docker pull username/my_python_app:v1.
Conclusion
• Docker Images are the foundation of containers.
• You can use pre-built images from Docker Hub or create custom images using a Dockerfile.
• Images make applications portable, scalable, and easy to deploy.
