Docker

What is Docker?

Docker is an open-source platform that automates the deployment, scaling, and management of applications using containerization. Containers are lightweight, portable, and self-sufficient units that include everything needed to run a piece of software, including the code, runtime, libraries, and system tools.

History of Docker

2013: Docker was released as an open-source project by Solomon Hykes and his team at dotCloud.
2014: Docker 1.0 was released, marking its first production-ready version.
2015: Docker Inc. raised significant funding and gained widespread adoption.
2017: Docker introduced the Moby Project, an open-source framework to assemble specialized container systems.
2018: Docker announced Kubernetes support, integrating it with Docker Enterprise.
2020: Docker refocused on developers, spinning off its enterprise business to Mirantis.

Basic Concepts

Image: A read-only template with instructions for creating a Docker container. Images are built from a Dockerfile.
Container: A runnable instance of an image. Containers are isolated from each other and the host system.
Dockerfile: A text file with instructions to build a Docker image.
Docker Hub: A cloud-based repository where Docker users can share and manage images.

Getting Started with Docker

1. Install Docker

Follow the instructions on the Docker website to install Docker on your operating system.

2. Write a Dockerfile

Create a Dockerfile to define your container. Here is an example for a simple Python application:

# Use an official Python runtime as a parent image
FROM python:3.9-slim

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Define environment variable
ENV NAME World

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

3. Build the Docker Image

Navigate to the directory containing your Dockerfile and run the following command to build the image:

docker build -t my-python-app .

4. Run the Docker Container

Run the container using the image you just built:

docker run -p 4000:80 my-python-app

This command maps port 4000 on your host to port 80 in the container.

5. Verify the Application

Open a web browser and navigate to http://localhost:4000. You should see your application running.

Summary

Install Docker: Follow the official installation guide.
Write a Dockerfile: Define your container's environment.
Build the Image: Use docker build to create an image.
Run the Container: Use docker run to start a container from the image.

Docker simplifies the process of deploying applications by using containers, which are portable and consistent across different environments.

Last modified: 14 December 2024