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A brief introduction to Docker

Introduction

Docker is a platform that allows developers to create, deploy, and run applications in containers easily. Containers are lightweight, portable, and self-contained environments that can run on any machine with Docker installed. They provide a consistent and reproducible environment for applications to run in, which makes it easier to develop, test, and deploy software. With Docker, developers can package their applications and dependencies into a single container, which can then be deployed to any environment without worrying about compatibility issues.

Benefits

  1. Portability: Docker containers are portable, which means they can run on any machine with Docker installed, regardless of the underlying operating system or hardware.
  2. Consistency: Docker containers provide a consistent environment for applications to run in, which makes it easier to develop, test, and deploy software.
  3. Isolation: Docker containers provide a high degree of isolation between applications, which helps to prevent conflicts and ensures that applications run reliably.
  4. Efficiency: Docker containers are lightweight and use fewer resources than traditional virtual machines, which makes them more efficient and cost-effective.
  5. Scalability: Docker containers can be easily scaled up or down to meet changing demands, making them ideal for applications that handle varying levels of traffic or workload.

Difference between docker containers and Images

A Docker image is a container snapshot containing all the necessary dependencies and configuration files to run an application. It is a read-only template that can create one or more Docker containers. An image is created using a Dockerfile containing instructions for building the image.

On the other hand, a Docker container is a running instance of a Docker image. It is a lightweight, standalone, and executable package that includes everything needed to run an application, including the application code, runtime, system tools, libraries, and settings. Containers are created from images and can be started, stopped, and deleted.

In summary, an image is a static snapshot of an application and its dependencies, while a container is a running instance of that image. Images are used to create containers, and containers are used to run applications.

Let’s look at an example of how to dockerise a FastApi application.

Installation

Head over to the docker website and download docker for your OS.

Dockerfile

A Dockerfile is a script that contains instructions for building a Docker image. It is a text file that specifies the base image to use, the files and directories to copy into the image, the commands to run inside the image, and other configuration options.

When you run the docker build command, Docker reads the Dockerfile and executes each instruction to create a new Docker image. The resulting image is a container snapshot containing all the necessary dependencies and configuration files to run an application.

Dockerfiles are used to automate the process of building Docker images, which makes it easier to create consistent and reproducible environments for applications to run in. By defining the environment in code, you can ensure that the same environment is used across different machines and environments, which helps to prevent compatibility issues and makes it easier to deploy and manage applications.

Here’s an example Dockerfile for a FastAPI application:

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

# Set the working directory to /app
WORKDIR /app

# Copy the requirements file into the container at /app
COPY requirements.txt /app

# Install any needed packages specified in requirements.txt
RUN pip install --trusted-host pypi.python.org -r requirements.txt

# Copy the rest of the application code into the container at /app
COPY . /app

# Expose port 80 for the application
EXPOSE 80

# Define the command to run the application when the container starts
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "80"

Here’s how you can bring up the container from the command line:

Build the Docker image using the Dockerfile:

docker build -t my-fastapi-app .

Run the Docker container using the image:

docker run -p 80:80 my-fastapi-app

This will start the container and map port 80 on the host machine to port 80 in the container. You can then access the FastAPI application by navigating to http://localhost:80 in your web browser.

The last byte…

Docker is a platform that allows developers to create, deploy, and run applications in containers easily. Containers are lightweight, portable, and self-contained environments that can run on any machine with Docker installed. They provide a consistent and reproducible environment for applications to run in, which makes it easier to develop, test, and deploy software. With Docker, developers can package their applications and dependencies into a single container, which can then be deployed to any environment without worrying about compatibility issues.

Docker provides a rich ecosystem of tools and services to help you manage and deploy your applications, including Docker Hub, Docker Swarm, and Docker Compose. Docker Hub is a repository for Docker images where you can find and share images with other developers. Docker Swarm is a tool for managing a cluster of Docker hosts, which can be used to deploy and scale applications across multiple machines. Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to define a set of services, each of which can be run in its container, and specify how these services interact.

Overall, Docker is a powerful tool for managing and deploying applications, and it can help you simplify the development, testing, and deployment of complex applications.

Ali Kayani

https://www.linkedin.com/in/ali-kayani-silvercoder007/

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