How to Get Started with Docker?

How to Get Started with Docker?

In the world of modern software development and IT infrastructure management, Docker has emerged as a game-changing technology. 


Docker allows you to package applications and their dependencies into lightweight, portable containers, making it easier to build, deploy, and manage applications across different environments. 


Whether you're a developer, system administrator, or DevOps engineer, learning how to get started with Docker is essential to staying competitive in the ever-evolving tech landscape.


This comprehensive guide will walk you through the fundamental concepts and practical steps to begin your journey with Docker. 


By the end of this article, you'll have a solid understanding of Docker's core components and be well-equipped to create, run, and manage containers effectively.


Read: Top Skills to Have as a Go Developer


What is Docker?


Docker is an open-source platform designed to make it easier to create, deploy, and run applications inside containers. 


Containers are lightweight, standalone executable packages that contain everything needed to run an application, including the code, runtime, libraries, and system tools. 


Docker containers are based on the concept of isolation, which means they run independently of the host system and other containers, ensuring consistency and predictability across various environments.


Key Docker Concepts


Before diving into the practical aspects, it's crucial to grasp some fundamental Docker concepts:





Installing Docker


The first step to getting started with Docker is installing it on your development machine which can vary according to the operating system being used.


Read: Advantages of Using Docker for Microservices


Docker Desktop (Windows and macOS)


If you're using Windows or macOS, Docker Desktop provides an easy-to-install package that includes Docker Engine, Docker CLI, and Docker Compose. Here's how to get Docker Desktop:



Docker Engine (Linux)


On Linux, Docker Engine can be installed directly from your distribution's package manager. The following are commands to install Docker on some popular Linux distributions:


 

 sudo apt-get update

 sudo apt-get install docker.io

 

 

 sudo yum install docker


  

 sudo dnf install docker


After installation, start the Docker service and enable it to run on system boot:


sudo systemctl start docker

sudo systemctl enable docker


You might also have to add a user to run Docker commands without sudo in the ‘docker’ group.


sudo usermod -aG docker your_username


For the changes to take effect, you will have to log out and log in again.


Running Your First Container


Once Docker is installed, you can verify that it's working correctly by running a simple container. Now all you need to do is open the terminal in your system and run the command as follows:


docker run hello-world


This command downloads the `hello-world` image from Docker Hub and runs it in a container. If everything is set up correctly, you'll see a message confirming that your installation appears to be working.


Building Custom Docker Images


While using existing images from Docker Hub is convenient, you'll often need to create custom images tailored to your applications. To do this, you'll use a `Dockerfile` to define the image's configuration and dependencies.


Dockerfile: A `Dockerfile` is a text file that contains instructions for building a Docker image. You specify the base image, add files and directories, configure environment variables, and define how the application should run. 


To help you understand a bit better, let’s look at the following example of Node.js app ‘Dockerfile’:


Dockerfile

# Base image should be an official Node.js runtime

FROM node:14


# Next, you need to set the container’s working directory

WORKDIR /app


# Copy package.json and package-lock.json

COPY package*.json./


# Install application dependencies

RUN npm install


# Copy the remaining source code of the application

COPY . .


# Run the command when the container starts

CMD [ "npm", "start" ]

```


Docker Build: To build a custom Docker image using the `Dockerfile` you've created, navigate to the directory containing the `Dockerfile` and run the following command:


perl

docker build -t my-node-app


This command builds an image named `my-node-app` from the current directory (`.`). You can replace `my-node-app` with a name of your choice.


Docker Compose: It refers to the tools used to define and run multi-container applications on Docker. It allows you to define the services, networks, and volumes in a single YAML file, making it easier to manage complex applications with multiple containers.


Here's a simple example of a `docker-compose.yml` file for a web application with a frontend and a backend service:


yaml

version: '3'

services:

 frontend:

  image: my-node-app

  ports:

   - "80:80"

 backend:

  image: my-database-image

  environment:

   MYSQL_ROOT_PASSWORD: mysecretpassword



To start the application defined in the `docker-compose.yml` file, run the following command in the same directory:


docker-compose up


Docker Compose will create and start the containers as defined in the YAML file.


Read: How to Build a Brand?


Managing Docker Containers


As you work with Docker, you'll frequently need to manage containers. Some of the most used commands for managing Docker containers are:


Starting and Stopping Containers: 


 docker start container_name_or_id



 docker stop container_name_or_id


Viewing Container Logs:

You can view the logs generated by a container to troubleshoot issues or monitor its output. Use the `docker logs` command:


docker logs container_name_or_id


Removing Containers:

You should use the `docker rm` command to remove a container as follows:


docker rm container_name_or_id


Keep in mind that removing a container also deletes all data associated with it, unless you've configured data volumes to persist data outside the container.


Conclusion


Docker has revolutionized the way we develop, deploy, and manage applications by simplifying the process of packaging and running software in containers. 


In this guide, we've covered the core concepts of Docker, installation steps for different platforms, creating custom Docker images, using Docker Compose, and managing containers effectively.


Read: Docker Launched Docker Enterprise 3.0


As you continue your journey with Docker, explore more advanced topics such as container orchestration with Kubernetes, continuous integration and deployment (CI/CD) pipelines, and best practices for optimizing your Docker workflows. 


By mastering Docker, you'll be better prepared to tackle the challenges of modern software development and infrastructure management. Happy containerizing!