Docker Tutorial for Beginners

Docker is an open-source platform that automates the deployment, scaling, and management of applications within lightweight containers. These containers provide a consistent environment for software development, allowing developers to build, ship, and run applications seamlessly across different computing environments. If you’re new to Docker and looking to get started, this tutorial will guide you through the basics.

What is Docker?

At its core, Docker is designed to simplify the process of packaging applications and their dependencies into a single unit, called a container. Containers are lightweight and can run on any machine that has the Docker engine installed, regardless of the underlying infrastructure. This eliminates the "it works on my machine" problem that developers often face.

Installing Docker

Before diving into the practical aspects of Docker, you need to install it on your machine. Here’s how to get started:

For Windows:

Download Docker Desktop: Go to the Docker Hub website and download Docker Desktop.
Install: Run the installer and follow the prompts. Make sure to enable the WSL 2 feature if you’re on Windows 10 or later.
Start Docker: After installation, launch Docker Desktop. It may take a few moments to initialize.

For macOS:

Download Docker Desktop: Similar to Windows, download Docker Desktop from the Docker Hub.
Install: Open the downloaded file and drag Docker to your Applications folder.
Start Docker: Open Docker from your Applications folder. It may take some time to start up for the first time.

For Linux:

Update the package index:
```
sudo apt-get update
```

Install dependencies:

sudo apt-get install 
    apt-transport-https 
    ca-certificates 
    curl 
    gnupg-agent 
    software-properties-common

Add Docker’s official GPG key:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

Set up the stable repository:

sudo add-apt-repository 
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu 
   $(lsb_release -cs) 
   stable"

Install Docker Engine:

sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io

Once installed, you can check if Docker is running correctly by executing:

docker --version

Your First Docker Container

Now that you have Docker installed, let’s run your first container. Docker allows you to run images, which are the blueprints for containers. For this tutorial, we will use the popular hello-world image.

Run the following command in your terminal:

docker run hello-world

What happens here is Docker checks to see if you already have the hello-world image on your machine. If not, it pulls it from Docker Hub. Once it’s downloaded, Docker runs the container and you should see a message confirming that your installation appears to be working correctly!

Basic Docker Commands

Now that you have a grasp of running your first container, let’s look at a few basic Docker commands:

Listing Docker Images

To see what images you have downloaded, run:

docker images

This will display a list of all images stored locally.

Running a Container in Interactive Mode

You can start a container in interactive mode, which allows you to execute commands inside the container. For example, let’s run an Ubuntu container:

docker run -it ubuntu

Once inside, you can run Linux commands. To exit the container, type exit.

Stopping a Running Container

To stop a running container, you first need to find out its container ID or name. Use:

docker ps

This command shows all currently running containers. To stop a specific container, use:

docker stop <container_id>

Removing Containers and Images

You can remove containers using:

docker rm <container_id>

To remove an image:

docker rmi <image_name>

Building Your Own Docker Image

Creating your own Docker images is straightforward. You need a Dockerfile — a text file that contains instructions on how to build your image.

Here’s a simple example. Create a file named Dockerfile:

# Start with a base image
FROM ubuntu:latest

# Install dependencies
RUN apt-get update && apt-get install -y python3

# Specify the command to run when the container starts
CMD ["python3", "--version"]

To build your image, run:

docker build -t my-python-image .

Replace my-python-image with a name you prefer for your image. The . refers to the current directory where your Dockerfile is located.

Running Your Custom Image

After building your custom image, you can run it using:

docker run my-python-image

You should see the Python version printed in the terminal.

Docker Compose

For managing multi-container applications, Docker provides a tool called Docker Compose. It allows you to define services, networks, and volumes in a YAML file, making it easier to manage complex applications. Here’s a simple example of a docker-compose.yml file:

version: '3'

services:
  web:
    image: nginx:latest
    ports:
      - "80:80"

  db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: example

To start this application, run:

docker-compose up

This command initializes both the web server and the database defined in your YAML configuration.

Exploring Docker Hub

Docker Hub is a public repository allowing users to share container images. You can search for images using the Docker CLI or through the Docker Hub website. To pull an image like nginx, you would run:

docker pull nginx

Once pulled, you can start up an Nginx server with a simple command:

docker run -d -p 8080:80 nginx

This starts the Nginx server in detached mode and maps port 80 in the container to port 8080 on your host machine.

This tutorial has covered the basics of Docker, from installation to running containers, creating images, and using Docker Compose. As you continue to explore Docker, you’ll find it to be an invaluable tool in streamlining development and deployment processes.

docker tutorial for beginners