Docker Containers for Dummies: Simplifying the Complexities for Beginners
Tags: beginners, docker, devops, containers
Published: 2023-05-09 10:52:34

Docker containers are like a big deal in software development right now because they let you create and launch programs easily and move them around. But if you're just getting into it, it can seem pretty confusing. That's why I wrote this article - to give you the basics of Docker, explain its parts, and give you tips on how to use it. Whether you're a beginner or just curious, I'll help you understand what Docker is all about.

![Introduction to Docker containers](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ei1fnmmkvcr0owady903.gif)

<h1>Introduction to Docker containers</h1>

This post is for you if you are new to Docker containers. Docker has grown in prominence as a powerful platform for developers to use to design, deploy, and operate programs within containers in recent years. In this part, I'll explain what Docker containers are and why they're so popular.

<strong>What are Docker containers?</strong>

Docker containers, in a nutshell, are lightweight, standalone, and executable packages that include everything needed to run an application, including code, libraries, and system utilities. Because each container runs in its own isolated environment, it is simple to manage and deploy applications across multiple systems and platforms.

Docker containers are more efficient than traditional virtual machines since they share the host operating system kernel, which means they use fewer resources and can be deployed instantaneously. Docker offers developers with a consistent and dependable environment in which to build and test their apps.

<strong>Why should you use Docker?</strong>

Docker streamlines the development process by offering a standardized and portable environment in which to run applications. Developers can simply bundle their application code and dependencies using Docker, making it simple to deploy across many servers and environments without worrying about compatibility concerns.

Docker also enables rapid and efficient application testing and debugging by allowing developers to instantly spin up containers with multiple settings and test their code in diverse environments without the need for complicated hardware and software installations.

Finally, by isolating applications from the host system and other containers, Docker containers improve application security. This decreases the risk of security breaches and makes policies and controls easier to enforce.

![Getting started with Docker](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/249z8444mitvnwfhhzgb.gif)

<h1>Getting started with Docker</h1>

Now that we know what Docker containers are and why they are beneficial, let's look at how to get started with Docker. This part will go through installing Docker and utilizing the Docker command-line interface.

To get started with Docker, you need to install Docker Desktop on your machine. Docker Desktop is an application that provides a graphical user interface (GUI) and a command-line interface (CLI) for managing containers and images. Images are the templates that define how containers are created and configured.

Once you have installed Docker Desktop, you can use the GUI or the CLI to create and run containers. You can also use Docker Hub, a cloud-based service that hosts and distributes images, to find and download images for various applications. Alternatively, you can create your own images using a Dockerfile, a text file that contains instructions for building an image.

The Docker CLI has a straightforward syntax, with commands such as <em>'docker run'</em>,<em>'docker build'</em> and <em>'docker push'</em>. Developers can also use flags and parameters to tweak the commands' behavior.

Docker provides many benefits for developers and operators, such as:

- Faster development and deployment cycles

- Easier collaboration and sharing of applications

- Higher reliability and scalability of applications

- Lower resource consumption and costs

- Improved security and isolation of applications

To learn more about Docker, you can visit the official documentation at https://docs.docker.com/.

![Understanding Docker components](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/v7g8w9drpitcs08zrapd.gif)

<h1>Understanding Docker components</h1>

In this section, I'll go through the Docker components that make it such a strong development tool. Docker images, containers, and registries will be covered. Here are some of the main components of Docker:

- <strong>Docker Engine:</strong> This is the core of Docker that runs on the host machine and manages the containers. It consists of a daemon process (dockerd) that communicates with the Docker client (docker) and a REST API that provides an interface for external tools. The Docker Engine also includes a built-in orchestration tool called Swarm that can manage multiple nodes in a cluster.

- <strong>Docker Images:</strong> These are the building blocks of Docker applications. They are read-only templates that contain the application code, dependencies, libraries, and configuration files. You can create your own images using a Dockerfile or use pre-built images from Docker Hub or other registries.

- <strong>Docker Containers:</strong> These are the running instances of Docker images. They are isolated environments that have their own filesystem, network, and processes. You can start, stop, attach, and detach containers using the Docker commands. You can also inspect, monitor, and manage containers using the Docker API or tools like Portainer.

- <strong>Docker Volumes:</strong> These are persistent data storage units that can be attached to containers. They allow you to preserve and share data across containers and hosts. You can create and manage volumes using the Docker commands or the Docker API. You can also use plugins to connect volumes to external storage providers like AWS S3 or Azure Blob Storage.

- <strong>Docker Networks:</strong> These are logical networks that connect containers to each other and to the outside world. They provide network isolation, security, and service discovery for containers. You can create and manage networks using the Docker commands or the Docker API. You can also use plugins to integrate networks with external network providers like Calico or Weave.

- <strong>Docker Compose:</strong> This is a tool that simplifies the creation and deployment of multi-container applications. It allows you to define your application's services, dependencies, and configuration in a YAML file called docker-compose.yml. You can then use the docker-compose command to start, stop, and scale your application.

- <strong>Docker Registry:</strong> This is a service that stores and distributes Docker images. You can push and pull images from a registry using the Docker commands or the Docker API. You can use the public registry provided by Docker Hub or set up your own private registry using tools like Harbor or Nexus.

![Building Docker images](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0xa4vj8bkctf5svuhczo.gif)

<h1>Building Docker images</h1>

In this section, I'll go through the fundamentals of Dockerfile, the script used to produce Docker images, and how to create Docker images.

Create a Dockerfile in your project directory. A Dockerfile is a text file that contains instructions for building a Docker image.
Write the following content in your Dockerfile:

<pre>
	<code>
		# Use the official Node.js image as the base image
		FROM node:latest

		# Set the working directory inside the container
		WORKDIR /app

		# Copy the package.json and package-lock.json files from your host to your current location inside the container
		COPY package*.json ./

		# Install dependencies
		RUN npm install

		# Copy the rest of your app's source code from your host to your image filesystem
		COPY . .

		# Expose port 3000 to allow communication to/from server
		EXPOSE 3000

		# Define the command to run your app using CMD which defines your runtime
		CMD ["node", "app.js"]
	</code>
</pre>

Build your Docker image using the following command:

<pre>
	<code>
		$ docker build -t docker-app .
	</code>
</pre>

The <code>-t</code> flag lets you tag your image so it’s easier to find later using the docker images command.

Run your image as a container using the following command:

<pre>
	<code>
		$ docker run -p 3000:3000 -d docker-app
	</code>
</pre>

The <code>-p</code> flag maps port 3000 on your host machine to port 3000 on your container. The <code>-d</code> flag runs the container in detached mode, which means it runs in the background.

You can see your running container using the <code>docker ps</code> command.

You can stop your container using the <code>docker stop</code> command followed by the container ID or name.

You can tag and push your image to a Docker repository using the following commands:

<pre>
	<code>
		$ docker tag docker-app <your-dockerhub-username>/docker-app
		$ docker push <your-dockerhub-username>/docker-app
	</code>
</pre>

You need to have a Docker Hub account and be logged in using the <code>docker login</code> command before you can push your image.

![Running Docker containers](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/yte4np6jp1ly59hjr1dg.gif)

<h1>Running Docker containers</h1>

Docker containers offer a lightweight and effective method of packaging and deploying software. But how do you put them into action? All you need is the Docker command line interface (CLI) installed on your system.

<strong>Starting and stopping containers</strong>

Simply type <code>docker run</code> followed by the name of the image you want to run to start a container. To run a container based on the <code>nginx</code> image, for example:

<pre>
	<code>
docker run nginx
	</code>
</pre>

To stop a container, use the <code>docker stop</code> command followed by the container ID or name:

<pre>
	<code>
docker stop CONTAINER_ID_OR_NAME
	</code>
</pre>

<strong>Container logs and debugging</strong>

Sometimes you may need to inspect a running container or view its logs for troubleshooting purposes. You can do this using the <code>docker logs</code> command:

<pre>
	<code>
docker logs CONTAINER_ID_OR_NAME
	</code>
</pre>

If you need to run commands inside a running container, you can use the <code>docker exec</code> command:

<pre>
	<code>
docker exec -it CONTAINER_ID_OR_NAME bash
	</code>
</pre>
This will launch a Bash shell within the container, allowing you to perform commands as if you were logged in.

![Networking and storage in Docker](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/hs4waj7us6f0y9ka7kk8.gif)

<h1>Networking and storage in Docker</h1>

While running containers is simple, configuring their network and storage can be more difficult. Let's go through some fundamental topics in this area.

<strong>Working with networks in Docker</strong>

Docker automatically establishes a network for each container you run. However, there may be times when multiple containers are required to communicate with one another or to connect to the outside world. Docker networks come into play here.

To create a new network, use the <code>docker network create</code> command:

<pre>
	<code>
docker network create my-network
	</code>
</pre>

This will create a new network called <code>my-network</code>. You can now run containers and connect them to this network using the <code>--network</code> flag:

<pre>
	<code>
docker run --network my-network nginx
	</code>
</pre>

<strong>Docker data volumes</strong>

When you run a container, any data it generates or modifies is stored inside the container. But what if you want to persist this data even if the container is deleted or recreated? This is where Docker data volumes come in.

To create a new volume, use the <code>docker volume create</code> command:

<pre>
	<code>
docker volume create my-volume
	</code>
</pre>

You can then mount this volume inside a container using the <code>-v</code> flag:

<pre>
	<code>
docker run -v my-volume:/data nginx
	</code>
</pre>

This will mount the `my-volume` volume inside the container at the <code>/data</code> directory.

<h1>Best practices for Docker containers</h1>

Now that you understand the fundamentals, let's look at some best practices for operating Docker containers in production environments.

<strong>Container security</strong>

Security is an essential component of every production deployment. The following are some excellent practices to follow:

- Using non-root users to run containers

- Keeping container images and host operating systems up to date 

- Turning off superfluous services and programs within containers

<strong>Container performance optimization</strong>

Consider the following best practices to ensure your containers run as efficiently as possible:

- When feasible, use minimal foundation pictures

- Reduce the number of layers in your Dockerfiles 

- Use technologies like Docker Compose and Kubernetes to optimize resource allocation

<h1>Common use cases for Docker containers</h1>

Finally, let's look at some common Docker container use cases.

<strong>Web applications</strong>

Docker containers, which provide a uniform and portable runtime environment, are suitable for executing web applications. Docker can help you streamline your deployment process whether you're operating a simple static website or a big web app with several components.

<strong>Microservices architecture</strong>

Large programs are divided into smaller, more modular services in a microservices architecture. Docker containers, which provide a lightweight runtime environment for each individual service, are a logical fit for this strategy. This can assist to increase application scalability, maintainability, and overall performance.

<h1>Conclusion</h1>

Docker containers are legit awesome for making and launching apps. Once you get the hang of it, you'll be a pro. They have tons of perks like being portable, scalable, secure, and isolated. You can package everything into one unit and run it anywhere, even on your laptop or in the cloud. Plus, you can easily add or remove containers to scale your app and keep it secure by isolating it from other containers and the host system. This article has some sweet tips to help you get the most out of Docker and make dope apps crazy easily. You'll learn how to create, run, manage, and share Docker containers for different scenarios. Plus, you'll get some tips on the best practices and tools to use. Whether you're new to dev or a boss, you gotta have Docker containers in your toolkit. They'll make your life easier and your apps better. So, what are you waiting for? Start using Docker containers now! You won't regret it!

<h1>FAQ</h1>

<strong>What are the advantages of using Docker containers?</strong>

Docker containers have various benefits, including mobility, scalability, and consistency across settings. You can assure that your application and its dependencies function the same way on every computer by enclosing them in a container, independent of the underlying hardware or software configuration. This simplifies the development, testing, and deployment of programs while lowering the possibility of mistakes and conflicts.

<strong>Can I run Docker containers on my local machine?</strong>

Yes, you can run Docker containers on your local system if Docker is correctly installed and configured. Docker supports the majority of major operating systems, including Windows, macOS, and Linux, and offers a command-line interface for managing containers and interfacing with the Docker engine.

<strong>Where does Docker Desktop get installed on my machine?</strong>

By default, Docker Desktop is installed at the following location:

- On Mac: /Applications/Docker.app

- On Windows: C:\Program Files\Docker\Docker

- On Linux: /opt/docker-desktop

<strong>How do new users install Docker Desktop?</strong>

For new users, each Docker Desktop version includes a complete installer. The same is true if you skipped a version, which is uncommon because updates are performed automatically.

<strong>Can I run Docker Desktop on Virtualized hardware?</strong>

No, currently this is unsupported and against terms of use.

<strong>What are some common use cases for Docker containers?</strong>

Docker containers are used in a variety of contexts, including developing and deploying web apps, constructing microservices architectures, and performing large data workloads. Continuous integration and delivery, dev/test environments, containerized databases, and cloud-native apps are all prominent use cases for Docker containers.

<strong>Is Docker secure?</strong>

Docker containers are engineered to be safe by default, with features like container isolation, resource limitations, and network segmentation built in. Docker, like any program, can be vulnerable to security flaws if not correctly setup. To maintain the security of your Docker containers, recommended practices such as utilizing trustworthy images, reducing the attack surface, and deploying security patches on a regular basis should be followed.

Thank you for reading!
Soumyadeep Mandal @imsampro