Docker Basics: What It Is and How To Use It

In 2013, Solomon Hykes launched Docker to make container management systems accessible across various operating systems. Since then, Docker has grown to become a must-know for developers worldwide. It simplified how software developers build, run, and deploy applications and services. That innovation makes it possible to create an application and run it everywhere, regardless of the operating system.

This article provides an overview of what Docker is and how beginners can start developing with Docker.

What is Docker?

Docker is a software platform that allows you to package applications and dependencies into a single unit, called a container. This technology makes it easy to deploy and run applications on local development environments, remote servers, or the cloud.

Developers use Docker to build apps in isolation from one another—such that it creates a set of namespaces for every container you run. That makes debugging, updating, and redeploying apps easier. It also reduces operational costs, allowing users to run several applications on a single web server.

Basic Docker terminologies

Here are some common Docker elements that help you better understand this platform.

• The Docker daemon is a long-running process that manages Docker images and containers.‍
• The Docker client is a command-line interface that allows you to interact with the Docker daemon.‍
• The Docker registry is a repository for Docker images.‍
• Docker Image is a layered filesystem that contains all the templates, files, and directories needed to run a container.‍
• Dockerfile is a text file that contains all the Docker commands, in order, needed to build an image.‍
• Environment variables are settings that help your program run in a specific way.

Basic Docker commands

• Docker compose helps you run multiple Docker containers on one system.
• Docker pull allows you to upload an image from a repository so you can use it to create a container.‍
• Docker stop is a command you can use to stop a running container.‍
• Docker ps is a command that lists the containers on a docker host.

How does Docker work?

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Caption: A schematic diagram showing the docker architecture workflows.

Docker creates isolated environments, called containers, for applications. That means each application is executable and independent of the others without affecting the rest of the system.

The Docker architecture comprises two components: the Docker Engine and the Docker Hub. Docker Engine is the software that runs on your computer, while Docker Hub runs on a cloud-based service like AWS or Microsoft Azure. That helps you share and manage your applications on virtual machines.

The advantages of using Docker

Docker offers many benefits to developers and testers. These advantages include:

• Rapid deployment. Docker containers are portable. With Docker, you can quickly deploy your applications without worrying about setting up a new environment—which can save you time and hassle, especially if you often deploy your applications on virtual machines. In addition, Docker containers are lightweight and put less strain on the CPU storage and memory.

• Security. Using Docker containers can help create a more secure environment for your applications. By isolating your applications in their containers, you can control which resources they have access to and limit the effectiveness of cyber attacks. Docker containers can also run in read-only mode to reduce the possibility of tampering.

• Simple configuration. Docker containers isolate an application’s dependencies from the rest of the system, making the application much easier to configure and deploy—which helps to avoid potential conflicts between different versions of dependencies that may exist on the same host system.

• Continuous Integration (CI) efficiency. Docker provides a unique opportunity for continuous integration by allowing different parts of the CI process to be isolated from each other. The isolation allows running multiple CI jobs in parallel on the same build server, which can greatly improve the efficiency of the overall process, reducing the runtime.

• Disaster recovery and testing. The containerization technology also provides a platform for developers and DevOps to test applications. It allows them to create identical copies of the production environment, which is helpful for troubleshooting and disaster recovery. If one environment goes down, you can spin up your application in another with minimal downtime.

• Scalability. Docker containers can be easily scaled up or down as needs change, making them excellent for organizations experiencing rapid growth or fluctuating demand. With Docker, you can quickly add more containers to handle increased traffic without having to provision and configure new servers—and if traffic dips, you can easily remove containers to save resources.

• Compatible with Kubernetes. Developers can simplify various complexities of scaling and deploying Docker containers across multiple web servers by running them on Kubernetes. Kubernetes is a container orchestration system for automating deployment, scaling, and improving an application's functionalities.

• Build and deploy microservices. Microservices are software architectures that allow you to build and deploy individual services independently. Each microservice can be developed, tested, and deployed independently of other services. That makes it easier to manage and scale your application.

How to install Docker

The Docker installation process differs for each operating system. Whether you use Linux, Windows, or MacBook, this section will guide you through installing Docker on your computer.

Steps to install Docker on Linux Ubuntu

1. Before installing Docker on Ubuntu, you will need access to an Ubuntu server. Once you have that ready, you will need to update your existing list of packages by typing this in the command line interface (CLI): sudo apt-get update
2. Next, you need to install a few prerequisite packages, called dependencies. These packages will help ensure that Docker installs successfully. To do that, run the following command: sudo apt-get install apt-transport-https ca-certificates curl software-properties-common
3. Add the GPG key for the official Docker repository to the system.

Finally, pull down and install Docker with the command: sudo apt-get install docker-ce. Wait for it to install completely and run the application to ensure it works.

Steps to Install Docker on Windows

Before you can use Docker on Windows, you'll need to install it. Here's a quick guide on how to do that.

1. Download the Docker Toolbox from here.
2. Install Docker Toolbox on your Windows machine.
3. Once installed, open the Docker Toolbox and click on the Quickstart Terminal.
4. That will bring up a command prompt and automatically download and install the latest version of Docker.
5. Once Docker is installed, you can type in "docker run hello-world" to test it out.

Steps to Install Docker on Mac

Installing Docker on Mac is a simple process. However, remember that you'll need admin privileges on your computer to install Docker. Here's how to go about it.

1. Download Docker Desktop for Mac.
2. Open the file you just downloaded. It will be named something like “Docker.dmg.”
3. Double-click on the file to open it.
4. Drag the Docker icon to the Applications folder.
5. Eject the Docker disk image.
6. Open the Applications folder and double-click on the Docker icon.

How to use Docker

Docker has quickly become one of the most popular software tools, thanks to its ease of use and flexibility. Creating a Docker project is simple and only requires a few minutes. Here's a step-by-step guide.

1. Install Docker. Before you can use Docker, you need to install it. Following the steps detailed above, you can install your Docker application seamlessly on your Windows, Mac, or Linux device.
2. Share a repository. A repository is where all the files for a particular project are stored. To use Docker, you must sign up for a Docker ID. Then, you can create a new repository by clicking the Create Repository button. To add a file to your repository, click the Add File button. Once you have added all the files you want, click the Commit button. Finally, push your changes to GitHub by clicking the Push button. If you already have a GitHub account, this process should be familiar to you. After completing these steps, your repository will be available online and accessible by anyone with the link.
3. Build an image. To build a container image, you will create a Dockerfile. This file will contain all the instructions necessary for building your new image. In the Dockerfile, you need to specify the base image and the app dependencies, copy the app files into the container, and expose the container port. Next, open a terminal and go to the directory with the Dockerfile. You can then build the container image by typing the following in the CLI: $ docker build  -t  first-project.

That command downloads several layers and builds a container image using the Dockerfile. Behind the scenes, the builder downloads from the node:12-alpine image. It then installed the application's dependencies.

The -t tag on the command line is a container ID and usually proceeds with the name you’d like to give the image. In this case, the image's name is getting-started. Naming the image allows you to refer to it when running a container.

4. Run an image. To run the image, apply the docker run command and include the name of the image you're aiming to run. That is, “first-project.”

docker run -dp 3000:3000 first-project

The d and p commands are necessary to help the container run in the background. It is also necessary to include the port mapping to access the application. The 3000:3000 mapping indicates the host machine’s and the container's ports.

Next, use your browser to visit this address to see the running container: http://localhost:3000. At this point, you should also have the app showing on your Docker dashboard. Test the application and ensure it works, then mark it as complete. That will store the items in the backend.

5. Share your docker container image on Docker Hub. You can share your new container image on Docker Hub. By sharing your image, you can make it available to others who can use it to create their containers. To share your image, you must create an account and log in. Once logged in, you can click the Create button and select Create Repository. Give your repository a name and description, and then select whether you want it to be public or private.

Further Docker Resources

Docker helps you streamline your development process and increase your team productivity. If you want to learn docker, you can start by reading the official documentation. That will give you a good overview of how docker works and how you can use it to benefit your development process.

To become a Docker developer, you must have a strong understanding of Linux and Bash. You will also need to be proficient in at least one programming language. While there are many language options, most Docker developers use Node.js, Python, or Go.

Another way is to study various beginner Docker tutorials and segue to more advanced topics. Here are some resources to help your learning:

Hire a Docker developer or work as one yourself

Docker is a popular containerization tool used by developers worldwide, resulting in a rising demand for experts. If you're looking for work as a freelance Docker expert, you can go to Upwork and search for Docker-related jobs.

You’ll want to create a solid profile that includes relevant skills, experience, and any relevant certifications. Then, search for Docker-related jobs on Upwork and apply to those that interest you.

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Business owners can find professionals with the experience they need by creating an Upwork account and using the search bar to find Docker experts.

Upwork is not affiliated with and does not sponsor or endorse any of the tools or services discussed in this section. These tools and services are provided only as potential options, and each reader and company should take the time needed to adequately analyze and determine the tools or services that would best fit their specific needs and situation.