Docker Tutorial for Beginners [2025 Guide]

The Knowledge Academy 

To install Docker on Ubuntu use the following steps: 

Step 1: Open your terminal on Ubuntu 

Step 2: You then need to uninstall older versions of Docker that you may have installed using the following command: 

$ sudo apt-get remove Docker Docker-engine Docker.io 

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Step 3: Check that your system is up to date using the following command: 

$ sudo apt-get update 

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Step 4: Install Docker using the following command: 

$ sudo apt install Docker.io 

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You’ll then get a prompt asking you to choose between y/n - choose y 

Step 5: After installation, you will install the dependency packages using: 

$ sudo snap install Docker 

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Step 6: To check the Docker version installed use the following command; 

$ Docker --version 

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The Docker version installed at the time of this blog is 

Docker version 20.10.12, build 20.10.12-0ubuntu2~20.04.1 

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Step 7: You will then pull an image from the Docker hub using the following command: 

$ sudo Docker run hello-world 

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Step 8: To check if the image has been pulled and is in your system use the following command: 

$ sudo Docker images 

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You will get the following output: 

REPOSITORY    TAG       IMAGE ID       CREATED        SIZE 
hello-world   latest    feb5d9fea6a5   8 months ago   13.3kB 

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Step 9: To see all containers pulled use: 

$ sudo Docker ps -a 

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Step 10: To check the containers in a running state use: 

$ sudo Docker ps 

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You will get the following output: 

CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES 

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You have now successfully installed Docker on Linux Ubuntu. 

How to Install Docker on Windows and MacOS?

Follow these simple steps to install Docker on Windows and MacOS:

Windows:

• Download: Go to the website and get the right installer for your Windows.
• Install: Double-click the downloaded .exe file, follow on-screen instructions, like accepting the agreement and choosing the install location.
• Check: Open Command Prompt, type docker version. If it worked, you'll see your Docker version.

macOS:

• Download: Just like Windows, visit the website and grab the macOS installer (.dmg file).
• Install: Open the downloaded .dmg, drag the Docker icon to Applications, and double-click it.
• Accept Terms: When it opens, agree to the Docker Subscription Service Agreement.
• Verify: In Terminal, type docker version to see your installed Docker version.

After Installation:

To make sure everything works:

• Open Command Prompt/Terminal.
• Type docker pull hello-world to download a test image from Docker Hub.
• Confirm the download with docker images—you should see "hello-world."

Now that Docker is set up, you're ready to explore containerized applications and enjoy the benefits of their portability and isolation!

How to Use Docker Using Basic Docker?

After you have installed Docker, you can start using its features with just a few simple commands! Let's take a look at some basic things you can do with Docker.

Running pre-built Images:

1. Find an image: Browse the Docker Hub for ready-made images like "nginx" (web server) or "mysql" (database).
2. Pull the image: Run docker pull <image_name>, replacing <image_name> with your chosen image (e.g., docker pull nginx).
3. Run the container: Use docker run -it <image_name> to start an interactive container (replace <image_name> again). Add -p <host_port>:<container_port> to map ports between your host and the container (e.g., -p 8080:80 maps container port 80 to host port 8080).

Exploring your Container:

• Inside the container (accessible with docker attach <container_id>), use the image's default commands (e.g., nginx -h for help).
• View running containers with docker ps. Stop a container with docker stop <container_id>.

Building your own Images:

1. Create a Dockerfile defining installation steps for your application.
2. Build the image with docker build -t <image_name> .(replace <image_name> with your desired name).
3. Run the built image like any pre-built one using docker run.

Remember, this is just a starting point. Docker offers a vast array of commands and features. To dive deeper, explore the official documentation and online tutorials to unlock the full potential of containerized applications!

Core Components Of Docker  

K21Academy 

Docker has a client-server architecture. It comprises four main components that work together to enable a full software supply chain.

The four main components of Docker are discussed below: 

1. Docker client and server  

This is a command-line solution in which you would use your Linux system's terminal to issue commands from the Docker client to the Docker daemon. A REST API is used for communication between the Docker client and the Docker host. Similar commands, such as a Docker Pull command, can be issued, which will send an instruction to the daemon and perform the operation by interacting with other components (image, container, registry). The Docker daemon is a server that communicates with the operating system and provides services. 

2. Docker image

A Docker image is a template that contains Docker container instructions. This template is written in YAML, which stands for Yet Another Markup Language. 

The Docker image is created within the YAML file and then hosted in the Docker registry as a file. The image is composed of several key layers, each of which is dependent on the layer beneath it. Image layers are created in read-only mode by executing each command in the Dockerfile. You begin with your base layer, which typically includes your base image and operating system, and then you add a layer of dependencies on top of that. These instructions are then placed in a read-only file that will become your Dockerfile. 

It contains four layers of instructions From, Pull, Run, and CMD: 

1. From	Creates a layer based on Ubuntu
2. Pull	Adds files from your Docker repository
3. Run	Builds your container
4. CMD	Specifies which command to run within the container

3. Docker registry

The Docker registry is where you would host and distribute various types of images. The repository is simply a collection of Docker images that are built using YAML instructions and can be easily stored and shared. Docker images can be given name tags to make them easier to find and share within the Docker registry. One way to get started managing a registry is to use the Docker hub registry, which is open to the public. You can also make your registry for internal use. 

The registry that you create internally can contain both public and private images. Push and Pull are the commands that would be used to connect the registry. Push a new container environment created from your local manager node to the Docker registry with the Push command, and pull new clients (Docker images) created from the Docker registry with the Pull command. 

4. Docker container

The Docker container is a bundled executable package of applications and their dependencies; it contains all of the instructions for the solution you want to run. Because of the built-in structural redundancy, it is extremely light. The container is also portable by nature. Another advantage is that it operates completely independently. Even if you run a container, it is guaranteed not to be impacted by any host OS security or unique configurations, unlike a virtual machine or a non-containerized environment.

Memory for a Docker environment can be shared across multiple containers, which is especially useful when you have a virtual machine with a set amount of memory for each environment. 

The container is built with Docker images, and the Run command is used to run those images. 

5. Advanced Docker Components

There are two advanced Docker components. They use YAML to configure the application's services and perform the creation and start-up process of all the containers with a single command. We will discuss the components below: 

• Docker Compose: Docker-compose runs multiple containers as a single service. It accomplishes this by running each container independently while allowing the containers to interact with one another. 
• Docker Swamp: Docker Swamp is a container service in Docker. It allows IT, administrators, and developers, to create and manage a swarm node cluster within the Docker platform. Each Docker swarm node is a Docker daemon, and all Docker daemons communicate using the Docker API. A swarm is made up of two types of nodes: manager nodes and worker nodes. A manager node is in charge of cluster management tasks. Worker nodes receive and carry out tasks assigned by the manager node. 

Advantages and Disadvantages of Using Docker  

Dockers have numerous advantages as well as limitations. The introduction of Kubernetes eliminated all the shortcomings and solved all the problems concerned with Docker. It helped in managing containerized workloads and streamlining workflows. Therefore, a combined Kubernetes and Docker certification will add a great help once you have completed the Docker tutorial for beginners.

Here are some of the pros and cons in detail: 

Advantages of Using Docker  

Some of the key benefits of Docker are: 

1. Portability: Once you've tested your containerized application, you can deploy it to any other Docker system and be confident that it will perform exactly as it did when you tested it. 
2. Performance: Although virtual machines are an alternative to containers, the fact that containers do not include an operating system (whereas virtual machines do) means that containers have much smaller footprints, are faster to create, and are a startup. 
3. Agility: Containers' portability and performance advantages can help you make your development process more agile and responsive. Using containers and technology like Enterprise Developer Build Tools for Windows to improve your continuous integration and continuous delivery processes makes it easier to deliver the right software at the right time. 
4. Isolation: A Docker container containing one of your applications also includes any supporting software that your application requires. Other Docker containers containing applications that require different versions of the same supporting software are not a problem because the Docker containers are completely independent of one another. This also means that as you progress through the stages of your development lifecycle, you can be certain that an image created during development will perform the same as it moves through testing and potentially to your users. 
5. Scalability: If your applications require it, you can quickly create new containers. When using multiple containers, you can use a variety of container management options. More information on these options can be found in the Docker documentation. 
6. Reduces costs: Another perk of using Docker is that it reduces cost and saves strenuous efforts. Unlike the traditional process of software lifecycle being processed at an individual level, Docker facilitates collaboration and reduces development costs.
7. Optimised storage: Because containers are typically a few megabytes in size and consume very little disk space, a large number of applications can be hosted on the same host. 
8. Security: Docker ensures that applications running in containers are completely segregated and isolated from one another in terms of security by giving us complete control over traffic flow and management. 

Disadvantages of Using Docker  

Some of the downsides of using Docker include:

1. Containers Run at Slow Speed: Containers consume fewer resources than virtual machines. However, containers still incur performance overhead as a result of overlay networking, interfacing between containers and the host system, and so on. If you want to achieve 100 percent bare-metal performance, you must use bare metal rather than containers. 
2. Fractured Container Ecosystem [Text Wrapping Break]Although the Docker platform is open source, some container products do not work with others. Usually, this is due to competition among the companies that support them. 
3. Persistent Data Storage is Complicated: All data inside a container is designed to be lost forever when the container is shut down unless you save it somewhere else first. There are ways to persistently save data in Docker, such as Docker Data Volumes, but this is arguably a challenge that has yet to be addressed seamlessly. 
4. Graphical Applications Don't Work Well: Docker was created to be a solution for deploying server applications that do not require a graphical user interface. While there are some innovative approaches (such as X11 video forwarding) that can be used to run a GUI app inside a container, these solutions are at best clumsy. 
5. Not All Applications Benefit from Containers: Containers will benefit only from applications that are designed to run as a set of discrete microservices. 

Important Docker Commands  

In our Docker tutorial for beginner’s guide, we are sharing some commands used in Docker. Some of the common Docker commands include the following: 

1. Docker create 

It allows us to create a new container. Its syntax is: 

Docker create [options] IMAGE [commands] [arguments] 

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2. Docker ps 

The Docker ps command allows us to view all the containers that are running on the Docker Host. It only displays the containers that are presently running on the Docker Host. 

The syntax is: 

$ Docker ps 

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3. Docker start

This command starts any stopped container. Its syntax is as below: 

$ Docker start [options] CONTAINER ID/NAME [CONTAINER ID/NAME…] 

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An example: 

$ Docker start 1042924 

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4. Docker stop 

This command stops any running container. The syntax is as below: 

$ Docker stop [options] CONTAINER ID/NAME [CONTAINER ID/NAME…] 

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An example: 

$ Docker stop 1042924 

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5. Docker restart 

This command restarts any running container.

Its syntax is as below: 

$ Docker restart [options] CONTAINER ID/NAME [CONTAINER ID/NAME…] 

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An example of using the command is: 

$ Docker restart 1042924

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6. Docker run 

This command first creates the container and then launches it. In a nutshell, this command combines the Docker creates and Docker start commands. 

The syntax of the command is: 

$ Docker run [options] IMAGE [commands] [arguments] 

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7. Docker rm 

It is used to delete a container. The syntax is as below: 

$ Docker rm [options] CONTAINER ID/NAME [CONTAINER ID/NAME...] 

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8. Docker images 

This command lists out all the Docker Images that are present on your Docker Host.

$ Docker images 

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9. Docker rmi 

The Docker rmi command allows us to remove images from the Docker Host. 

The syntax of the command is as below: 

$ Docker rmi [options] IMAGE NAME/ID [IMAGE NAME/ID...] 

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Note: Anything enclosed within the square brackets is optional.  

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Conclusion

Docker is a very powerful containerization engine. when it comes to efficiently building, running, managing, and distributing your applications. Docker's intuitive approach simplifies the entire application lifecycle, making it a valuable tool for developers of all experience levels. 

If you are considering adopting Docker, learning, and understanding its ecosystem will make it very easy for you to adopt it. I hope this article has added knowledge on Docker and how to use it from this Docker beginner’s guide.