Docker Tutorial Updated 2020

Designing and deploying apps nowadays requires a lot more than just writing codes. Architectures, multiple languages, discontinuous interfaces between tools and frameworks create vast complexities in each lifecycle stage. People want software that helps them create containerized apps easily and efficiently and no software can be better than Docker. By the end of this article, you will have a clear understanding of what is Docker, what are its features, benefits, and much more.

What is Docker?

Docker is a tool that is designed to easily create, deploy, and run the applications with the help of containers. It simplifies and accelerates the workflow as well as gives the developers their freedom to innovate with the tools, deployment environment, and application stacks of their choice for every project. But the questions arise that what do containers do? The answer is simple. Containers allow the developers to package up a single application with all the parts that it needs, whether it be libraries or other dependencies. In short, containers combine and deploy the application as one package. Docker is responsible for a significant performance boost and it further reduces the size of the application.

Why Docker?

Docker is the most popular tool among the organizations and other similar products because it makes it possible to run far more apps on the same old server and making it easy to package and ship programs. But why companies embrace it so much? It’s because Docker keeps it simple. Firstly, it has a friendly, CLI based workflow that makes running, building, and sharing containerized application accessible to the developers having all kinds of skill levels. Secondly, it moves fast, allowing the users to install a single package and run the application in minutes. They can code and test locally along with continuous consistency between development and production. Thirdly and most importantly, it pushes to a cloud-based application registry and collaborates efficiently with the team members.

Why you should use Docker?

There are many similar products in the market similar to Docker such as Apache Mesos, Rancher, etc. then why should one go with Docker? Let us understand this with an example. Suppose a user is working on an analysis in R programming. The user after finishing sends the code to his friend. When the friend runs the same code with the same data sets, it gives a bit different results. This can be because of a different version of R, a different operating system, or any other thing. These things don’t happen with Docker as it solves such problems easily. It acts as a computer inside a computer. The upside to using Docker is when your friend uses the code that you gave; it will give the same results as you did.

In short, one should use Docker because:

It ensures that your analysis is reproducible.
It has a great shareability which means you can send Docker containers to anyone who knows how to work with them.
You can wrangle dependencies easily that start from the operating system up to details like Latex package version and R.
It is portable and it sends Docker containers to another machine very easily because of which the users can set up everything on their computer and run analyses.

Docker Features

Docker is now considered one of the fastest-growing technology in web development and DevOps. It provides the following major features to its customers:

Security Management: Allows saving secrets and choosing to provide service access to particular secrets. Also, it includes commands like inspect, creates, etc.
Easy and Faster Configuration: The users can deploy the code in less time and effort that helps them to configure the system faster and easier.
Services: It is a list of tasks that specifies the state of a container. Every task represents the instance of a container that needs to be run.
Increase productivity: It has always helped to execute applications as well as reduced resources easing the technical configuration and increasing productivity.
Routing Mesh: Routing mesh is responsible for routing incoming requests for ports on available nodes to an active container. It enables connection even if no task is running.
Application Isolation: This provides containers that are needed to run applications in an isolated environment.
Swarm: This is a special scheduling and clustering tool for Docker containers.

Docker Architecture

Client-server architecture is used by Docker. The Docker client talks with the Docker daemon and it is responsible for distributing, building, and running the Docker containers. Both of them are capable of running on the same system. They communicate with the help of REST API over a network interface. Let’s have a look at its components.

Docker Daemon: It listens for the Docker API requests and manages objects like volumes, containers, images, etc. Also, it communicates with other daemons for managing Docker services.
Docker Client: Docker client is the main way for Docker users to interact with Docker. It allows the Docker client to communicate with multiple daemons.
Docker Registries: A Docker registry is responsible for storing Docker images. Docker Hub can be used by anyone as it is a public registry. In this, users can even run their private registry.
Docker Objects: Users create and use images, networks, plugins, volumes, and other objects while using Docker. This section briefs about those objects:

Images – It is a read-only template that creates a Docker container and comes with instructions. You can create your image or can use created by others.
Containers – It is a runnable instance of the image. With the help of Docker API or CLI, users can delete, stop, start, move, or create containers.
Services – Services are the objects that allow the users to scale containers across several Docker daemons that work together with multiple managers and workers.

Docker Benefits

Both the developers and system administrators benefit vastly from Docker. Developers can focus on writing the code without worrying about the system and the operational staff gets the flexibility and reduces the number of systems that are needed because of lower overhead and small footprints. Besides that, it provides many more benefits to them such as:

Security: There are many components in a large application that are separated into different containers. It has its security benefits such as if one container is compromised, others won’t be affected by it.
Reproducibility: Docker containers are identically the same on any other system that has Docker as the same container specifications are stored in a Dockerfile. Moreover, it gives a well-documented and constant environment making it easier to keep track and identify issues.
Environment Management: It helps maintain a different version of everything. It provides separate containers for development, production, and testing and can be easily deployed anytime.
Isolation: The applications are divided into containers due to which conflicting dependencies can be avoided. Users can even have multiple projects on a single server without creating conflicts on their system.
Docker Hub: The Docker Hub has many well-maintained images available. So, it can quickly pull a premade image making the process simple and fast.
Continuous Integration: Docker works well with tools like Jenkins, Travis, etc. So, whenever the source code is updated, the tools save the latest version as a Docker image, tags it with a number, pushes to the Docker Hub, and then deploys it to production.

Docker New Offerings

Docker is the most popular and user-friendly solution to share, configure, and save server environments using containers. Due to this, installing an application has become as simple as running Docker run or pull. In its latest update, Docker has included some new offerings that developers couldn’t resist the temptation of. This time, the Docker team focused on developer experience. It included the following things:

Improved collaboration and control
New vulnerability scanning and support enhance Docker Pro
Docker dashboard now welcomes local images and hub
Docker open sources compose for Microsoft ACI and Amazon ECS
Released Github Action V2
More secure than ever and it ensures best practices

Advantages and Disadvantages of Docker

Docker is a new and emerging technology. However, like any other tool, it is still under development. It has some limitations proving that it is not right for every project. In this section, we will learn about Docker’s pros and cons so that you can decide whether it is a good addition to your company or not.

Advantages –

For container management, Docker produces an API in an image format and a chance to use remote registries for container sharing.
It decreases the application size and enables them to deploy fast as it has the containers that carry minimal runtime requirements for it.
Users can share their containers with others easily.
The Docker images are small that results in rapid delivery and reduction in time to deploy a new application.
Users can pursue a container’s succeeding versions, can inspect irregularities, and can go back to previous versions too.
All the dependencies of an application can be grouped in separate containers. These containers can be allotted to other machines that have Docker and can be easily performed without any adaptability issue.

Disadvantages –

In Docker, graphical applications do not work well.
Data storage is intricate as all the data inside a container vanishes if it closes down unless you’ve saved it somewhere else.
Some applications do not benefit from Docker at all.
Although Docker is an open-source platform still some container products don’t work with other products at all.
Lastly, containers in Docker don’t work at bare metal rates because of interfacing, host system, overlay networking, etc.