What is Docker And How Does it Work

Software development is a process that evolves every year, but very few things in the industry have become the standard, like Docker.

Since 2013 when it was publicly released, Docker has been used for developing, shipping, and running applications. To this day, it’s a vital part of software development that many experienced developers use.

In this article, we’ll be covering what exactly Docker is, the advantages, and disadvantages of using it, and how it actually works.

What is Docker?

Docker is an open-source containerization platform that develops, ships, and runs apps separate from your local or host infrastructure. It’s a platform that creates and manages containers that are isolated from one another but can communicate with each other through defined channels.

The reason why Docker is a popular PaaS is because of the concept of containers, where they use fewer resources than VMs.

What Are Containers and What Do They Solve?

Before we elaborate on what Docker does, let’s first understand its components. 

All apps and programs are developed to run in specific environments. These environments either have the libraries or tools required by the app or run the software version that the app is compatible to run on. 

Containers are such environments and include all of the libraries and tools for apps to run in. What a container does is pack these apps inside containers together with the app’s libraries and tools so that it can run anywhere without having to rely on the host’s environment.

Here’s a simple analogy:

IKEA sells furniture that requires self-assembly. But, how do they know that all their customers have the tools to assemble their furniture? They don’t. IKEA ships the tools together with the furniture so any customer in the world can set it up the moment the IKEA package arrives on their doorstep.

This is essentially how containers work, making developing and shipping software easier. By including all the tools necessary in the container environment, developers no longer have to worry about incompatibility issues with different servers or hosts. Another term that’s often thrown around with containers is microservices.

What Does Docker Do?

Docker is simply a platform that manages these containers so that you can build different, specific environments easily.

The Docker platform lets developers and programmers use containers seamlessly throughout their workspace. Whether you’re an in-house or remote team with members around the world, using Docker to ship and run your containers is a low-cost way of building software more efficiently. 

But there are many more benefits to using Docker aside from convenience. We’ll talk more about how containerization is faster, more secure, and better suited for scaling, later on in this article.

What Does Docker Solve?

Docker solves the problem of creating containers yourself and managing them across an entire team. This becomes especially important when you want to optimize the workflow of your development process. 

The Advantages and Disadvantages of Using Docker

Aside from just the managerial side, Docker also solves numerous other complex, arduous problems. 

Here are the key advantages of using Docker

• Reliability. Containerization with Docker ensures that your apps will run virtually anywhere that has Docker installed. You don’t have to worry about having incompatible versions or manually installing dependencies. 
• Efficiency. A huge bottleneck in software development is when apps or software break down in computers without their environment. By using containers, you can get rid of these bottlenecks and streamline workflow to focus on developing software and not getting sidetracked by installing dependencies.
• Scalability. Having the option to quickly create new containers and deploy them allows for faster patches or updates to your software. Unlike monolithic programming which typically means building into existing code and then restarting it to update the program, containers let you build on top of each other independently. This means that you can add and remove containers without damaging other containers and their functionality, making it easier to scale your software.
• Accessible. The routine check-up and optimization process of software maintenance is also easier with containers. Since containers work independently from each other, you can configure, update, and then deploy a container without having to shut down or disturb other containers. This makes containers easily accessible.
• Lightweight. Containers are a lightweight alternative to virtual machines that need operating systems to function. Containers avoid the need to do this by sharing the host’s resources, like RAM and CPU, instead of virtual machines that require dedicated resources even if unused. 
• Version-freedom. Since containers are isolated from each other, you can run a container with the latest version of JavaScript while another container runs an older version. There’s no perfect version for every language and programmers are more familiar with some versions than others. Having the creative freedom to use any version without damaging other lines of code through containers makes your software all the more versatile.

Nothing is perfect and Docker is far from being the one-stop solution for everything. The platform does have its own fair share of disadvantages that you should look out for.

Disadvantages of using Docker

• Steep Learning Curve. Although Docker is convenient and fast, there’s no denying the learning curve it takes to become proficient with the platform. You won’t be a master at using Docker overnight and you can expect your team members to have the same struggle. You’ll also have to learn about Linux if you need to conduct maintenance or customizations on your Docker Engine.
• Platform to platform communication. Although containers talk to each other seamlessly, the companies that work in this space don’t always see eye to eye. Rival container companies don’t often work with each other, which can be a deal-breaker if you want to expand the tech you’re using.
• Temporary containers. Once a container’s use is finished, such as when it finishes a process and is no longer used, the container shuts down together with all the data it processed. The data isn’t saved unless you use Volumes to store your data to the Docker Engine. This isn’t necessarily a bad thing, but it’s something noteworthy for the development process of your software. Docker has no automated solution for this yet.
• Command line interface. Docker’s interface is similar to a command line, making it a bad choice for running apps that require a graphical interface. It’s mainly optimized for apps and programs that are run through commands on a terminal. 

Lastly, a common problem new companies face with Docker is when they try to use it without understanding how to design and orchestrate development architecture first. Docker isn’t meant to be a one-size-fits-all platform and some programs are just better off without it.

How Docker Works

Docker works on a client-server basis. The Docker client, which is what you see, talks to the Docker daemon which takes care of executing and managing tasks. 

Docker’s Core Components and Architecture

Beneath all that, there are more features from Docker that serve different functions. For today, we’ll only be focusing on Docker’s four core components.

Docker Client

The Docker client is the interface between you and the Docker daemon. This is where you’ll be inputting your commands, running programs, and mainly interacting with Docker. 

Docker Daemon

The daemon is what manages everything on your Docker platform, whether it’s images, containers, volumes, or networks. In simpler terms, this is the mastermind behind your entire Docker operation. All the commands you send through the client are processed by the daemon and managed by it. Daemons can also connect with daemons from other servers. 

Docker Registries

The Docker registry is an open-source system where you can store and download Docker images. You can even set up a private registry in your workspace that’s shared with your colleagues. 

Docker Images

Docker images are read-only files with instructions for creating Docker containers. In simpler terms, it’s like a blueprint that tells the Docker daemon what environment to run. This is part of what makes container creation much easier and faster. Combined with the Docker registry, you can find presets of images that are publicly available or even create custom ones for your workspace that your colleagues can use.

Docker or Kubernetes

A question that’s often asked by newcomers to Docker and containerization is “What’s better, Docker or Kubernetes?”

The answer to that is surprisingly simple: both. 

What is Kubernetes?

Kubernetes is a system developed by Google to manage deployment automation and containerized services. It’s built to handle and manage containers in the hundreds or thousands, and to optimize how these containers work with each other. Kubernetes does this through nodes that are built for special functions.

These nodes can be categorized into two things: workhorse nodes and head nodes. Workhorse nodes are responsible for anything computational and do all the heavy lifting. This requires more resources than the head nodes. On the other hand, head nodes are responsible for assigning tasks and receiving the final outputs. 

In short, Kubernetes is made to manage and optimize the entire workflow of containers with each other, and this makes it very different from Docker.

What’s the Difference Between Docker and Kubernetes?

Docker is a containerization platform that builds, ships, and runs containers. It’s a platform that lets you build containers just as easily as you can deploy them.

In contrast, Kubernetes shines more on container management and efficiency. It handles lots of containers and optimizes them to work faster through nodes.

After Action Report – Should You Use Docker?

So, should you use Docker for your software? Well, it depends.

Related: When And Why To Use Docker

Docker generally has the highest impact on your development process if you need to port your environment often. The next biggest consideration for using Docker is if you’re working with large teams that have to continually test your apps back and forth. Teams that work between developers and operations managers who need to run apps on different computers would find Docker a lifesaver.