The docker explained: A Brief Look at containerisation

• What are Containers?
• Where Does Docker Fit Into All This?
• Practitioners of Docker in Their Daily Work
• The Main Advantages of Using Docker
• Challenges and Restrictions
• Future developments in Containerization
• Conclusion

Just imagine that you have built an excellent application. When you send it to your friend, though, or try running it on a server, everything goes wrong. Maybe they are using a different operating system, version of the required library files and/or something else in their environment is amiss. This is a problem that programmers always have faced for years -- "It works on my machine."

This is where containerization with Docker, and it is a technology thatperhaps was first introducedby Linux Containers, enters in. With it comes a triggering of the times. It is like dismantling a stage, setting up lighting, marking the position of actors, closing everything off downstairs and then shouting "this is what we see!"

What are Containers?

Before I read further posts from people who say sorry for poor grammar and spacing, please note that I am not an English speaker. But the most basic point of this text is: A container is exactly like an actual shipping container.

Without containers, companies had to load barrels, crates, and sacks of all shapes and sizes onto a ship. Everything was inefficient and liable to break.

The answer to this problem was shipping containers, which provide a standard box. Whether it is filled with electronics, clothing or food, the box moves easily from truck to train and then from the ship side of things without ever being opened.

Containers are totally new to software. They pack your application (code, libraries, system tools, settings) by itself within a neat little box called a container. Nothing outside the container can touch anything inside that doesn't belong to it far more cleanly and safely than ever before.

Where Does Docker Fit Into All This?

Docker makes the popular choice on containers easier, took the state-of-the art tools and ran with them. In fact though container technology existed before Docker arrived, by providing a simple set of tools Docker established a standard method that would be quickly shared between all programmers.

Docker does its job with just a few major building blocks.

• Dockerfile – a recipe: a simple text file that carries out step by step instructions for building a Docker image. For example, "start with a base Linux operating system,install Python,copy my application files,and specify the command to run when the container starts."
• Docker Image – the result of following such a recipe: an image is a lightweight, stand-alone,executable package that includes everything needed to run a piece of software. It's a template or a snapshot.
• Docker Container – an instance: This is a running version of an image.You can start, stop, move and delete containers. It is the "live" version of your application, running in its isolated environment. You can run many containers from the same image, just as with a batch of dough you can bake many cookies.

Practitioners of Docker in Their Daily Work

Docker is not just a hobbyist tool; it is an integral part of modern software development and operations (DevOps). Major companies such as Netflix, PayPal, and Spotify rely on it to power their services.

Software Development: Developers use Docker to provide consistent development environments. This means that a new team member can get a complex application up and running on his or her laptop in minutes by executing a single Docker container, rather than spending days manually installing software and re-configuring settings.

Cloud Computing: Docker containers are the perfect match for cloud because they are light and easily portable. Deploying them on cloud platforms like Amazon Web Services (AWS), Google Cloud, and Microsoft Azure is no sweat at all. A company can adjust its applications up or down by simply adding or removing containers, and pays only for what resources are actually used.

Microservices Architecture: A microservices model is used by many modern applications. Working from a single piece of software, a diverse group of small, independent services has been built. Docker is a good choice for this. Every microservice can be put into its own container, so that teams can develop, deploy, and scale it independently of the other services.

The Main Advantages of Using Docker

Then, why is Docker so loved? It solves several major problems in the software delivery pipeline.

• Portability: The "it works on my machine" question is almost completely eliminated with containerized applications. A container will work the same whether it is on a developer's laptop, in a testing server, or in production on the cloud.
• Efficiency: Containers are a lot smaller than traditional virtual machines (VMs). A VM virtualizes the whole OS, while a container virtualizes just the application's layer, sharing the host machine's OS kernel. As a result, you can run far more containers on any one server than VMs, saving hardware costs.
• Scalability: Need to deal with more visitors? Just spawn more identical containers. This process can become automatic so that applications scale based on demand.
• Speed: Docker dramatically quickens the process of development and deployment. Because containers are small and have minimal overheads, they can be started almost at once. This allows you to run tests, build prototypes, and maintain a continuous integration/continuous deployment (CI/CD) pipeline.

In other words: Containers allow applications and their dependencies to be isolated from one another and from the system. This makes security better and prevents conflict between different applications running on the same server.

Challenges and Restrictions

In spite of all its advantages, Docker is not a panacea. There are some challenges and restrictions to be borne in mind.

• Learning Curve: Even though Docker simplifies many things, it brings new concepts and tools. Teams have to put time into learning how to build images, manage containers and operate them at scale.
• Security is an Issue: A host's vulnerability could be all that is needed to compromise an entire environment. In this situation it's important carefully choosing trusted and bare base images, while regularly inventorying for known exploits.
• Data Management: Due to the fact that they are designed to be ephemeral, it can be time-consuming process for you when it happens. Stateless applications excel under this freedom, but maintaining the data (eg database) requires detailed planning with Docker shell scripts or other solutions, such as Linux loadable kernel modules (lkms). A particularly complicated aspect of all this is what to do with logs files...
• Complexity at Scale: Managing a few containers isn’t such a big deal. But when the user needs to keep up with hundreds or thousands of containers on multiple servers, this simple CLI can get really complex! Which is where container orchestration tools enter the picture. Enter Kubernetes for yet another magnificent layer to master.

Future developments in Containerization

Containerization is a permanent technology. The number of organizations utilizing cloud native infrastructure has grown rapidly and only continues to rise. The future will probably be about even greater abstraction, making it even easier for developers to create code and not have deal with the underlying infrastructure at all. Behind the scenes, serverless computing technologies, where you only pay for what your code cost at actual running time, often use containers

Containerization forms the foundation for an agile, resilient future that speeds software delivering (to market) In our world becoming more interconnected, software needs to be put out reliably and efficiently in diverse environments.

Conclusion

Docker and Containerization have changed an idea of how we develop, distribute, and run software. By encapsulating applications in tight, portable units, Docker solves many long-standing problems of uniformity and efficiency Building becomes easier for developers; scaling up a service's technology is possible now instead of difficult. This is also the core ingredient behind today's modern cloud computing: all accomplished through the use of containers. Despite its challenges though sometimes at first sight, it has out-grown every tool to be an indispensable part of our modern tech stack.

The excitement generated by container technology will spur new applications in the years to come.