Docker is a software platform for developing applications based on containers, which are small and lightweight execution environments that share the operating system kernel but execute in isolation. While containers have long been utilized in Linux and Unix systems, Docker, an open-source project established in 2013, made it easier than ever for developers to bundle their applications to “create once and run anywhere.”

Docker started out as a platform as a service (PaaS) before switching in 2013 to focus on democratizing the underlying software containers its platform was running on. It was founded in 2008 by Solomon Hykes in Paris as DotCloud.

Hykes originally demonstrated Docker at PyCon in March 2013, explaining that it was established in response to developer requests for the DotCloud platform’s underlying technologies. “We’ve always thought it’d be amazing to be able to say, ‘Yes, this is our low-level piece,'” says the group. Now you can work with us on Linux containers and do whatever you want with your platform.’ As a result, that’s what we’re doing.”

So Docker was created, quickly gaining acceptance among developers and catching the attention of high-profile technology companies such as Microsoft, IBM, and Red Hat, as well as venture capitalists prepared to invest millions of dollars in the revolutionary business. It was the start of the container revolution.

What are containers, exactly?

Containers are “self-contained units of software you can deliver from a server over there to a server over there, from your laptop to EC2 to a bare-metal giant server, and it will run in the same way because it is isolated at the process level and has its own file system,” as Hykes explained in his PyCon talk.

Docker soon established a de facto industry standard for containers by simplifying the procedure. Docker allows developers to deploy, replicate, relocate, and back up a workload in a streamlined manner, using reusable images to make workloads more portable and adaptable than previous techniques.

This could be accomplished in the virtual machine (VM) world by keeping applications distinct while running on the same hardware, but each VM has its own operating system, making them huge, sluggish to start, difficult to move around, and complex to manage and upgrade. Containers distinguished themselves from virtual machines (VMs) by isolating execution environments while sharing the underlying OS kernel, giving developers a lightweight and fast option.

Docker is made up of several elements.

Docker became popular among software developers because it pioneered a new way to package the tools needed to construct and launch a container in a more streamlined and straightforward manner than before feasible. Docker is made up of Dockerfile, container images, the Docker run utility, Docker Hub, Docker Engine, Docker Compose, and Docker Desktop, to name a few.

Dockerfile. A Dockerfile is the foundation of every Docker container. This text file contains instructions for creating a Docker image, including the operating system, languages, environmental variables, file locations, network ports, and any other components required for it to function.

Image created with Docker. A Docker image is a portable, read-only, executable file that contains the instructions for establishing a container as well as the specifications for which software components the container will run and how. It’s similar to a snapshot in the VM world.

Docker is a command-line tool for running Docker containers. The run command in Docker is used to start a container. Each container represents an image instance, and numerous instances of the same picture can run at the same time.

Docker Hub is a service that allows you to manage your Docker Docker Hub is a repository for storing, sharing, and managing container images. Consider it Docker’s own version of GitHub, but tailored to containers.

Docker Engine is a container management system. Docker Engine is the foundation of the Docker platform. The containers are created and run by the underlying client-server technology. The Docker Engine comes with a long-running daemon process named dockerd for container management, as well as APIs that allow programs to connect with the Docker daemon and a command-line interface.

Docker Compose is a container management system. Docker Compose is a command-line tool for defining and running multicontainer Docker applications using YAML files. It lets you create, start, stop, and rebuild all of the services in your setup, as well as check their status and log output.

Docker Desktop is a program that allows you to run Docker on Docker’s Desktop application wraps all of these component elements, making it easy to develop and share containerized apps and microservices.

Advantages of Docker

Docker containers make it possible to create programs that are easier to assemble, manage, and transfer around than before. Software engineers benefit from this in a number of ways.

Docker containers are small and lightweight, allowing for portability. Docker isolates programs and their environments to keep them clean and simple, allowing for more granular control and portability.

Docker containers provide for modularity. Containers make it easier for developers to assemble an application’s building blocks into a modular unit with easily interchangeable pieces, which can help developers speed up development cycles, feature releases, and issue patches.

Docker containers make scaling and orchestration easier. Because containers are lightweight, developers can launch a large number of them at once for improved service scaling. These container clusters must then be orchestrated, which is where Kubernetes often comes into play.
disadvantages of dockers

Containers solve a lot of difficulties, but they don’t solve all of the problems that developers face.

Containers in Docker are not virtual machines. Containers, unlike virtual machines, employ limited sections of the host operating system’s resources, which implies elements aren’t as isolated as they would be on a VM.

Docker containers don’t offer bare-metal performance. Containers are substantially lighter and closer to the metal than virtual machines, but they come at a cost in terms of performance. If your workload necessitates bare-metal performance, a container will let you get near but not quite there.

Docker containers are immutable and stateless. Containers start up and run from a picture that specifies what’s inside. By default, that image is immutable—it cannot be changed once it has been created. A container instance, on the other hand, is temporary. It’s gone for good once it’s been deleted from system memory. You must design for persistence if you want your containers to persist state across sessions, similar to a virtual machine.

What is Docker in today’s world?

Container adoption is increasing as cloud-native development methodologies become the de facto standard for developing and operating software, but Docker is no longer the only piece of the puzzle.

Docker got popular because it made moving an application’s code and all of its dependencies from a developer’s laptop to a server simple. However, the rise of containers has resulted in a shift in how applications are designed, from monolithic stacks to microservice networks. Many users soon required a mechanism to organize and manage large groups of containers.

The Kubernetes open source project, which was born out of Google, swiftly rose to the top as the best way to do so, eclipsing Docker’s own attempts to solve the problem with its Swarm orchestrator (RIP). Docker eventually sold its enterprise division to Mirantis in 2019, which has subsequently merged Docker Enterprise into the Mirantis Kubernetes Engine, despite mounting financial problems.

The surviving pieces of Docker—including the original open source Docker Engine container runtime, Docker Hub image repository, and Docker Desktop application—are led by industry veteran Scott Johnston, who wants to refocus the company on its core customer base of software professionals.