What Is Docker? Understanding Containers and Their Role in Cloud‑Native Computing

Docker Is Hot: Statistics and Overview

In just four months after its launch, Docker has been downloaded over 50,000 times, received more than 4,000 stars on GitHub, attracted over 100 contributors, and is used by more than 150 projects and 1,000 products.

The most striking fact is that before Docker reached a stable release, companies such as Red Hat and AWS already provided official support, and many developers and enterprises rushed to run it in production, prompting Docker’s CEO to urge patience because the platform was not yet ready.

Back in August 2014, only a year after Docker’s initial release, I talked with a large media R&D center in Hunan; their developers were already using Docker in production, and over the next two years every client I met—from C‑level executives to middle managers and developers—kept bringing up Docker.

What exactly is Docker? What is a container?

Docker and Containers

Docker (literal translation: dock worker) is the worker who moves cargo at a dock.

Container (English: container) can be translated back as either a shipping container or a generic container.

If we follow the everyday analogy, Docker (the dock worker) moves containers (the shipping boxes). For programmers, Docker is the “code‑container mover” and the container is the packaged application itself.

Docker and containers are distinct: Docker is the tool that assembles, transports, and unpacks containers. It is essentially a utility that builds, pushes/pulls, and runs the packaged applications, while the container is the package itself.

What Is a Container?

A container is similar to a shipping container: it bundles code and everything needed to run it so that it can be moved from point A to point B without mixing with other programs. The concept has existed since the early days of computing, but Docker made its use extremely simple. In Unix/Linux this was once called a Process Container, now known as a Control Group (cGroup); in Windows there were similar components. All aim to transport an application while keeping it isolated.

Docker is not the same as a container—one is the worker, the other is the cargo. Yet many technical articles and talks conflate the two, which is why this article clarifies the distinction.

Docker, Containers, and Virtual Machines

Comparisons between Docker and virtual machines are like comparing apples and bananas; they are fundamentally different technologies. The comparison is often made to help non‑technical managers understand why additional spending on containers is needed after investing in virtualization platforms.

Containers start quickly because they only launch the application process, whereas virtual machines load an entire operating system, which is slower. However, you still need a hypervisor (Hyper‑V, VMware, KVM) to run containers, so the performance gain is not absolute.

Why Use Docker?

Docker’s advantage is that it packages an application together with all its dependencies into a single “container”. When the container arrives, you can unpack it and run the application without hunting for missing libraries or environment settings—much like receiving a ready‑to‑cook meal with all ingredients included.

Docker also handles the logistics: you pull images from Docker Hub, run them on any host with an OS, and the application starts instantly.

In one sentence, Docker is a tool and ecosystem that optimizes the application operation and delivery process.

Enjoy your dinner!

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docker4dotnet #5: Building a Container‑Based Continuous Delivery Pipeline with VSTS/TFS

Explorations of DevOps with Docker

Using Docker for CI: Answers to Common Questions