Docker is a set of platform as a service (PaaS) products that use operating-system-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries, and configuration files. This design ensures they can run consistently and reliably anywhere, regardless of the underlying infrastructure (Linux, Windows, macOS, or cloud environments).


Docker was initially released in 2013 by Docker, Inc. (originally dotCloud) and has become one of the most popular tools for containerization. Its rapid adoption accelerated the use of microservices architectures and streamlined software development processes.

Key Concepts

  • Images: Docker images are read-only templates used to create containers. They contain instructions for building a complete, runnable software environment.
  • Containers: Docker containers are the running instances of images. They are lightweight, portable, and can be started or stopped quickly.
  • Docker Engine: The core software component that manages containers, images, and other Docker objects. It consists of a server daemon (dockerd) and a command-line interface client (docker).
  • Docker Hub: A public repository of Docker images, both official and community-created. Developers can share and find pre-built images for many popular applications and software stacks.

Use Cases

  • Microservices: Docker simplifies the development and deployment of microservices by isolating individual components within containers.
  • DevOps and CI/CD: Docker streamlines continuous integration and continuous delivery pipelines by enabling consistent and reproducible builds and deployments.
  • Hybrid-cloud environments: Docker's portability allows applications to run seamlessly across on-premises servers, cloud providers, or a combination of both.
  • Legacy application modernization: Docker can be used to package and run older applications in a modern environment, enhancing portability and maintainability.

Technical Details

Docker leverages Linux kernel features like namespaces and cgroups to isolate processes and resources within containers. This differs from traditional virtual machines that run a complete guest operating system within each VM, resulting in greater overhead.


  • Portability: Build applications once and run them anywhere Docker supports.
  • Efficiency: Containers have a smaller footprint and lower resource overhead compared to VMs.
  • Scalability: Easily scale applications up or down based on demand.
  • Developer productivity: Docker simplifies the process of setting up and managing development environments.

Getting Started

  1. Install Docker: Refer to Docker’s website for installation instructions for your OS.
  2. Build an image: Create a Dockerfile to define your image's structure.
  3. Run a container: Use the docker run command to create a running instance from your image.

Community and Ecosystem

Docker has a large, active open-source community with extensive documentation, tutorials, and online resources. Many complementary technologies enhance its functionality:

  • Kubernetes: Container orchestration platform for automating deployment, scaling, and management of applications.
  • Docker Compose: A tool for defining and running multi-container Docker applications.