What Is Docker? Objects, Tools & Workflow Explained

The OCI consists of leading companies, including Docker, IBM and Red Hat®. It supports innovation while helping organizations avoid vendor lock-in. They can also download predefined base images from the Docker filesystem as a starting point for any containerization project. Building Docker images from scratch is possible, but most developers pull them down from common repositories. Developers can create multiple Docker images from a single base image and will share their stack’s commonalities. Docker is the most widely used containerization tool, with an 82.84% market share.4 Docker is so popular today that “Docker” and “containers” are used interchangeably.

  • Developer teams mainly use Docker to create distributed applications that work efficiently in different environments.
  • Times have changed, though, and instead of focusing on single servers, the Internet is built upon arrays of inter-dependent and redundant servers in a system commonly called “the cloud”.
  • Instead of adding new layers to an image, a better solution to preserve data produced by a running container is using Docker volumes.
  • The platform allows users to ship their applications anywhere quickly, collaborate with teammates, and automate builds for faster integration to a development pipeline.

It contains all the necessary code, runtime, system tools, libraries, and settings required to run a software application. It provides features such as you can push your images as private or public registry where you can store and share Docker images. Linux containers have facilitated a massive shift docker what is it in high-availability computing. There are many toolsets out there to help you run services, or even your entire operating system, in containers. The Open Container Initiative (OCI) is an industry standards organization that encourages innovation while avoiding the danger of vendor lock-in.

Docker overview

Images are immutable (i.e., they cannot be changed), so any modification in the structure and content requires creating a new Docker image. To get the most out of your Docker workflows, you need effective automation. CircleCI’s industry-leading CI/CD platform is purpose-built to help you capture the benefits of containerization throughout your development cycle. Understanding these terms and how they interrelate is crucial for leveraging Docker’s full potential in application development and deployment. Runnable instances of Docker images that encapsulate the application and its environment, providing an isolated environment for the application to run.

What Is Docker

With Docker Compose, each container is constructed to run on a single host. There are third-party tools that work with Docker for tasks such as container management and clustering. Docker competes with proprietary application containers such as the VMware vApp and infrastructure abstraction tools, including Chef.

The Docker platform

This immutability ensures consistency and reproducibility in application deployment. Imagine you need to build multiple shipping containers to transport items all over the world. You start with a document listing out the requirements for your shipping container.

What Is Docker

Offload tedious and repetitive tasks involving security management, compliance management, deployment management and ongoing lifecycle management. Use IBM Cloud Satellite to start consistent cloud services anywhere—on premises, at the edge and in public cloud environments. Docker images are made up of layers, and each layer corresponds to a version of the image. Whenever a developer makes changes to an image, a new top layer is created, and this top layer replaces the previous top layer as the current version of the image. Previous layers are saved for rollbacks or to be reused in other projects. While LXC containers often reference machine-specific configurations, Docker containers run without modification across any desktop, data center or cloud computing environment.

What is needed to use Docker Hub?

Each container contains all elements needed to build a software component and ensure it’s built, tested and deployed smoothly. Docker enables portability for when these packaged containers are moved to different servers or environments. According to Statista, more than 85% of large global organizations use microservices for their application development11. Docker simplifies app deployment as each microservice can be containerized and independently scaled and managed, thus eliminating the need for developers to configure and manage particular environments. In contrast to the traditional monolithic approach of a large, tightly coupled application, microservices provide a cloud-native architectural framework.

It is a file, comprised of multiple layers, used to execute code in a Docker container. Docker Image is an executable package of software that includes everything needed to run an application. This image informs how a container should instantiate, determining which software components will run and how. Docker Container is a virtual environment that bundles application code with all the dependencies required to run the application. The application runs quickly and reliably from one computing environment to another. Docker Desktop provides GUI to work on docker containers, docker images and docker networks.

Docker security

Virtual Machines (VMs) run on Hypervisors, which allow multiple Virtual Machines to run on a single machine along with its own operating system. Security was also the main selling point for Docker alternatives, particularly CoreOS’ rkt, pronounced rocket. However, Docker has made strides to improve its security options while, at the same time, momentum for those container alternatives has faded. In recent years, Docker was supplanted by Kubernetes for container orchestration. However, most Kubernetes offerings actually run Docker behind the scenes. Developers can also use Docker Compose to define persistent volumes for storage, specify base nodes and document and configure service dependencies.

Docker Compose files define the composition of components in a Docker container. Docker uses resource isolation in the OS kernel to run multiple containers on the same OS. This is different than virtual machines (VMs), which encapsulate an entire OS with executable code on top of an abstracted layer of physical hardware resources. Containers as a service (CaaS) enables developers to manage and deploy containerized applications, making it easy to run Docker containers at scale. All the major CSPs offer CaaS as part of their cloud services portfolios, along with infrastructure as a service (IaaS), software as a service (SaaS), and so forth.

If this explanation still causes you to scratch your head, consider the following analogy using shipping containers. So, a Dockerfile is used to build a Docker Image which is then used as the template for creating one or more Docker containers. A Dockerfile contains the set of instructions for building a Docker Image.

What Is Docker

Developers can access an open source registry containing thousands of user-contributed containers. Docker works with all development tools such as VS Code, CircleCI, and GitHub. The following command runs an ubuntu container, attaches interactively to your
local command-line session, and runs /bin/bash.

Get started with the basics with our guide to containers, including what they are, their advantage over virtual machines, and more. Develop your own unique applications with Docker images and create multiple containers using Docker Compose. Docker is written in the
Go programming language and takes
advantage of several features of the Linux kernel to deliver its functionality. Docker uses a technology called namespaces to provide the isolated workspace
called the container. When you run a container, Docker creates a set of
namespaces for that container.

What Is Docker

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