Docker is an open source software platform used to create, deploy and manage virtualized application containers on a common operating system (OS), with an ecosystem of allied tools. Docker gives software developers a faster and more efficient way to build and test containerized portions of an overall software application. This lets developers in a team concurrently build multiple pieces of software. 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.
Continuously deploying software: Docker technology and strong DevOps practices make it possible to deploy containerized applications in a few seconds, unlike traditional bulky, monolithic applications that take much longer. Updates or changes made to an application's code are implemented and deployed quickly when using containers that are part of a larger continuous integration/continuous delivery pipeline.
Building a microservice-based architecture: When a microservice-based architecture is more advantageous than a traditional, monolithic application, Docker is ideal for the process of building out this architecture. Developers build and deploy multiple microservices, each inside their own container. Then they integrate them to assemble a full software application with the help of a container orchestration tool, such as Docker Swarm.
Migrating legacy applications to a containerized infrastructure: A development team wanting to modernize a preexisting legacy software application can use Docker to shift the app to a containerized infrastructure.
Enabling hybrid cloud and multi-cloud applications: Docker containers operate the same way whether deployed on premises or using cloud computing technology. Therefore, Docker lets applications be easily moved to various cloud vendors' production and testing environments. A Docker app that uses multiple cloud offerings can be considered hybrid cloud or multi-cloud.
Docker Community Edition is open source, while Docker Enterprise Edition is a commercialized version offered by Docker Inc. Docker consists of various components and tools that help create, verify and manage containers.
The Docker Engine is the underlying technology that handles the tasks and workflows involved in building container-based applications. The engine creates a server-side daemon process that hosts images, containers, networks and storage volumes.
The daemon also provides a client-side command-line interface (CLI) for users to interact with the daemon through the Docker application programming interface. Containers created by Docker are called Dockerfiles. Docker Compose files define the composition of components in a Docker container.
Other components and tools in the docker architecture include the following:
Docker Hub: This software-as-a-service tool lets users publish and share container-based applications through a common library. The service has more than 100,000 publicly available applications as well as public and private container registries.
Trusted Registry: This is a repository that's similar to Docker Hub but with an extra layer of control and ownership over container image storage and distribution.
Docker Swarm: This is part of the Docker Engine that supports cluster load balancing for Docker. Multiple Docker host resources are pooled together in Swarm to act as one, which lets users quickly scale container deployments to multiple hosts.
Universal Control Plane: This is a web-based, unified cluster and application management interface.
Compose: This tool is used to configure multicontainer application services, view container statuses, stream log output and run single-instance processes.
Content Trust: This security tool is used to verify the integrity of remote Docker registries, through user signatures and image tags.
