Docker is composed of several key components that work together to create, manage, and run containerized applications. Here are the main components of Docker:
- Docker Engine: Docker Engine is the core component of Docker. It is a client-server application consisting of a daemon process (dockerd) running on the host machine and a command-line interface (CLI) tool (docker) used to interact with the daemon. The Docker Engine is responsible for building, managing, and running Docker containers.
- Docker Daemon (dockerd): The Docker daemon (dockerd) is a background process running on the host machine responsible for managing Docker objects such as containers, images, networks, and volumes. It listens for Docker API requests and executes them, handling container lifecycle management, image handling, and more.
- Docker Client (docker): The Docker client (docker) is a command-line interface (CLI) tool used by users to interact with the Docker daemon. It allows users to build, run, manage, and monitor Docker containers and images through a set of commands and options. Users can use the Docker client to perform various tasks such as creating containers, pulling images from registries, and inspecting container logs.
- Docker Images: Docker images are read-only templates used to create Docker containers. An image contains the application code, runtime, libraries, dependencies, and other files needed to run the application. Images are built from a Dockerfile, which specifies the instructions for creating the image layers. Images can be stored locally or pushed to a container registry for sharing and distribution.
- Docker Containers: Docker containers are lightweight, portable, and self-contained runtime environments created from Docker images. Each container encapsulates an application along with its dependencies, ensuring consistency and isolation from the host system and other containers. Containers run as isolated processes on the host machine and can be started, stopped, paused, and deleted using Docker commands.
- Docker Registries: Docker registries are centralized repositories used to store and distribute Docker images. Docker Hub is the official public registry maintained by Docker, containing millions of publicly available images. Additionally, organizations can set up private registries to store their custom-built images securely. Docker users can push, pull, and search for images from registries using Docker commands.
- Docker Volumes: Docker volumes are persistent storage mechanisms used to persist data generated by Docker containers. Volumes allow data to be shared between containers, preserved across container restarts, and managed independently of container lifecycle. Docker volumes can be created and attached to containers to store configuration files, databases, logs, and other application data.
- Docker Networks: Docker networks provide networking capabilities for connecting Docker containers to each other and to external networks. Docker supports various network drivers for different networking scenarios, including bridge networks for connecting containers on the same host, overlay networks for connecting containers across multiple hosts, and host networks for directly exposing container ports on the host network.
These key components work together to enable the development, deployment, and management of containerized applications using Docker.
