Docker Architecture Overview

We all know what docker is and we do use it in our cloud native applications but do we know whats the internal structure of docker and how does it manage the containerization responsibility.

Lets explore that…

Docker Architecture

Docker’s architecture is composed of several key components that work together to facilitate the creation, deployment, and management of containerized applications. Understanding these components is essential for effectively using Docker.

1. Docker Engine

The Docker Engine is the core component of Docker, responsible for creating, running, and managing containers. It comprises three main parts:

• Docker Daemon (dockerd): This is the background service running on the host machine. It is responsible for managing Docker objects (e.g., images, containers, networks, and volumes). The daemon listens for Docker API requests and processes them.
• Docker Client (docker): This is the command-line interface (CLI) that users interact with. The Docker Client sends commands to the Docker Daemon via Docker API, either on the same host or a remote one. For instance, when you run docker run, the client communicates this command to the daemon.
• REST API: The Docker API is a RESTful interface used by the Docker Client and other programs to communicate with the Docker Daemon. It provides access to Docker’s functionality programmatically.

2. Docker Objects

Docker uses several types of objects to run applications:

• Images: Docker images are read-only templates used to create containers. They contain the application code, runtime, libraries, environment variables, and configuration files required to run the application. Images are built from Dockerfiles.
• Containers: Containers are runnable instances of Docker images. They encapsulate everything needed to run the application, including the code, runtime, system tools, libraries, and settings. Containers are isolated from each other and the host system, ensuring consistent environments across different stages of development.
• Networks: Docker networks enable communication between containers. Docker provides several types of networks (e.g., bridge, host, overlay) to suit different use cases and configurations.
• Volumes: Volumes are used for persistent storage in Docker. They allow data to persist even when containers are stopped or deleted. Volumes can be shared between multiple containers.

3. Docker Hub

Docker Hub is a cloud-based repository service where users can create, share, and store Docker images. It acts as a centralized resource for discovering and distributing Docker images. Users can push their custom images to Docker Hub and pull official or community images from it.

• Public Repositories: These are accessible by anyone and can be freely used and shared.
• Private Repositories: These are restricted and only accessible to specified users or teams, providing greater control over who can access and use the images.

4. Docker Compose

Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services, networks, and volumes. You can then use a single command to create and start all the services from your configuration.

• docker-compose.yml: This file defines the services, networks, and volumes for a multi-container Docker application. It specifies the image to use, environment variables, dependencies, and other configurations.
• Commands: Common commands include docker-compose up to start the application and docker-compose down to stop and remove the containers, networks, and volumes defined in the docker-compose.yml file.

5. Docker Swarm

Docker Swarm is Docker’s native clustering and orchestration tool. It allows you to manage a cluster of Docker nodes as a single virtual system, enabling scalability and redundancy.

• Swarm Mode: When Docker is in swarm mode, you can deploy services that span multiple Docker nodes. Swarm mode includes features like service discovery, load balancing, scaling, and desired state management.
• Services and Tasks: In Docker Swarm, a service is the definition of the desired state for a group of containers, and a task is a container managed by the swarm to fulfill the service requirements.

Happy Learning :)