Docker 101

References: Docker Official Docs

What is Docker?

A platform-as-a-service that creates isolated virtualization environments for building, implementing, and testing applications
When using Docker, you can separate applications from infrastructure to run software quickly

Docker uses a client-server architecture.
Docker client communicates with Docker Daemon which performs heavy tasks like building, running, and deploying Docker Containers.
Uses Linux Kernel features to create Containers on top of the operating system, and Docker itself runs as a Daemon that manages service Containers.
The Docker server is the entity that actually creates Containers and manages Images, and operates in the Docker engine process.
Docker engine receives API input from outside and performs Docker engine functions.
The state where Docker process is running and ready to receive input as a server is called Docker Daemon
When you enter commands starting with docker, you're using the Docker client.
Docker client passes the entered commands as API to the Docker Daemon that exists locally
At this time, Docker client calls Docker Daemon's API through a socket located at /var/run/docker.sock

Provides functionality to deliver applications in consistent, standardized form like containers used in actual cargo ships
Provides functionality to package and run applications in loosely isolated environments
Can run multiple Containers simultaneously on a specified host through isolation and security
Lightweight and includes everything needed to run applications, so no need to depend on items installed on the host. In other words, everyone gets the same Container that works the same way
Therefore, Docker allows developers to work in standardized environments using local Containers that provide applications and services.
Containers are also suitable for CI/CD workflows

Receives Docker API requests and manages Docker objects such as Images, Containers, networks, and volumes.
Daemon can also communicate with other Daemons to manage Docker services.

Used for packaging and transporting applications.
Includes independent environment needed to run applications, and can be seen as a kind of template for runtime environment.
It's an immutable file that includes source code, libraries, dependencies, tools, and other files needed to run applications.
Images are read-only, so they're also called snapshots, representing applications and virtual environments at a specific point in time.
This consistency is one of Docker's major features, allowing developers to test and experiment with software in stable and uniform environments

Last updated 6 days ago