Docker Basics: Concepts, Architecture, Installation, and Usage

Docker is a Linux container technology that packages applications with their dependencies into lightweight, portable images, enabling consistent deployment across environments.

Unlike traditional virtual machines, containers share the host kernel and hardware resources, providing faster startup, lower overhead, and finer resource control.

The Docker architecture follows a client‑server model: the Docker client sends commands to the Docker daemon, which builds, runs, and distributes images via the Docker Registry.

Key components include Docker Client, Docker Daemon, Docker Image, Docker Container, and Docker Registry. Images are read‑only layers combined with a writable layer to form a running container.

Installation on CentOS 7 involves removing old Docker packages, installing dependencies, and using either the package manager or the official installation script:

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

curl -fsSL https://get.docker.com -o get-docker.sh
sh get-docker.sh

After installation, enable and start the service:

sudo systemctl enable docker
sudo systemctl start docker

Basic Docker commands demonstrated include docker pull , docker images , docker run , docker ps , docker start , docker stop , docker rm , and docker rmi .

A Dockerfile defines how to build an image using instructions such as FROM , MAINTAINER , COPY , WORKDIR , RUN , EXPOSE , ENTRYPOINT , and CMD . An example builds a simple Nginx image that serves a custom HTML page.

Overall, the guide provides a step‑by‑step introduction to Docker concepts, architecture, installation, common commands, and Dockerfile usage for creating reproducible containerized environments.