Master Docker from Scratch: The Ultimate Beginner-to-Expert Guide

Docker Overview

Docker is a client‑server platform that uses container technology to package applications and their dependencies, offering lightweight, fast, and portable deployment compared to traditional virtual machines.

Key Benefits

Lightweight compared to VMs

Fast startup (seconds vs minutes)

Efficient resource utilization

Easy scaling and versioning

Installation

Instructions for installing Docker on CentOS 8, including removing old versions, adding the Docker repository, installing packages, starting the daemon, and verifying with docker version.

# yum remove docker ...
# yum install -y yum-utils
# yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
# yum install docker-ce docker-ce-cli containerd.io
# systemctl start docker
# docker version

Basic Commands

Common Docker commands for images, containers, and system information.

docker images          # list images
docker pull mysql:5.7   # download image
docker run -d -p 8080:80 nginx   # run container
docker ps -a           # list all containers
docker exec -it <container> /bin/bash   # enter container
docker rm -f <id>     # remove container

Images and Layers

Docker images are built from read‑only layers using UnionFS; each command in a Dockerfile creates a new layer, enabling sharing of common base layers.

Dockerfile

A Dockerfile defines how to build an image. Example commands include FROM, RUN, COPY, ENV, EXPOSE, CMD, and ENTRYPOINT.

FROM centos:7
MAINTAINER [email protected]
RUN yum -y install vim net-tools
WORKDIR /usr/local
ENV MYPATH /usr/local
CMD ["/bin/bash"]

Data Volumes

Volumes persist data beyond container lifetimes and can be shared between containers. Use -v host_path:container_path or named volumes.

docker run -d -v /home/data:/var/lib/mysql mysql:5.7

Networking

Docker creates a default bridge network (docker0) with automatic IP assignment. For name‑based communication, create user‑defined bridge networks.

docker network create --driver bridge mynet
docker run --net mynet --name app1 nginx
docker run --net mynet --name app2 nginx

Practical Examples

Examples include deploying a simple Nginx service, running MySQL with a persistent volume, and linking containers for inter‑service communication.