Docker Basics: Containers, Images, Commands, and Practical Usage

Docker, a popular container technology since 2013, packages software into standardized units for development, delivery, and deployment.

Containers differ from virtual machines by sharing the host OS kernel, offering faster startup, lower resource usage, and smaller size.

Key Docker concepts are Image, Container, and Repository; images are layered filesystems, containers are runtime instances, and repositories store images.

Typical Docker workflow includes installing Docker, pulling images (e.g., docker pull ubuntu:18.04), listing images ( docker images), creating and starting containers ( docker create --name myc ubuntu:18.04, docker start myc), executing commands inside containers ( docker exec -it myc bash), and committing changes to new images ( docker commit -m "add node" myc myimage:v1).

Images can be pushed to registries ( docker login, docker push myrepo/myimage:tag) and built automatically with a Dockerfile that starts with FROM base_image and contains instructions such as RUN apt-get update && apt-get install -y nginx.

The article also shows practical examples for installing Docker on Ubuntu, managing containers, and creating custom images for PHP, MySQL, and other services.