Docker Primer

Docker is an open-source platform that simplifies the process of building, deploying, and running applications in containers. Containers are lightweight, portable, and self-contained environments that package an application, along with its dependencies, libraries, and runtime, to ensure consistent behavior across different platforms and environments.

Main concepts and components of Docker:

Docker Engine: The core component of Docker, responsible for creating and managing containers. It runs on the host operating system and communicates with the Docker client using a REST API.

Dockerfile: A script containing instructions to build a Docker image. It defines the base image, application source code, dependencies, and configurations required to create a containerized application.

Docker Image: A read-only template used to create Docker containers. Images are created from Dockerfiles and stored in a registry, such as Docker Hub or a private registry.

Docker Container: A lightweight, portable, and self-contained environment created from a Docker image. Containers run the application and its dependencies, isolated from the host system and other containers.

Docker Hub: A public registry for sharing and distributing Docker images. It provides a centralized platform for developers to store, manage, and share container images.

Docker Compose: A tool for defining and running multi-container Docker applications. It uses a YAML file (docker-compose.yml) to configure the application’s services, networks, and volumes.

Basic Commands

Here are some basic Docker commands that are essential when working with Docker:

  1. Build an image: Build a Docker image from a Dockerfile in the current directory.

docker build -t image-name:tag .

  1. List images: Display a list of Docker images available on your local system.

docker images

  1. Run a container: Create and start a new Docker container from an image.

docker run -d -p host-port:container-port --name container-name image-name:tag
-d: Run the container in detached mode (in the background).
-p: Map the host port to the container port.
--name: Assign a name to the container for easier reference.

  1. List containers: Show a list of all running containers.

docker ps

To list all containers, including stopped ones, use:

docker ps -a

  1. Stop a container: Stop a running container.

docker stop container-name-or-id

  1. Start a container: Start a stopped container.

docker start container-name-or-id

  1. Remove a container: Delete a stopped container.

docker rm container-name-or-id

  1. Remove an image: Delete a Docker image from your local system.

docker rmi image-name:tag

  1. Container logs: Display logs from a running container.

docker logs container-name-or-id

  1. Execute a command inside a container: Run a command within a running container.

docker exec -it container-name-or-id command

For example, to open a shell inside a running container, use:

docker exec -it container-name-or-id /bin/bash

  1. Pull an image: Download a Docker image from a registry (e.g., Docker Hub).

docker pull image-name:tag

  1. Push an image: Upload a Docker image to a registry (e.g., Docker Hub). Make sure you are logged in with docker login and the image is tagged with your username.

docker push username/image-name:tag

To get started with Docker, follow these steps:

  1. Install Docker: Download and install Docker for your operating system from the official website (https://www.docker.com/get-started).

  2. Use the provided dockerfile in the repository