Docker Basics Guide

This guide provides a quick reference for getting started with Docker on Ubuntu. Docker is a platform for developing, shipping, and running applications in containers.

Table of Contents

1. Installing Docker
2. Running Your First Container
3. Building Docker Images
4. Dockerfile Basics
5. Managing Docker Containers
6. Networking with Docker
7. Data Management with Docker Volumes
8. Docker Compose
9. Docker Hub and Registry
10. Docker Cleanup

1. Installing Docker

Install Docker on Ubuntu:

sudo apt update
sudo apt install docker.io
sudo usermod -aG docker $USER

Logout and login to apply group changes.

2. Running Your First Container

Run a simple hello-world container to test the installation:

docker run hello-world

3. Building Docker Images

Create a Dockerfile and build a custom image:

# Dockerfile
FROM ubuntu:latest
RUN apt update && apt install -y nginx
CMD ["nginx", "-g", "daemon off;"]

Build the image:

docker build -t my-nginx-image .

4. Dockerfile Basics

• FROM: Specifies the base image.
• RUN: Executes commands during image build.
• CMD or ENTRYPOINT: Specifies the default command to run when the container starts.

5. Managing Docker Containers

• docker ps: List running containers.
• docker ps -a: List all containers (including stopped ones).
• docker stop : Stop a running container.
• docker start : Start a stopped container.
• docker rm : Remove a stopped container.

6. Networking with Docker

• docker network ls: List Docker networks.
• docker network create : Create a new network.
• docker run --network= ...: Connect a container to a network.

7. Data Management with Docker Volumes

• docker volume ls: List Docker volumes.
• docker volume create : Create a new volume.
• Use volumes to persist data between container restarts.

8. Docker Compose

Create a docker-compose.yml file for multi-container applications:

version: '3'
services:
  web:
    image: nginx:latest
  db:
    image: postgres:latest

Run the services:

docker-compose up

9. Docker Hub and Registry

• Create a Docker Hub account: Docker Hub
• Tag your local image: docker tag my-nginx-image username/my-nginx-image
• Push to Docker Hub: docker push username/my-nginx-image

10. Docker Cleanup

• docker system prune: Remove unused data (containers, networks, volumes, etc.).
• docker image prune: Remove dangling images.

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