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🚀 Docker Quick Start Guide

A simplified reference for getting started with Docker: from installation, pulling images, running containers, and publishing to Docker Hub.

📥 Installation

Install Docker from the official site:
👉 https://docs.docker.com/get-docker/

Verify installation:

docker --version
docker info

📦 Pulling and Managing Docker Images

docker pull <image_name>       # Download image from Docker Hub
docker images                  # List all downloaded images

Example:

docker pull hello-world

🏃 Running Containers

docker run <image_name>        # Runs a new container
docker run -it <image_name>    # Runs interactively

Each run creates a new container with a random ID and name.

📋 Viewing Containers

docker ps                      # Show running containers
docker ps -a                   # Show all containers (running + stopped)

🧱 Container Management

docker start <container_id|name>     # Start a container
docker stop <container_id|name>      # Stop a container
docker rename old_name new_name      # Rename a container
docker rm <container_id|name>        # Remove a stopped container
docker container prune               # Remove all stopped containers

🔄 Running Commands in Containers

docker exec -it <container_id|name> <command>  # Run command inside container
docker exec -it my_container node              # Start Node.js shell
docker exec -it my_container /bin/bash         # Access Linux shell

📁 Copying Files

From Host to Container

docker cp ./example.txt <container_name>:/example.txt

From Container to Host

docker cp <container_name>:/example.txt ./copied.txt

Use cat <filename> inside the container to view file contents.

📄 Building Docker Images

Dockerfile Example:

FROM alpine:latest
CMD ["echo", "Hello, Docker"]

Build Image

docker build -t my_custom_image .

🗃️ Docker Volumes (Data Persistence)

docker volume create my_volume
docker run -v my_volume:/data alpine
docker volume ls

Volumes allow data to persist even after a container is deleted.

📦 Docker Compose (Multi-Container Apps)

Create a docker-compose.yml file:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "80:80"

Start with:

docker-compose up

Stop with:

docker-compose down

🚫 Ignoring Files: .dockerignore

Create a .dockerignore file to exclude files/folders from the image:

node_modules
*.log
Dockerfile

📤 Docker Hub: Push Image

  1. Login:
docker login
  1. Tag the image:
docker tag my_image <username>/<repository>:latest
  1. Push the image:
docker push <username>/<repository>:latest
  1. Pull from anywhere:
docker pull <username>/<repository>:latest

🏢 Docker Registry

A Docker registry is a system for storing and distributing Docker images.

  • Docker Hub is the default public registry.
  • Run your own private registry:
docker run -d -p 5000:5000 --name registry registry:2

🛡️ Best Practices

  • Use lightweight base images (like alpine)
  • Use multi-stage builds for production apps
  • Clean up unused packages in Dockerfile
  • Tag images clearly (e.g., :v1, :latest, :prod)
  • Use .dockerignore to reduce image size and build time

✅ Useful Summary Commands

Action Command
List Images docker images
Run Container docker run <image>
List Containers docker ps -a
Build Image docker build -t name .
Exec into Container docker exec -it <id> bash
Copy Files docker cp
Push to Docker Hub docker push