Docker Preview

Docker packages applications with everything they need to run. No more "it works on my machine." Same container runs anywhere.

Why Containers?

Traditional approach:

Install OS
Install dependencies (exact versions!)
Configure environment
Hope nothing conflicts
Repeat for every server

Container approach:

Build container once
Run anywhere

Install Docker

Terminal

$# Install Docker

$curl -fsSL https://get.docker.com | sh

Installing Docker...

$# Add your user to docker group

$sudo usermod -aG docker $USER

$# Log out and back in, then verify

$docker --version

Docker version 24.0.7, build afdd53b

Run Your First Container

Terminal

$docker run hello-world

Unable to find image 'hello-world:latest' locally latest: Pulling from library/hello-world ... Hello from Docker! This message shows that your installation appears to be working correctly.

That pulled an image and ran it as a container.

Core Concepts

Term	Meaning
Image	Blueprint/template (like a class)
Container	Running instance (like an object)
Dockerfile	Instructions to build an image
Registry	Image storage (Docker Hub)

Run Useful Containers

Run nginx

Terminal

$docker run -d -p 8080:80 nginx

a1b2c3d4e5f6...

$curl localhost:8080

<!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title>

-d runs in background (detached)
-p 8080:80 maps host port 8080 to container port 80

List Containers

Terminal

$docker ps

CONTAINER ID IMAGE COMMAND STATUS PORTS a1b2c3d4e5f6 nginx "/docker-entrypoint.…" Up 2 minutes 0.0.0.0:8080->80/tcp

Stop and Remove

Terminal

$docker stop a1b2c3d4e5f6

$docker rm a1b2c3d4e5f6

$# Or stop and remove together

$docker rm -f a1b2c3d4e5f6

Build Your Own Image

Create a Dockerfile:

hljs dockerfile

FROM node:20-alpine

WORKDIR /app

COPY package*.json ./
RUN npm install

COPY . .

EXPOSE 3000
CMD ["node", "server.js"]

Build and run:

Terminal

$docker build -t myapp .

Building...

$docker run -d -p 3000:3000 myapp

Docker Compose

Manage multi-container apps with docker-compose.yml:

hljs yaml

version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://db:5432/myapp
    depends_on:
      - db

  db:
    image: postgres:15
    environment:
      POSTGRES_DB: myapp
      POSTGRES_PASSWORD: secret
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data:

Terminal

$docker compose up -d

Creating network... Creating myapp_db_1... Creating myapp_web_1...

$docker compose logs -f web

(view logs)

$docker compose down

(stop everything)

Essential Commands

Terminal

$# List images

$docker images

REPOSITORY TAG IMAGE ID SIZE nginx latest a1b2c3d4e5f6 142MB node 20 b2c3d4e5f6g7 1.1GB

$# List all containers

$docker ps -a

$# View container logs

$docker logs container_id

$# Shell into running container

$docker exec -it container_id /bin/sh

$# Clean up unused images

$docker system prune -a

When to Use Docker

Good for:

Consistent development environments
Deploying applications
Running databases locally
CI/CD pipelines
Microservices

Overkill for:

Simple scripts
Learning Linux basics first
When native install is simpler

Learn Docker Properly

This is just a preview. Docker deserves its own course. Once you're comfortable with Linux basics, dive deeper into containers.

Knowledge Check

What's the difference between a Docker image and container?

Quick Reference

Command	Purpose
`docker run -d -p 80:80 img`	Run container
`docker ps`	List running containers
`docker stop id`	Stop container
`docker rm id`	Remove container
`docker images`	List images
`docker build -t name .`	Build image
`docker compose up -d`	Start compose services
`docker compose down`	Stop compose services
`docker logs id`	View logs
`docker exec -it id sh`	Shell into container

Key Takeaways

Images are templates, containers are running instances
-d for background, -p for port mapping
Dockerfile defines how to build an image
Docker Compose manages multi-container apps
Containers solve "works on my machine" problems
Learn Linux basics before diving deep into Docker

Next: security fundamentals.

Docker Preview

Docker packages applications with everything they need to run. No more "it works on my machine." Same container runs anywhere.

Why Containers?

Traditional approach:

Install OS
Install dependencies (exact versions!)
Configure environment
Hope nothing conflicts
Repeat for every server

Container approach:

Build container once
Run anywhere

Install Docker

Terminal

$# Install Docker

$curl -fsSL https://get.docker.com | sh

Installing Docker...

$# Add your user to docker group

$sudo usermod -aG docker $USER

$# Log out and back in, then verify

$docker --version

Docker version 24.0.7, build afdd53b

Run Your First Container

Terminal

$docker run hello-world

Unable to find image 'hello-world:latest' locally latest: Pulling from library/hello-world ... Hello from Docker! This message shows that your installation appears to be working correctly.

That pulled an image and ran it as a container.

Core Concepts

Term	Meaning
Image	Blueprint/template (like a class)
Container	Running instance (like an object)
Dockerfile	Instructions to build an image
Registry	Image storage (Docker Hub)

Run Useful Containers

Run nginx

Terminal

$docker run -d -p 8080:80 nginx

a1b2c3d4e5f6...

$curl localhost:8080

<!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title>

-d runs in background (detached)
-p 8080:80 maps host port 8080 to container port 80

List Containers

Terminal

$docker ps

CONTAINER ID IMAGE COMMAND STATUS PORTS a1b2c3d4e5f6 nginx "/docker-entrypoint.…" Up 2 minutes 0.0.0.0:8080->80/tcp

Stop and Remove

Terminal

$docker stop a1b2c3d4e5f6

$docker rm a1b2c3d4e5f6

$# Or stop and remove together

$docker rm -f a1b2c3d4e5f6

Build Your Own Image

Create a Dockerfile:

hljs dockerfile

FROM node:20-alpine

WORKDIR /app

COPY package*.json ./
RUN npm install

COPY . .

EXPOSE 3000
CMD ["node", "server.js"]

Build and run:

Terminal

$docker build -t myapp .

Building...

$docker run -d -p 3000:3000 myapp

Docker Compose

Manage multi-container apps with docker-compose.yml:

hljs yaml

version: '3.8'

services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://db:5432/myapp
    depends_on:
      - db

  db:
    image: postgres:15
    environment:
      POSTGRES_DB: myapp
      POSTGRES_PASSWORD: secret
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data:

Terminal

$docker compose up -d

Creating network... Creating myapp_db_1... Creating myapp_web_1...

$docker compose logs -f web

(view logs)

$docker compose down

(stop everything)

Essential Commands

Terminal

$# List images

$docker images

REPOSITORY TAG IMAGE ID SIZE nginx latest a1b2c3d4e5f6 142MB node 20 b2c3d4e5f6g7 1.1GB

$# List all containers

$docker ps -a

$# View container logs

$docker logs container_id

$# Shell into running container

$docker exec -it container_id /bin/sh

$# Clean up unused images

$docker system prune -a

When to Use Docker

Good for:

Consistent development environments
Deploying applications
Running databases locally
CI/CD pipelines
Microservices

Overkill for:

Simple scripts
Learning Linux basics first
When native install is simpler

Learn Docker Properly

This is just a preview. Docker deserves its own course. Once you're comfortable with Linux basics, dive deeper into containers.

Knowledge Check

What's the difference between a Docker image and container?

Quick Reference

Command	Purpose
`docker run -d -p 80:80 img`	Run container
`docker ps`	List running containers
`docker stop id`	Stop container
`docker rm id`	Remove container
`docker images`	List images
`docker build -t name .`	Build image
`docker compose up -d`	Start compose services
`docker compose down`	Stop compose services
`docker logs id`	View logs
`docker exec -it id sh`	Shell into container

Key Takeaways

Images are templates, containers are running instances
-d for background, -p for port mapping
Dockerfile defines how to build an image
Docker Compose manages multi-container apps
Containers solve "works on my machine" problems
Learn Linux basics before diving deep into Docker

Next: security fundamentals.