Docker Essentials

Docker Essentials

Essential Docker commands for container and image management.

Container Lifecycle

Running containers

Run container from image
docker run nginx

Run in background (detached)
docker run -d nginx

Run with name
docker run --name my-nginx -d nginx

Run with port mapping
docker run -p 8080:80 -d nginx

Run with environment variables
docker run -e MY_VAR=value -d app

Run with volume mount
docker run -v /host/path:/container/path -d app

Run with auto-remove on exit
docker run --rm alpine echo "Hello"

Interactive terminal
docker run -it ubuntu bash

Managing containers

List running containers
docker ps

List all containers (including stopped)
docker ps -a

Stop container
docker stop container_name

Start stopped container
docker start container_name

Restart container
docker restart container_name

Remove container
docker rm container_name

Force remove running container
docker rm -f container_name

Remove all stopped containers
docker container prune

Container Inspection & Debugging

Viewing logs

Show logs
docker logs container_name

Follow logs (like tail -f)
docker logs -f container_name

Last 100 lines
docker logs --tail 100 container_name

Logs with timestamps
docker logs -t container_name

Executing commands

Execute command in running container
docker exec container_name ls -la

Interactive shell
docker exec -it container_name bash

Execute as specific user
docker exec -u root -it container_name bash

Execute with environment variable
docker exec -e VAR=value container_name env

Inspection

Inspect container details
docker inspect container_name

Get specific field (JSON path)
docker inspect -f '{{.NetworkSettings.IPAddress}}' container_name

View container stats
docker stats

View specific container stats
docker stats container_name

View processes in container
docker top container_name

Image Management

Building images

Build from Dockerfile
docker build -t myapp:1.0 .

Build with custom Dockerfile
docker build -f Dockerfile.dev -t myapp:dev .

Build with build args
docker build --build-arg VERSION=1.0 -t myapp .

Build without cache
docker build --no-cache -t myapp .

Managing images

List images
docker images

Pull image from registry
docker pull nginx:latest

Tag image
docker tag myapp:1.0 myapp:latest

Push to registry
docker push myrepo/myapp:1.0

Remove image
docker rmi image_name

Remove unused images
docker image prune

Remove all unused images
docker image prune -a

Docker Compose

Basic operations

Start services
docker-compose up

Start in background
docker-compose up -d

Stop services
docker-compose down

Stop and remove volumes
docker-compose down -v

View logs
docker-compose logs

Follow logs for specific service
docker-compose logs -f web

Scale service
docker-compose up -d --scale web=3

Service management

List services
docker-compose ps

Execute command in service
docker-compose exec web bash

Restart service
docker-compose restart web

Rebuild service
docker-compose build web

Rebuild and restart
docker-compose up -d --build

Networking

List networks
docker network ls

Create network
docker network create mynetwork

Connect container to network
docker network connect mynetwork container_name

Disconnect from network
docker network disconnect mynetwork container_name

Inspect network
docker network inspect mynetwork

Remove network
docker network rm mynetwork

Volumes

List volumes
docker volume ls

Create volume
docker volume create myvolume

Inspect volume
docker volume inspect myvolume

Remove volume
docker volume rm myvolume

Remove unused volumes
docker volume prune

Run with volume
docker run -v myvolume:/data -d app

System Management

View disk usage
docker system df

Clean up everything unused
docker system prune

Clean up including unused images
docker system prune -a

Clean up including volumes
docker system prune --volumes

Show Docker info
docker info

Show Docker version
docker version

Common Workflows

Development container:

docker run -it --rm \
  -v $(pwd):/app \
  -w /app \
  -p 3000:3000 \
  node:18 \
  npm run dev

Database container:

docker run -d \
  --name postgres \
  -e POSTGRES_PASSWORD=secret \
  -e POSTGRES_DB=mydb \
  -v postgres-data:/var/lib/postgresql/data \
  -p 5432:5432 \
  postgres:15

Quick debugging:

Shell into running container
docker exec -it container_name sh

Copy file from container
docker cp container_name:/path/to/file ./local/path

Copy file to container
docker cp ./local/file container_name:/path/in/container

Multi-stage build:

Dockerfile
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

Useful Flags

docker run flags:

• --d: Detached mode (background)
• --it: Interactive terminal
• --p: Port mapping (host:container)
• --v: Volume mount
• --e: Environment variable
• ---name: Container name
• ---rm: Auto-remove on exit
• ---network: Connect to network

docker exec flags:

• --it: Interactive terminal
• --u: User
• --w: Working directory

Tips

• -Use .dockerignore to exclude files from build context
• -Combine RUN commands in Dockerfile to reduce layers
• -Use multi-stage builds to reduce image size
• -Always tag your images with versions
• -Use --rm for one-off containers
• -Use docker-compose for multi-container apps
• -Clean up regularly with docker system prune

Documentation

Official docs: https://docs.docker.com/

Dockerfile reference: https://docs.docker.com/engine/reference/builder/

Compose file reference: https://docs.docker.com/compose/compose-file/