Docker Essentials

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name: docker-essentials description: Essential Docker commands and workflows for container management, image operations, and debugging. homepage: https://docs.docker.com/ metadata: {"clawdbot":{"emoji":"🐳","requires":{"bins":["docker"]}}}

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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/

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