Docker Operations Skill

This skill provides guidance for managing Docker containers for the To-Do List WebApp project.

Quick Commands

bash

# Start all services
npm run dev
# or
docker-compose up

# Start in background
docker-compose up -d

# Stop all services
npm run stop
# or
docker-compose down

# Restart services
npm run restart

# View status
npm run status
# or
docker-compose ps

Container Management

View Running Containers

bash

# All running containers
docker ps

# All containers (including stopped)
docker ps -a

# Specific to this project
docker ps | grep todolist

Start/Stop Individual Services

bash

# Start specific service
docker-compose start mongodb
docker-compose start backend
docker-compose start frontend

# Stop specific service
docker-compose stop mongodb
docker-compose stop backend
docker-compose stop frontend

# Restart specific service
docker-compose restart backend

Remove Containers

bash

# Stop and remove all containers
docker-compose down

# Remove containers and volumes (deletes data!)
docker-compose down -v

# Remove specific container
docker rm <container-id>

# Force remove running container
docker rm -f <container-id>

Logs and Debugging

View Logs

bash

# All services
npm run logs
# or
docker-compose logs

# Follow logs (real-time)
npm run logs
# or
docker-compose logs -f

# Specific service
npm run logs:backend
npm run logs:frontend
docker-compose logs mongodb

# Last N lines
docker-compose logs --tail=100 backend

# With timestamps
docker-compose logs -t backend

Execute Commands in Container

bash

# Open shell in backend container
docker exec -it todolist-webapp-backend-1 sh

# Open shell in MongoDB container
docker exec -it todolist-webapp-mongodb-1 sh

# Run single command
docker exec todolist-webapp-backend-1 ls -la
docker exec todolist-webapp-mongodb-1 mongosh --eval "db.stats()"

Building and Rebuilding

Rebuild Containers

bash

# Rebuild all services
docker-compose up --build

# Rebuild specific service
docker-compose build backend
docker-compose up -d backend

# Force rebuild (no cache)
docker-compose build --no-cache

Pull Latest Images

bash

# Pull latest base images
docker-compose pull

Image Management

List Images

bash

# All images
docker images

# Project images
docker images | grep todolist

Remove Images

bash

# Remove specific image
docker rmi <image-id>

# Remove unused images
docker image prune

# Remove all unused images
docker image prune -a

Volume Management

List Volumes

bash

# All volumes
docker volume ls

# Project volumes
docker volume ls | grep todolist

Inspect Volume

bash

docker volume inspect todolist-webapp_mongodb-data

Remove Volumes

bash

# Remove specific volume (data will be lost!)
docker volume rm todolist-webapp_mongodb-data

# Remove all unused volumes
docker volume prune

Network Management

List Networks

bash

docker network ls

Inspect Network

bash

docker network inspect todolist-webapp_default

Test Network Connectivity

bash

# From backend to MongoDB
docker exec todolist-webapp-backend-1 ping mongodb

# Check MongoDB connection
docker exec todolist-webapp-backend-1 nc -zv mongodb 27017

Resource Usage

View Resource Usage

bash

# All containers
docker stats

# Specific container
docker stats todolist-webapp-backend-1

# One-time snapshot
docker stats --no-stream

Disk Usage

bash

# Overall Docker disk usage
docker system df

# Detailed view
docker system df -v

Cleanup

Clean Everything

bash

# WARNING: This removes all unused Docker resources!

# Remove stopped containers
docker container prune

# Remove unused images
docker image prune

# Remove unused volumes
docker volume prune

# Remove unused networks
docker network prune

# Remove everything unused
docker system prune

# Remove everything including volumes
docker system prune --volumes

# Nuclear option (remove ALL containers, images, volumes)
docker system prune -a --volumes

Project-Specific Cleanup

bash

# Stop and remove project containers
docker-compose down

# Remove project containers and volumes
docker-compose down -v

# Clean and reinstall everything
npm run clean
npm run install:all
npm run dev

Troubleshooting

Port Already in Use

Error: "Port is already allocated"

Solutions:

bash

# Find process using port (Windows)
netstat -ano | findstr :5000
netstat -ano | findstr :5173

# Kill process by PID (Windows)
taskkill /PID <pid> /F

# Or change port in docker-compose.yml or .env

Container Keeps Restarting

Solutions:

bash

# Check logs
docker-compose logs backend

# Check container status
docker ps -a

# Inspect container
docker inspect todolist-webapp-backend-1

# Try running without detached mode
docker-compose up

Cannot Connect to MongoDB

Solutions:

bash

# Check if MongoDB is running
docker ps | grep mongo

# Check MongoDB logs
docker-compose logs mongodb

# Restart MongoDB
docker-compose restart mongodb

# Verify connection from backend
docker exec todolist-webapp-backend-1 nc -zv mongodb 27017

Out of Disk Space

Solutions:

bash

# Check disk usage
docker system df

# Clean up unused resources
docker system prune

# Remove specific large images
docker images
docker rmi <image-id>

Permission Denied

Solutions:

bash

# Run Docker commands with elevated privileges (Windows)
# Ensure Docker Desktop is running

# On Linux, add user to docker group
sudo usermod -aG docker $USER

# Restart Docker service
# Windows: Restart Docker Desktop
# Linux: sudo systemctl restart docker

Container Build Fails

Solutions:

bash

# Build with no cache
docker-compose build --no-cache

# Check Dockerfile syntax
cat backend/Dockerfile

# View build logs
docker-compose up --build

# Try building manually
cd backend
docker build -t test-backend .

Health Checks

Check Container Health

bash

# Inspect health status
docker inspect --format='{{.State.Health.Status}}' todolist-webapp-backend-1

# View health check logs
docker inspect --format='{{json .State.Health}}' todolist-webapp-backend-1

Manual Health Checks

bash

# Backend
curl http://localhost:5000/api/health

# Frontend
curl http://localhost:5173

# MongoDB
docker exec todolist-webapp-mongodb-1 mongosh --eval "db.serverStatus().ok"

Performance Optimization

Limit Resource Usage

Add to docker-compose.yml:

yaml

services:
  backend:
    deploy:
      resources:
        limits:
          cpus: '0.5'
          memory: 512M
        reservations:
          memory: 256M

Reduce Build Time

•Use .dockerignore files
•Order Dockerfile commands efficiently (dependencies first)
•Use multi-stage builds
•Leverage build cache

Best Practices

•Always use docker-compose: Don't run docker run manually
•Check logs first: When troubleshooting, always check logs
•Clean up regularly: Remove unused images and containers
•Use volumes for data: Never store data in containers
•Don't run as root: Use non-root users in production
•Tag images: Use versioning for images
•Monitor resources: Keep an eye on disk and memory usage
•Backup volumes: Regular backups of MongoDB data

Useful Aliases

Add to your shell profile (.bashrc, .zshrc, PowerShell profile):

bash

# Docker shortcuts
alias dps='docker ps'
alias dlog='docker-compose logs -f'
alias dup='docker-compose up -d'
alias ddown='docker-compose down'
alias drestart='docker-compose restart'

Docker Compose Reference

Common docker-compose Commands

bash

# Start services
docker-compose up
docker-compose up -d                    # Detached mode
docker-compose up --build               # Rebuild before starting
docker-compose up --force-recreate      # Recreate containers

# Stop services
docker-compose stop                     # Stop without removing
docker-compose down                     # Stop and remove
docker-compose down -v                  # Stop, remove, and delete volumes

# Manage services
docker-compose restart <service>
docker-compose pause <service>
docker-compose unpause <service>

# View information
docker-compose ps                       # List containers
docker-compose logs                     # View logs
docker-compose top                      # View running processes
docker-compose config                   # Validate and view config

# Execute commands
docker-compose exec <service> <command>
docker-compose run <service> <command>

Docker Operations Skill

Quick Commands

Container Management

View Running Containers

Start/Stop Individual Services

Remove Containers

Logs and Debugging

View Logs

Execute Commands in Container

Building and Rebuilding

Rebuild Containers

Pull Latest Images

Image Management

List Images

Remove Images

Volume Management

List Volumes

Inspect Volume

Remove Volumes

Network Management

List Networks

Inspect Network

Test Network Connectivity

Resource Usage

View Resource Usage

Disk Usage

Cleanup

Clean Everything

Project-Specific Cleanup

Troubleshooting

Port Already in Use

Container Keeps Restarting

Cannot Connect to MongoDB

Out of Disk Space

Permission Denied

Container Build Fails

Health Checks

Check Container Health

Manual Health Checks

Performance Optimization

Limit Resource Usage

Reduce Build Time

Best Practices

Useful Aliases

Docker Compose Reference

Common docker-compose Commands

See Also