docker

Docker Skill

Manage Docker containers and Compose stacks: build, run, stop, logs, exec, prune, multi-service orchestration.

Use When

• Building/running containers or debugging container issues
• Setting up docker-compose stacks
• Managing images, volumes, networks
• Containerizing applications
• Multi-service orchestration

Quick Reference

Container Lifecycle

# Run container (detached, with name, port mapping, env vars)
docker run -d --name myapp -p 8080:80 -e NODE_ENV=production --restart unless-stopped myimage:latest

# Interactive shell
docker exec -it myapp bash

# Logs (follow, with timestamps, last 100 lines)
docker logs -f --tail 100 --timestamps myapp

# Stop / remove
docker stop myapp && docker rm myapp

# List running (all with -a)
docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"

Building Images

# Build with tag
docker build -t myapp:latest .

# Multi-stage build (target specific stage)
docker build --target production -t myapp:prod .

# Build with build args
docker build --build-arg VERSION=1.2.3 -t myapp:1.2.3 .

# No cache rebuild
docker build --no-cache -t myapp:latest .

Docker Compose

# Start all services (detached)
docker compose up -d

# Start specific service
docker compose up -d postgres

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

# View logs across services
docker compose logs -f --tail 50

# Stop and remove everything (including volumes)
docker compose down -v

# Scale a service
docker compose up -d --scale worker=3

# Execute command in running service
docker compose exec web bash

# View service status
docker compose ps

Debugging

# Inspect container (full JSON)
docker inspect myapp

# Resource usage
docker stats --no-stream

# See container processes
docker top myapp

# Copy files out of container
docker cp myapp:/app/logs/error.log ./error.log

# Check why container exited
docker inspect --format='{{.State.ExitCode}} {{.State.Error}}' myapp

# Network debugging
docker network ls
docker network inspect bridge

# Enter stopped container's filesystem
docker run --rm -it --entrypoint sh myimage:latest