hello-world Run

# ===== Run hello-world =====
docker run --rm hello-world
# Pulls the image, starts a one-shot container, prints, then exits.
# --rm removes the container after exit.

# ===== Run a server =====
docker run -d --name web -p 8080:80 nginx:1.27-alpine
# -d: detached (background)
# --name: stable name (default is random)
# -p HOST:CONTAINER: port mapping

# Visit http://localhost:8080

# ===== Inspect =====
docker ps                    # running containers
docker ps -a                 # all (incl stopped)
docker logs web              # stdout/stderr of the container
docker logs -f web           # follow
docker exec -it web sh       # exec a shell inside

# ===== Stop + remove =====
docker stop web              # graceful (SIGTERM, then SIGKILL)
docker rm web                # remove the stopped container
# Or: docker rm -f web (force stop + remove)

# ===== Volumes (persistence) =====
docker volume create pg-data
docker run -d --name pg \
  -e POSTGRES_PASSWORD=dev \
  -v pg-data:/var/lib/postgresql/data \
  -p 5432:5432 \
  postgres:16

# Bind mount your code:
docker run -d --name dev \
  -v "$PWD":/app -w /app \
  -p 3000:3000 \
  node:20-alpine npm run dev

# ===== Environment variables =====
docker run --rm -e NODE_ENV=production -e PORT=3000 my-app

# Or from a file:
docker run --rm --env-file ./.env my-app

# ===== Networks =====
docker network create app-net
docker run -d --name pg --network app-net postgres:16
docker run -d --name api --network app-net -p 3000:3000 my-api
# 'api' can reach 'pg' at hostname 'pg'.

# ===== Cleaning up =====
docker stop $(docker ps -q)        # stop all running
docker rm $(docker ps -aq)         # remove all containers
docker image prune                  # untagged + dangling images
docker system prune -a              # everything not in use

# ===== Common gotchas =====
# - Port already in use: change HOST port (use -p 8081:80)
# - Cannot connect from host: forgot -p mapping or wrong CONTAINER port
# - State lost after rm: use volumes for any persistence
# - Permission errors with bind mounts: rootless containers + volume ownership

# ===== Patterns to internalise =====
# - --rm for one-shots; --name + -d for daemons
# - Volumes for data you must keep; bind mounts for code in dev
# - Networks for inter-container DNS; do not rely on IPs
# - Always check 'docker logs' first when something fails

# ===== Pitfalls =====
# - Forgetting -p -> service is unreachable from host
# - Not mounting a volume -> data wiped on next run
# - Running as root inside containers in production
# - Leaving 'latest' tags everywhere in prod

docker run hello-world
# Pulls the image, runs the container, prints a welcome message.