The Dockerfile instructions that matter — FROM, WORKDIR, COPY, RUN, EXPOSE, CMD

You are writing a Dockerfile and want the essential instructions in the order they are usually layered.

FROM node:22-alpine        # base image — always pin a version
WORKDIR /app               # following paths are relative to /app
COPY package*.json ./      # manifests first (better layer caching)
RUN npm ci --omit=dev      # install deps at build time
COPY . .                   # then the source
EXPOSE 3000                # documents the port (does NOT publish it)
CMD ["node", "server.js"]  # default command; ENTRYPOINT + CMD = fixed binary + default args

Good to know

Copy the dependency manifests before the source — that ordering is what makes layer caching work for you. EXPOSE documents the port; it does not publish it.

Docker Cheatsheet one-page card — commands that actually work — The full one-page card — Docker Cheatsheet. Get the complete cheatsheet on GitHub