Dockerfile

ELI5 — The Vibe Check

A Dockerfile is the recipe for building a Docker image. It's a text file with step-by-step instructions: start from this base OS, install these tools, copy in my code, run this command to start. Docker reads the recipe and bakes your image. Change the recipe, get a different image.

Real Talk

A Dockerfile is a text file containing sequential instructions for building a container image. Each instruction creates a new immutable layer. Common instructions include FROM (base image), RUN (execute commands), COPY (add files), ENV (set env vars), and CMD/ENTRYPOINT (define startup command).

Show Me The Code

FROM node:20-alpine

WORKDIR /app

COPY package*.json ./
RUN npm ci

COPY . .
RUN npm run build

EXPOSE 3000
CMD ["node", "dist/index.js"]

When You'll Hear This

"Write a Dockerfile so the app can run in any cloud environment." / "The Dockerfile is missing a COPY step — that's why the build is failing."