Peek inside a Docker image

A ‘dockerfile’ contains all the instructions to build a Docker image. Here’s my first draft for a project I’m working on:

FROM node:20
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["node", "server.js"]

COPY . . is copying all of the files in my project into the working directory of the image so they can be run. Of course we don’t need them all for the app - for example the node_modules directory will be created when we npm install so no need to copy that, and I don’t need all my dot files in the container.