DecypherLabs Docs

A Dockerfile is a text file that defines how to build a Docker image.

Basic structure

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
EXPOSE 3000
CMD ["node", "index.js"]

Key instructions

FROM — Base image
WORKDIR — Set working directory inside the container
COPY — Copy files from host to image
RUN — Execute commands during build
EXPOSE — Document which port the app uses
CMD — Default command when container starts

Building and running

docker build -t my-app .
docker run -p 3000:3000 my-app

docker build -t my-app .
docker run -p 3000:3000 my-app

docker build -t my-app .
docker run -p 3000:3000 my-app

import React from 'react';
import ReactDOM from 'react-dom';
import ReactMarkdown from 'react-markdown';

const input = '# This is a header\n\nAnd this is a paragraph'

ReactDOM.render(
  <ReactMarkdown source={input} />,
  document.getElementById('container')
)

Use -t to tag the image. Use -p to map host port to container port.