Writing Dockerfiles

A Dockerfile is a text document that contains all the commands to assemble an image.

Basic Dockerfile

dockerfile

FROM node:18-alpine

WORKDIR /app

COPY package*.json ./

RUN npm install

COPY . .

EXPOSE 3000

CMD ["npm", "start"]

Common Instructions

dockerfile

# Base image
FROM python:3.11

# Set working directory
WORKDIR /app

# Copy files
COPY requirements.txt .
COPY . /app

# Run commands
RUN pip install -r requirements.txt

# Environment variables
ENV NODE_ENV=production

# Expose ports
EXPOSE 8000

# Default command
CMD ["python", "app.py"]

Building an Image

bash

docker build -t my-app .
docker build -t my-app:v1.0 .

Multi-stage Builds

dockerfile

# Build stage
FROM node:18 AS builder
WORKDIR /app
COPY . .
RUN npm ci && npm run build

# Production stage
FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html