Trivially Dockerizing a Next.js Application

Dockerfile

FROM node:18

WORKDIR /opt/app

COPY package*.json ./
RUN npm install

# use --build-arg=example_api_key=1234 to set the API_KEY env var. repeat as necessary
# in your github action or other CI/CD, set the arguments from your secrets store. 
ARG example_api_key
ARG example_public_variable
ENV API_KEY $example_api_key
ENV NEXT_PUBLIC_ENV_VARIABLE=$example_public_variable

# Copy the current directory contents into the container at /app
COPY . .

# Build the Next.js app
RUN npm run build

# Expose port 3000 for the app
EXPOSE 3000

# Start the app
CMD ["npm", "run", "start"]