Example of Dockerfile for a nodejs app

cinema.microservices.Dockerfile

# the first thing we specify in a Dockerfile is the base image. 
# This is essentially bare bones alpine linux with node installed.
FROM node:7.5.0-alpine

# Creates a non-root-user.
RUN addgroup -S nupp && adduser -S -g nupp nupp

# Sets the HOME environment variable.
ENV HOME=/home/nupp

# Copy the files specified, in the 'app' folder.
COPY package.json npm-shrinkwrap.json $HOME/app/

# Copy our src code, in the 'app/src' folder.
COPY src/ $HOME/app/src

# Add dumb-init to our alpine linux.
ADD https://github.com/Yelp/dumb-init/releases/download/v1.1.1/dumb-init_1.1.1_amd64 /usr/local/bin/dumb-init

WORKDIR $HOME/app

# Executes some bash commands and installs our project dependencies.
RUN chown -R nupp:nupp $HOME/* /usr/local/ && \
    chmod +x /usr/local/bin/dumb-init && \
    npm cache clean && \
    npm install --silent --progress=false --production && \
    chown -R nupp:nupp $HOME/*

# Changes the root user to a non-root-user for security.
USER nupp

# Expose our server port.
EXPOSE 3000

# the CMD command tells docker that this image should run the node executable. 
# When the executable terminates, the container shuts down.
CMD ["dumb-init", "npm", "start"]