Dockerfile for joaofnds/rails-alpine

Dockerfile

FROM ruby:alpine

# Minimal requirements to run a Rails app
RUN apk add --no-cache --update build-base \
                                linux-headers \
                                git \
                                postgresql-dev \
                                tzdata \
                                nodejs

You don't need nodejs if you're using rails for API only
You don't need postgresql-dev if you're not using Postgres as your DB