Example Docker setup for a Rails app

docker-compose.yml

app:
  build: .
  links:
    - db:db
    - redis:redis
    - memcache:memcache
  volumes:
    - ./:/app
  environment:
    PGHOST: db
    PGUSER: postgres
    REDIS_URL: redis://redis
    MEMCACHE_SERVERS: memcache
    BUILDKITE_PARALLEL_JOB:
    BUILDKITE_PARALLEL_JOB_COUNT:
    BUILDBOX_JOB_ID:
    CI:
db:
  image: postgres
redis:
  image: redis
memcache:
  image: tutum/memcached

Dockerfile

FROM ruby:2.2.0

# Add official postgresql apt deb source
RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys B97B0AFCAA1A47F044F244A07FCC7D46ACCC4CF8
RUN echo "deb http://apt.postgresql.org/pub/repos/apt/ precise-pgdg main" > /etc/apt/sources.list.d/pgdg.list

# Update all the things
RUN apt-get update

# Generate UTF-8 locale
RUN apt-get install -y locales
RUN dpkg-reconfigure locales && \
  locale-gen C.UTF-8 && \
  /usr/sbin/update-locale LANG=C.UTF-8
RUN echo 'en_US.UTF-8 UTF-8' >> /etc/locale.gen && locale-gen

# Set UTF-8
ENV LC_ALL C.UTF-8
ENV LANG en_US.UTF-8
ENV LANGUAGE en_US.UTF-8

# Install the postgres client
RUN apt-get install -y postgresql-client

# Install node.js (javascript runtime for Ruby)
RUN apt-get install -y curl && \
     curl -sL https://deb.nodesource.com/setup | bash - && \
     apt-get install -y nodejs

RUN mkdir /app
WORKDIR /app