DBはPostgreSQLで、他に余分なgemを入れなければこんな感じ FROM ruby:2.5.0-alpine COPY Gemfile* /myapp/ WORKDIR /myapp RUN apk upgrade --no-cache && \ apk add --update --no-cache \ postgresql-client \ nodejs \ tzdata && \ apk add --update --no-cache --virtual=build-dependencies \ build-base \ curl-dev \ linux-headers \ libxml2-dev \ libxslt-dev \ postgresql-dev \ ruby-dev \ yaml-dev \ zlib-dev && \ gem install bundler &