我需要使用docker-compose创建Rails和Mysql容器。当我尝试使用创建容器之间的链接时docker-compose up，我得到

无法启动容器9b271c58cf6aecaf017dadaf5b无法链接到未运行的容器：/ puma_db_1 AS / puma_web_1 / db

档案

Docker文件

FROM ubuntu:14.04

RUN apt-get -y update
RUN apt-get -y install git curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

RUN apt-get -y install libmysqlclient-dev
RUN git clone https://github.com/sstephenson/rbenv.git /root/.rbenv
RUN git clone https://github.com/sstephenson/ruby-build.git /root/.rbenv/plugins/ruby-build
RUN echo 'eval "$(rbenv init -)"' >> $HOME/.profile
RUN echo 'eval "$(rbenv init -)"' >> $HOME/.bashrc

RUN rbenv install 2.1.5
RUN rbenv global 2.1.5
RUN gem install rails -v 4.0.11

ADD app.tar.gz /home/
WORKDIR /home/app

RUN bundle install
EXPOSE 3000
CMD ["rails", "server", "-b", "0.0.0.0"]

docker-compose.yml

db:  
  image: mysql:latest
  environment:
    MYSQL_DATABASE: app_development
    MYSQL_USER: mysql
    DATABASE_PASSWORD: onetwo
    ROOT_PASSWORD: onetwo
web:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  ports:
    - "4000:3000"
  links:
    - db