安装rvm

# 安装gnupg2
$ sudo apt install gnupg2
# 安装rvm
$ gpg2 --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
$ \curl -sSL https://get.rvm.io | bash -s stable
$ source ~/.bashrc

# 替换ruby-china源
$ echo "ruby_url=https://cache.ruby-china.com/pub/ruby" > ~/.rvm/user/db
# 替换gem源
$ gem sources -l
$ gem sources --add https://gems.ruby-china.org/ --remove https://rubygems.org/
# 更新缓存
$ gem sources -u