オプションのデフォルトを設定するには、~/.gemrc か /etc/gemrc を作成する $ gem help environment (省略) Command line argument defaults and some RubyGems defaults can be set in ~/.gemrc file for individual users and a /etc/gemrc for all users. A gemrc is a YAML file with the following YAML keys: :sources: A YAML array of remote gem repositories to install gems from :verbose: Verbosity of the gem command. false, true, and :real