获取错误：尝试获取create database时，用户“postgres”的对等身份验证失败

Question

我正在尝试为ror中的新项目创建数据库。

我实现了这个命令rake db:create，它向我显示以下错误。

Couldn't create database for {"adapter"=>"postgresql", "username"=>"postgres", "pool"=>5, "timeout"=>5000, "database"=>"demo_development"}
FATAL:  Peer authentication failed for user "postgres"

Couldn't create database for {"adapter"=>"postgresql", "username"=>"postgres", "pool"=>5, "timeout"=>5000, "database"=>"demo_test"}

请帮助我摆脱它。