手动设置Metasploit的环境变量

Question

如何手动设置 Metasploit 的环境变量，当我执行时，db_driver我收到此消息：

[*] No Active Driver
[*]        Available: 

[*]     DB Support: Enable the postgresql driver with the following command:
[*]                   * This requires libpq-dev and a build environment
[*]                 $ gem install postgres
[*]                 $ gem install pg # is an alternative that may work

经过谷歌搜索，我发现 Metasploit 设置了一些环境变量，并且可以加载已安装的驱动程序，但对我来说，Metasploit 似乎没有设置环境变量。