在Raspberry上连接MongoDB失败

Question

如何在Raspberry上处理MongoDB连接失败？
我已经安装了MongoDB。
当我运行
> mongo

我得到

MongoDB shell version: 2.4.14
connecting to: test
Fri Jan 25 10:46:28.648 Error: couldn't connect to server 127.0.0.1:27017 at src/mongo/shell/mongo.js:145
exception: connect failed