執行mongo,報錯如下：
./mongo
MongoDB shell version v4.0.0
connecting to: mongodb://127.0.0.1:27017
2018-07-30T14:24:00.807+0800 E QUERY [js] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused :
connect@src/mongo/shell/mongo.js:251:13
@(connect):1:6
exception: connect failed
是沒有執行mongod,就直接執行mongo，纔會報錯
操作：
sudo ./mongod -dbpath /data/db/
./mongo
#都在mongodb的bin目錄下
不知道/data/db是啥：https://blog.csdn.net/qq_39729527/article/details/81285072