MongoDB应用

1. Ubuntu安装MongDB后启动报错
   使用的是windows sub system的Ubuntu，用sudo apt install mongodb安装mongDB,这样安装的不是官方最新版本，但是简单。然后查看状态sudo apt install mongodb报错：

System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down

可以尝试用sudo /etc/init.d/mongodb status

• Checking status of database mongodb [fail]

这样表示未启动。用sudo /etc/init.d/mongodb start启动就好了。