Ubuntu 遇到Failed to stop network-manager.service: Unit network-manager.service not loaded或者网络丢失情况

Ubuntu遇到网络丢失，连不上网络/网络图标消失/获取不了镜像源
Failed to stop network-manager.service: Unit network-manager.service not loaded.
搜了很多，都是network-manager的命令，ubuntu会提示没有这个服务，原因是服务名称错误，解决方案如下

执行以下语句：

 sudo service NetworkManager stop sudo rm /var/lib/NetworkManager/NetworkManager.state sudo service NetworkManager start