多种方法多多尝试
1.使用nmcli,该命令可以完成网卡上所有的配置工作,并且可以写入配置文件,永久生效
sudo nmcli networking off
sudo nmcli networking on
2.删除NetworkManager.state文件
sudo service network-manager stop
sudo rm /var/lib/NetworkManager/NetworkManager.state
sudo service network-manager start
3.修改NetworkManager.conf
sudo gedit /etc/NetworkManager/NetworkManager.conf
把false改成true
sudo service network-manager restart