centos8/redhat8 无法上网，通过启动systemctl start NetworkManger搞定

在systemd里面，可以直接使用systemctl进行管理

启动：systemctl start NetworkManger

关闭：systemctl stop NetworkManager

开机启动：systemctl enable NetworkManger

查看是否开机启动：systemctl is-enabled NetworkManager

禁用开机启动：systemctl disable NetworkManager

启动：service NetworkManager start

关闭：service NetworkManager stop

开机启动：chkconfig NetworkManager on

禁用开机启动：chkconfig NetworkManager off