ubuntu重启networkmanager的指令

sudo service network-manager stop
sudo rm /var/lib/NetworkManager/NetworkManager.state
sudo service network-manager start

有可能解决网络图标消失的情况，如果没解决的话，可以尝试在以上代码之后加上
sudo vim /etc/NetworkManager/nm-system-settings.conf
false-- 改成–true
sudo service network-manager restart