解決方式如下：
- Fix nm-applet can't execute error
1. 修改/etc/dbus-1/system.d/NetworkManager.conf 和 /etc/dbus-1/system.d/nm-applet.conf
將下列红色字，如果为deny，改allow<policy context=default>
<allow own="org.freedesktop.NetworkManager"/>
<allow send_destination="org.freedesktop.NetworkManager"/>
<allow send_interface="org.freedesktop.NetworkManager"/>
</policy>
2. 重新启动 dbus
sudo /etc/init.d/dbus restart
- Fix nm-applet "No connection defined" error
3. 停止 NetworkManager
sudo /etc/init.d/NetworkManager stop
4. 刪除 /etc/network/interfaces 或是更名(rename)
sudo rm /etc/network/interfaces
5. 重新启动 NetworkManager
sudo /etc/init.d/NetworkManager start
6. 执行nm-applet