The following is a systray applet icon that appeared in my Unity session after I upgraded to Ubuntu 16.10. Its menu is tall, narrow and empty. What is it?
The "forbidden" icon indicates that one of the panel indicator's (for example, Klipper) can't be loaded or is no longer functioning, possibly because it has been discontinued in Ubuntu 16.10.
If it hasn't been discontinued in Ubuntu 16.10, showing your system's process list by running
ps -ef | grep indicator- will provide more information about which process is causing it. This will show the panel indicators that have the string
indicator- in their names as the panel indicators from the default Ubuntu repositories do. To show all of the process list run
In my case it was Klipper (clipboard manager from Plasma).
You can try to kill them:
# killall klipper
I disabled startup of this applet removing it in "Startup Application Preferences" and unknown icon disappeared.
If this is a laptop, it seems the indicator you are missing would be indicator-power. I have the same problem on a Lenovo Thinkpad yoga 370. So far that only seems to show when the battery is 100% charged and connected to AC. Don't know how this could be fixed tho.