Panel icons disappear at startup

It happens to me to from time to time. I don't know the cause.

To make the missing panel indicators reappear without rebooting you can restart the indicators manually by running the following command in a terminal or with Alt+F2

restart unity-panel-service  

The panel indicators will blink off for a second, and then all of the panel indicators will restart and immediately reappear.

In Ubuntu 15.04 and later restart the panel indicators manually by running the following command:

systemctl --user restart unity-panel-service   

In Ubuntu 17.10 and later GNOME has replaced Unity as the default desktop environment. To make the missing panel indicators reappear without rebooting in Ubuntu 17.10 and later run the following command:

setsid gnome-shell --replace # Press Enter again before closing the terminal.