How to clear Ubuntu notifications?
Kill the notify-osd program. That'll stop it from notifying until you reboot.
The package responsible for displaying the notifications is notify-osd . You can remove it by opening up a terminal and running the following command:
sudo apt-get remove notify-osd
Fair warning: this will permanently disable all notifications.
If you later decide you want the notifications back, you can run the following command:
sudo apt-get install notify-osd