Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Sometimes the dock and top bar do not appear. What to do?
I usually just Ctrl+Alt+F2 login to command line and reboot. It then goes away.
I was also having this problem intermittently, but it was due to a different bug and this fix solved it for me:
sudo mv /etc/xdg/autostart/at-spi-dbus-bus.desktop /etc/xdg/autostart/at-spi-dbus-bus.disabled
If you have an Intel Graphics card that's a known bug and it should be solved by now. Try updating your system (open AppCentre, go to Updates and press Update All).
Still happening randomly at boot.
A solution faster than rebooting is to switch to another console and restart lightdm with sudo service lightdm restart
sudo service lightdm restart
Do you have a logitech wireless mouse or keyboard?
If so, Try unplugging the receiver and see if the wingpanel comes back