Missing System Settings after removing some packages
Solution 1:
You may have accidentally removed some packages (or some dependencies which caused the package to uninstall). In any case, you may try installing (or re installing) the package ubuntu-desktop. Correct any accidental package uninstallation by:
sudo apt-get install ubuntu-desktop
Solution 2:
Uninstall and then reinstall System Settings (unity-control-center) from the Ubuntu Software Center application.
Or run this command in terminal
sudo apt-get remove unity-control-centersudo apt-get install unity-control-center