andrea@andrea-ThinkPad-E555:~/c++$ sudo gedit /boot/grub/grub.cfg 

(gedit:12102): Gtk-WARNING **: Attempting to read the recently used resources file at '/home/andrea/.local/share/recently-used.xbel', but the parser failed: Apertura del file "/home/andrea/.local/share/recently-used.xbel" non riuscita: Permesso negato.