Fonte: askubuntu
Editing the /etc/default/grub file
Type in the terminal sudo nano -B /etc/default/grub and your password if asked. The nano editor will open.
I changed the value of GRUB_DEFAULT to saved:
GRUB_DEFAULT=saved
I enabled the SAVEDEFAULT functionality by adding the following line:
GRUB_SAVEDEFAULT=true
Remember
Update-grub
Last updated: 24 Febbraio 2015 by Pierluigi Minati