Перезагрузиться в выбранную систему

Reboot in selected os

Edit /etc/default/grub: sudo gedit /etc/default/grub and modify the "GRUB_DEFAULT=0" value (it should be on line 4) from "0" to "saved" (without the quotes) so that it looks like this:

sudo update-grub

Now to reboot Ubuntu in Windows or some other OS, run the following command: sudo grub-reboot X