Grub is the default boot loader for Ubuntu and it comes with a huge set of options that you might be inclined to tweek when ever you choose to debug a problem during bootup. The simple quickfire way to make Grub do what you want is to edit it just before the boot process occurs (Hit ‘E’ key when the options are listed), this provides for easy access but the changes are non permanent. The next time you reboot the options will have switched to the default.
To make permanent changes to Grub you need to edit the “/etc/default/grub” file and rebuild your Grub.