Sep 25, 2012 · As in previous Grub 2 versions, the default boot option is set by a setting of the /etc/default/grub file. The first menuentry on the main menu is designated by the entry GRUB_DEFAULT=0 Entries displayed on the main menu can be designated by number or title as with earlier versions of Grub 2. GRUB_DEFAULT="Advanced options for Ubuntu>x" (make sure to include the quotations), where x is the index of the old kernel on the sub-menu, or the name of the kernel as it appears in /boot/grub/grub.cfg. For example, GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 5.4.0-45-generic" Then build the updated grub menu: sudo update-grub Dec 28, 2016 · Ubuntu is installed on a hdd, w10 installed on a ssd. I BELIEVE that they are both efi installs (cannot remember which way I did it) because both disks are GPT format. On the other hand, if I select UEFI only for boot options in my bios, only "ubuntu" boot device is available on the F12 screen. First use your Ubuntu LiveCD or USB, etc to boot into a Ubuntu Live desktop. Then install Boot-repair using the method described in the post. Then open boot-repair and from its main window under the "Main options" tab make sure the following settins are activated/selected. *. Reinstall GRUB *. Unhide boot menu *. Repair file systems