Installing Ubuntu 15.10

Bootloader Failures

Occasionally, the bootloader doesn't appear after an Ubuntu installation, or you can boot only one system. Loading Windows after installing Ubuntu often leads to a bootloader failure. Refer to the "Revival" box for commands you will want to enter in a terminal window. These commands install the GRUB 2 bootloader with help from a Live system so that GRUB correctly identifies all systems.

Revival

To revive an installed Ubuntu, boot up Live mode on the DVD in this issue by choosing the Try Ubuntu without installing option. Be sure that the Live and installed versions are the same architecture. Then, invoke a terminal and execute the following commands. Substitute for /dev/sda6 entry the specific partition in which the root directory (/ ) of the installed Ubuntu is located.

$ sudo mount /dev/sda6 /mnt
$ sudo mount -o bind /dev /mnt/dev
$ sudo mount -o bind /sys /mnt/sys
$ sudo mount -t proc /proc /mnt/proc
$ sudo chroot /mnt
$ grub-mkconfig -o /boot/grub/grub.cfg
$ update-grub2
$ grub-install /dev/sda
$ exit
$ sudo reboot

Use the chroot command (change root) to mount the installed system into your Live system and work with it as if you had booted it. Now you can set up a new GRUB 2.

Infos