Using the sudo command, especially from a Live CD can do serious damage to your system. When pasting into the Terminal, use Ctrl+Shift+V, NOT Ctrl+V.
Mount the partition your Ubuntu Installation is on. If you are not sure which it is, launch GParted (included in the Live CD) and find out. It is usually a EXT4 Partition. Replace the XY with the drive letter, and partition number, for example: sudo mount /dev/sda1 /mnt.
sudo mount /dev/sdXY /mnt
Now bind the directories that grub needs access to to detect other operating systems, like so.
sudo mount --bind /dev /mnt/dev
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
Now we jump into that using chroot.
sudo chroot /mnt
Now install, check, and update grub.
This time you only need to add the drive letter (usually a) to replace X, for example: grub-install /dev/sda, grub-install –recheck /dev/sda.
grub-install --recheck /dev/sdX
Now grub is back, all that is left is to exit the chrooted system and unmount everything.
sudo umount /mnt/sys
sudo umount /mnt/proc
sudo umount /mnt/dev/pts
sudo umount /mnt/dev
sudo umount /mnt
Shut down and turn your computer back on, and you will be met with the default Grub2 screen.
If the above not yet fixed try to add the below parameter to grub.
Start your system and wait for the GRUB menu to show, if you don't see a GRUB menu, press and hold the left Shift key right after starting the system
Now highlight the kernel you want to use, and press the e key. You should be able to see and edit the commands associated with the highlighted kernel.
Go down to the line starting with linux and add your parameter foo=bar to its end.
Now press Ctrl + x to boot.
To make this change permanent:
From a terminal (or after pressing Alt + F2) run:
sudo vim /etc/default/grub
and enter your password.
Add the below line
Save the file and close the editor.
to update GRUB's configuration file (you probably need to enter your password).
On the next reboot the kernel should be started with the boot parameter.