Boot Repair is a graphical tool that can repair GRUB2 with a single click. This is the ideal solution to boot problems for most users.

If you have the media you instaled Ubuntu from, insert it into your computer and restart. If you don’t, download a Ubuntu live CD and burn it to a disc or install it on a USB flash drive. You can also download a dedicated Boot Repair live CD.

After booting into the live Ubuntu environment, open a terminal from the Dash and run the following commands to install Boot Repair:

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair
boot-repair

The Boot Repair window will appear after you run the boot-repair command. After it scans your system, click the Recommended repair button to repair GRUB2 with a single click.

You can also click the Advanced options header to customize GRUB2’s options without learning its command-line syntax.

Restart your computer after using the Boot Repair tool. Ubuntu should boot up normally.