How to fix Grub2 error 15 in Ubuntu

Error 15 "file not found" in Grub2 mostly occurs when you have installed grub2 to /boot but the grub legacy is still installed in MBR (Master boot record). This mostly happens when you are upgrading and while installing grub2 you didn't select the drive when running "update-from-grub-legacy". This howto gives you a fix for this problem.

Follow the steps given below step by step:

1) Boot from Live CD in to a Live session and run this command in the terminal (Applications-> Accessories-> Terminal).

[shredder12]$ sudo fdisk -l

2) The above command will give you a list of partitions. You will have to recognize the concerned linux partition and mount it in /mnt using the following command. I am assuming /dev/sda1 as the concerned partition.

[shredder12]$ sudo mount /dev/sda1 /mnt

3) If you have a separate /boot partition then you will have to mount it too. I will assume that /dev/sda2 is the /boot partition and you can mount it using this command. Please be careful while doing this, make sure that the partitions are recognized and mounted correctly.

[shredder12]$ sudo mount /dev/sda2 /mnt/boot

4) Now, mount the rest of the devices.

[shredder12]$ sudo mount --bind /dev /mnt/dev

5) Now, we will be running commands to reconfigure grub2 as root of the linux installed partition. So, we will chroot command to change the linux root directory to /mnt. In this way , we will be get a root prompt to execute the commands as the root user of the linux installed partition.

[shredder12]$ sudo chroot /mnt

Since, we get a root prompt so now on we won't need sudo to execute commands with root priviliges.

6) Tell grub which drive it should install itself to. Use spacebar to select and don't continue without selecting one.

[root]$ dpkg-reconfigure grub-pc

7) Either press Ctrl-D to exit the chroot or type exit.

8) Unmount the partitions we mounted.

[shredder12]$ sudo umount /mnt/dev

9) Unmount /mnt

[shredder12]$ sudo umount /mnt

Now, when you will restart your system you will be able to boot using Grub2 directly into the linux installed partition.