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I have a multiboot system with Windows XP and Ubuntu 13.04. I use Grub 2 to boot from the MBR to a chainloader in the Ubuntu partition, and the chainloader gives me the option of booting to XP or Ubuntu. I just got a new drive and cloned the entire original drive (A) to the new drive (B). Well, something happened and I don't have a backup that will help me.

The chainloader on drive A is corrupt, and drops me down to a Grub Rescue prompt. I thought maybe the drive designations were changed, so I was able to hack in to the menu and try and modify them, using fdisk to give me the drive designations, but that didn't work. I have since gone back to a generic MBR on drive A to be able to boot into XP.

On drive B, the chainloader is also corrupt, but doesn't seem to be as bad. It goes into the menu, and I can select my XP partition and it boots fine, but I'm not able to boot into Ubuntu.

Right now, I'm running off the Ubuntu 13.04 live DVD. I am unable to mount the Ubuntu partition for drive A. Perhaps I need to let that go. I can clone back to it later. I can mount the Ubuntu partition for drive B, and get in and modify files and do all kinds of stuff. I figure I just need to rebuild my chainloader grub.cfg file and everything will be OK, but when I run the command "sudo update-grub", I get the error message failed to get canonical path of /cow. I did some poking around, and came across the suggestion to run the command sudo chroot /mnt. I do that and get the error message cannot find a device for / (is /dev mounted?). I try changing to the mount of my drive B (/mnt/sdb5) and it says No such file or directory.

I guess I have two questions:

  1. Am I thinking correctly that if I can run update-grub and rebuild my grub.cfg file on drive B, I will be able to boot into Ubuntu?
  2. If so, how can I rebuild it when I'm running off the live DVD?
share|improve this question
    
as you said, if you have a live cd you might want to repair the grub using askubuntu.com/q/337244/169736 –  Braiam Nov 17 '13 at 19:26
    
thanks. I'll check it out –  randyman99 Nov 17 '13 at 19:28
    
I running into a problem when I try to set prefix. "unexpected error near token (". DOn't know why, unable to get around it or find a solution. I'm going to have to try something else. TJTS. –  randyman99 Nov 17 '13 at 19:58
    
Tried a grub repair disk. It hung up and now when I boot it says missing operating system. I was trying to find a quicker solution than reinstalling Ubuntu from scratch, but this seems to be taking me in the opposite direction. Now I'm back on XP on drive A. At least I have 1 working operating system out of 4. –  randyman99 Nov 17 '13 at 20:49

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