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I had Ubuntu installed on my laptop. I installed Windows 7 and now I can't access Ubuntu. But the partition is there. I thought I would get a choice of operating systems at the start but I don't. I want them both. How do I get a choice of operating systems during system start up?

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3 Answers 3

up vote 6 down vote accepted

Steps:

  • Boot from a Ubuntu LiveCD.
  • Select Try Ubuntu.
  • Open a terminal (Ctrl + Alt + T).
  • Execute the following commands:

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

  • Follow the instructions.
  • Reboot.

This will re-install GRUB, which was removed by the Windows installer. You'll be able to boot into both operating systems now.

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  1. Boot from the live CD.
  2. Determine the partition number of your main partition. GParted can help you here. I'm going to assume in this answer that it's /dev/sda2, but make sure you use the correct partition number for your system!
  3. Mount your partition:

    sudo mount /dev/sda2 /mnt  # make sure that sda2 is correct!
    
  4. Bind mount some other necessary stuff:

    for i in /sys /proc /run /dev; do sudo mount --bind "$i" "/mnt$i"; done
    
  5. chroot into your Ubuntu install:

    sudo chroot /mnt
    
  6. At this point, you're in your install, not the live CD, and running as root. Update grub:

    update-grub
    

    If you get errors, go to step 7. (Otherwise, it is optional.)

  7. Depending on your situation, you might have to reinstall grub:

    grub-install /dev/sda
    update-grub
    
  8. If everything worked without errors, then you're all set:

    exit
    sudo reboot
    
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You installed Ubuntu and with it a bootloader called GRUB2.

Now you have installed Wnindows with its own bootloader and it overwrites GRUB2.

The easiest way - for the beginning - is to install ubuntu again with the bootloader. That will not overwrite the Windows Loader, but it integrated the Windows Loader in the GRUB2-Menu and you can choose the System you want to boot at startup. This is called Dualboot.

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While 'reinstalling ubuntu will get you ubuntu back, but surely that's not the first thing someone wants? –  Nanne Mar 5 '13 at 15:28
    
@Nanne I agree. 1. It will remove ALL data from Windows 7 (Because you are overwriting Win7) and 2. All data will be lost from Ubuntu, too. So that won't help at all! –  nerof61 Mar 5 '13 at 15:50
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