How to Repair, Restore, or Reinstall Grub 2 with a Ubuntu Live CD or USB


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Grub 2 typically gets overridden when you install Windows or another Operating System. To make Ubuntu control the boot process, you need Reinstall (Repair/Restore) Grub using a Ubuntu Live CD.

Warning:

Using the sudo command, especially from a Live CD can do serious damage to your system. Read all instructions and confirm you understand before executing any commands. When pasting into the Terminal, use Ctrl+Shift+V, NOT Ctrl+V.

Terminal Commands:

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/sda5 /mnt.


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  1. sudo mount /dev/sdXY /mnt
  2. Now bind the directories that grub needs access to to detect other operating systems, like so:
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  5. Now we jump into that using chroot.
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  8. Now install, check, and update grub.
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  10. This time you only need to add the partition letter (usually a) to replace X, for example: grub-install /dev/sda, grub-install –recheck /dev/sda.
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  12. grub-install /dev/sdX
  13. grub-install --recheck /dev/sdX
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  15. Now grub is back, all that is left is to exit the chrooted system and unmount everything.
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  18. Shut down and turn your computer back on, and you will be met with the default Grub2 screen.
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  20. You may want to update grub or re-install burg however you like it.
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  22. Congratulations, you have just Repaired/Restored/Reinstalled Grub 2 with a Ubuntu Live CD!

URL: http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd#.UXu_FCuUXw0

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