I am trying to find a solution after applying the dual boot to install in my computer ubuntu. I was redirected to "How can I change/convert a Ubuntu MBR drive to a GPT, and make Ubuntu boot from EFI?" and I the community says that I have to convert the disk.

But, I would like your advice please to know which part of the disk I have to convert? because I would not like to lose my personal documents in the windows drive or do something wrong. Please is there anybody out there to give me and advice?

I put a picture of the result of gparted:

Disk partitions

warning microsoft

  • First of all please backup your systems just in case. Then from your image the partition that should be shrunk should be the Windows partion (/dev/sda3) which is 800Gb+, and what advice was given to you previously ? – George Udosen Dec 20 '16 at 21:58
  • Please follow these steps here – George Udosen Dec 20 '16 at 22:03
  • Hi George thank you for answer, they say that I have to convert Ubuntu into UEFI mode. – Lara Key Dec 20 '16 at 22:07
  • As I couldn't boot in the flash drive to install Ubuntu, I read that I have to disabled secure boot and enabled legacy, and I boot since legacy. – Lara Key Dec 20 '16 at 22:09
  • Excuse me George I can just back up Windows, I dont have a lot of information in Ubuntu, it's possible? Thank you I will follow the steps!!! – Lara Key Dec 20 '16 at 22:16


The operations discussed in this post might very well be destructive. Have a full backup of anything important before doing anything. Failure to ignore this warning is your own fault.

  1. First off, be sure you have a few hundred MB of space unallocated at the front and rear of your hard drive. As you have an EFI partition there, you're okay.
  2. In a terminal, run the command sudo gdisk /dev/sdX. Be sure to replace sdX with the proper device identifier.
  3. gdisk will prompt you that it will do the conversion. Once you're at the command window, enter w and hit enter. gdisk will give you one final warning. Confirm and move on.
  4. Your drive is now running in GPT mode. You will now need to re-install GRUB with sudo grub-install /dev/sdX (same replacement method as in step 2). You may also need to re-install the Windows bootloader using a Windows recovery disk.
  • Thank you Kaz for your answer!!! I was making the backup as you recommend, I identify the flashdrive in Ubuntu, the flash drive that I used to make the dual boot. I tried to erase the flashdrive to do the backup and accidentally I erase one file when I restart it restarts with Windows, Now I have to find how to install again ubuntu in a good way!!! – Lara Key Dec 22 '16 at 0:49
  • @LaraKey Ubuntu is likely still there. As you're now on EFI, just jump into your BIOS config and move the ubuntu entry to the top of the boot order again. – Kaz Wolfe Dec 22 '16 at 0:50
  • @LaraKey If my answer solved your problem and you're happy with the result, click the little feet checkmark by it. It will mark the answer as "accepted", make it easier to find, and give you some reputation. – Kaz Wolfe Dec 22 '16 at 17:14
  • Kaz, I just wonder if it is better to erase the partition created for Ubuntu in Windows. – Lara Key Dec 22 '16 at 17:31
  • @LaraKey Depends. What are you trying to accomplish? – Kaz Wolfe Dec 22 '16 at 17:32

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