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I have a very peculiar condition where I need GPT based disk for hackintosh. I also want to install the following distros:

* Ubuntu 16.04
* Elementary OS Luna (Ubuntu 12 based)

I'm pretty confused by now as to whether I can install the above using legacy boot on GPT partition. Is this possible?

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  • Why don't you want to just use EFI? It's more stable. Oct 8, 2016 at 13:56
  • Because I have a Dell 15R N5110. It does not support EFI or that's what my research has told me Oct 8, 2016 at 13:57
  • Here some good information about the topic. Ubuntu and Elementary can be installed in UEFI-mode. If MacOS is installed in UEFI-mode it will be less headache to install other OS in UEFI-mode too.
    – mook765
    Oct 8, 2016 at 14:03
  • @mook765 I have BIOS and the last update Dell gave was A11. Is there anything I can do to make my laptop UEFI compatible without a lot of effort? Oct 8, 2016 at 14:10
  • If the computer does not support UEFI it will be impossible to install in UEFI-mode, only legacy-mode possible. No chance to make the computer UEFI-compatible. I am not sure if you can boot from GPT-drive with this machine, I never tried that, so try and see...
    – mook765
    Oct 8, 2016 at 14:31

1 Answer 1

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Yes. Legacy can be installed on a GPT Partition Table disk format. By the way, it's the new standard that's gradually replacing MBR. This format type is a better choice because it doesn't have the MBR limits.

Read and booting to GPT Partition table drives are compatible with all Intel-based computers since 2003. It's quiet unlikely that you will find a PC that can't read the format.

Results of Copy from MBR to GPT:

I used dd to copy a partition from source drive in MBR and destination drive in GPT partition. The only partition that was affected was the destination partition on the destination drive. All the other partitions on the destination drive remained in tact.

The destination drive was a bootable drive with a GPT partition table. The OS on the 120G drive is Ubuntu 16.04. The drive boots in either a computer that has EFI compatible or just legacy. I tested booting the drive to a 10 year old Dell laptop, that only has legacy support. It booted flawlessly before the copy and after the copy to the Laptop, as my computer that has the UEFI capability.

DD Copy Script

When I perform what I consider critical task such as this, I usually create a very easy to follow script first and study it closely and run the critical command from the script. Also I have a huge command history buffer, and try to minimize accidentally running a wrong commandline from the history. I call the script from the directory with: ./ddcopy.sh

The script I used is:
ddcopy.sh:

#!/bin/bash

source="/dev/sdb1"
destination="/dev/sdc4"

read -p "Copy from device $source to $destination: [y/n] " -n 1 -r
if [[ $REPLY =~ ^[Yy]$ ]]
then
    # do dangerous stuff
    echo "..."
    echo "Proceeding..."
    time sudo dd if="$source" of="$destination" bs=4M status=progress ; espeak "Application Completed."
else
    echo "..."
    echo "Applicaton canceled."
fi

After the copy I used gparted edit's check command to correct the integrity of the partition. The two partition sizes were different. While the disk mounted and the data's checksum was correct, the check corrected the size discrepancy.

Integrity of the Files verification

I ran a checksum check of the files on the source and and the destination partitions to ensure the integrity of the files transferred. I also performed before and after checksum test of the destination drive to ensure the other partitions remained unaffected after the dd copy.

An example of the multiple checksum test is:

$ sudo mount /dev/sdb1 /mnt
$ md5sum /mnt/* >> ~/checklist2.chk ; espeak "Application completed"
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  • Hi thanks for your answer, helped a lot. One more thing, I already have Ubuntu and elemntary installs whose /home folders I want to migrate to my new GPT based installs. Would you recommend Ubuntu /home migration guide or dd? I'm confused because right now obviously the /home folders are on MBR based partitions and if I simply use the above, will it not moan about MBR to GPT transfer? Oct 8, 2016 at 13:51
  • You cannot use dd with gpt unless copying entire drive. Gpt has data in partition and that data must match data in primary & backup partition tables. You can use cp -a or rsync with various parameters to preserve ownership & permissions. With gpt you must have bios_grub partition. askubuntu.com/questions/743095/…
    – oldfred
    Oct 8, 2016 at 13:57
  • @user3677331 I have used dd often to copy partitions. Give me about an hour to make sure that I was copying between partition table types and check the effects. Oct 8, 2016 at 13:59
  • @user3677331 By the way, I usually dd my partitions to an image, then dd the image to various drives. I do this for quick distribution of new installs for clients. The image would most likely be to timely and take up too mush space for you to use a full installation. Oct 8, 2016 at 14:03
  • @user3677331 The copy from MBR to GPT went as expected. I ran a checksum on the content of the GPT existing partition before and after the copy to a different partition from the MBT. the dd copy only made changes to the destination partition. All the other partitions remained untouched. I'll update my question with broader details of the test. Oct 8, 2016 at 16:13

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