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Question:

Question: How can I covert a MBR to GPT partition map?

Mi imac don't restart after the 10.8.4 update, and the solution is reinstall OSX restoring the HD.

i'm using a external hard drive to clone the content of my HD, but its a MBR partition map, and it says that the process can only be done with a GPT partition map.


anyone who knows how to convert from a MBR to a GPT with a mac?

after converting the external HD, may i change again the partition map to his native MBR partition?


Many thanks.

iMac, OS X Mountain Lion (10.8.4)

Posted on Jun 13, 2013 1:30 PM

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Question marked as Solved
Answer:
Answer:

Drive Partition and Format


1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.


2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.


3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed.


4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.


5. Set the format type to Mac OS Extended (Journaled.) Click on the Security button, check the button for Zero Data and click on OK to return to the Erase window.


6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.


You can change the drive back to MBR by repartitioning it once again. Change GUID to MBR and the format to MSDOS on the Mac or do the same on a PC.

Posted on Jun 13, 2013 1:34 PM

Question marked as Solved

Jun 13, 2013 1:34 PM in response to MauTerenzi In response to MauTerenzi

Drive Partition and Format


1. Boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.


2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.


3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed.


4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.


5. Set the format type to Mac OS Extended (Journaled.) Click on the Security button, check the button for Zero Data and click on OK to return to the Erase window.


6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.


You can change the drive back to MBR by repartitioning it once again. Change GUID to MBR and the format to MSDOS on the Mac or do the same on a PC.

Jun 13, 2013 1:34 PM

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Apr 4, 2014 9:09 AM in response to MauTerenzi In response to MauTerenzi

Sorry Kappy but you answer is absolutely not on his question he ask about converting not reformatting disk that is two totally different things.

Here is answer how to do that without of lost any info which you already have on your disk.


http://www.computerknow.org/2013/09/changing-mbr-to-gpt-in-mac-os-x.html


Milan

Apr 4, 2014 9:09 AM

Reply Helpful (3)

Apr 4, 2014 9:35 AM in response to Csound1 In response to Csound1

I have same problem with converting MBR on my disk and this tool from link which i post help me in solving problem without lost any info. I have lot of date on my disk and for me is critical to change GPT because i want to crypt my disk and as you know crypt disk work only GPT, of course that link i post procedure is not trivial and not for novice, but that help me and work in my case.

if I am not wrong question is

How can I covert a MBR to GPT partition map?

critical word is convert not reformat/repartitioning that is two totally different things.


Regards,

MIlan

Apr 4, 2014 9:35 AM

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Apr 4, 2014 9:49 AM in response to Csound1 In response to Csound1

I have problem with crypt my disk yesterday and i try to found solution how to do that, and found this discussion first and only after 30 min or so link which i post. Today i try solution from that link and found that information can be very useful to people like me who want to convert MBR on there disk not reformat/repartitioning, because of that i post on already solved for other people like me who find this link first.


Milan

Apr 4, 2014 9:49 AM

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Jan 27, 2015 9:23 AM in response to Csound1 In response to Csound1

I'm actually glad that Millan posted that response. These discussions live on well after the OP asserts that it solved their specific problem. Often times, new information becomes available making the original answer less viable. I was Googling "mac os x convert mbr to gpt" and cam to this thread. I wasn't particularly interested in reformatting my disk and Millan's answer was more in line with what I was looking for. Not to mention, we've had 2 releases of OS X in the time frame that this post was initially created. So, there's likely newer information that yields a more efficient solution to the original problem.


I'm not sure why this upsets you so much. This information is here for the community and not just the individual posters. Clearly you haven't spend enough time in other forums like StackOverflow, etc..

Jan 27, 2015 9:23 AM

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Jan 27, 2015 9:43 AM in response to Ryan J. McDonoughj In response to Ryan J. McDonoughj

BTW, another super simple way to do this in Yosemite is to use Core Storage and Diskutility. If you run diskutil like so:


diskutil corestorage list


You likely won't see the volume in question, or see no volumes at all. To conver it, you need to know the volume name (such as "Macintosh HD") and run the following:

diskutil corestorage convert "Macintosh HD"


This will convert it GPT. It shouldn't take very long to do. To verify, run:


diskutil corestorage list


You should see your volume listed there. For it to fully take effect, restart Mac OS X. No reformatting or additional tools required.


Ryan-

Jan 27, 2015 9:43 AM

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Jan 27, 2015 9:44 AM in response to Ryan J. McDonoughj In response to Ryan J. McDonoughj

Ryan J. McDonoughj wrote:



I'm not sure why this upsets you so much. This information is here for the community and not just the individual posters. Clearly you haven't spend enough time in other forums like StackOverflow, etc..

Because it is an unsafe procedure which once again (thanks to you) bubble to the top again.

Jan 27, 2015 9:44 AM

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Apr 9, 2015 3:45 AM in response to Csound1 In response to Csound1

Csound1... Registered just to tell you how annoying people like you are.


Others: better formatted, same article: http://superuser.com/questions/495672/how-can-i-convert-a-mbr-partition-to-gpt-w ithout-loss-of-data


You will need gpart boot cd: http://gparted.org/livecd.php


Have fun micromanaging the internet XD

Apr 9, 2015 3:45 AM

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Apr 9, 2015 4:05 AM in response to schonkeren In response to schonkeren

Others: better formatted, same article: http://superuser.com/questions/495672/how-can-i-convert-a-mbr-partition-to-gpt-w ithout-loss-of-data


Though in my case (macbook pro late 2011) I had to use "sudo gdisk /dev/sda" (it's Linux after all XD). Because I moved a 500GB HDD to 250GB SSD, I had resized partitions (Paragon Hard Disk Manager Pro 2015) which now gave an extra error of overlapping partitions... I ignored that and continued with the advised 'w'rite and 'q'uit to save the MBR to GPT conversion - without data loss).


Then I immediately rebooted with Apple-sign R to load Internet Recovery's Disk Utility. This way I could fix the filesystem errors (caused by *any* conversion it seems 🙂) to finally reboot into my cloned Mac OS X...


You will need gpart boot cd: http://gparted.org/livecd.php

Apr 9, 2015 4:05 AM

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Apr 9, 2015 4:49 AM in response to schonkeren In response to schonkeren

Ok, I should not have dismissed the warning about overlapping partitions. The problem actually was 1MB of free space left after the main OS partition (and before the backup). I resized (with gparted) the backup partition with 1MB to get rid of the last bit of freespace.


(Use c to boot from cd.)


I restarted gdisk command, all was ok now (except for MBR warning).

I chose 'w'

A warning appears: Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING PARTITIONS!! Proceed? (Y/N)

I chose 'Y' - with scare though ;p

Operation completed successfully.


Don't forget to Apple-R for Disk Utility ...


And sorry for the bad responding mousepad in Linux... 😐

Apr 9, 2015 4:49 AM

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Apr 9, 2015 5:14 AM in response to schonkeren In response to schonkeren

schonkeren wrote:


Csound1... Registered just to tell you how annoying people like you are.


Others: better formatted, same article: http://superuser.com/questions/495672/how-can-i-convert-a-mbr-partition-to-gpt-w ithout-loss-of-data


You will need gpart boot cd: http://gparted.org/livecd.php


Have fun micromanaging the internet XD

Why would I need gpart?


Long day?

Apr 9, 2015 5:14 AM

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User profile for user: MauTerenzi

Question: How can I covert a MBR to GPT partition map?