Upgrading to Yosemite so I can install the newest version of xCode.
Shortly after starting I get this error:

A mismatch between the MBR and GPT partition maps is not supported with this operation. Quit the installer to restart your computer and try again.

I've tried going into Disk Utility and repairing permissions, but even though it says it's repairing things, when I run it again the same errors show up.

Not sure what to do here.

Edit: Disk Manager

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Edit 2: GPT and FDisk:

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Edit 3: in response to n1000

Command (? for help): v

Warning! Mismatched GPT and MBR partition! MBR partition 4, of type 0x07,
has no corresponding GPT partition! You may continue, but this condition
might cause data loss in the future!

Identified 1 problems!

Command (? for help): ?
b   back up GPT data to a file
c   change a partition's name
d   delete a partition
i   show detailed information on a partition
l   list known partition types
n   add a new partition
o   create a new empty GUID partition table (GPT)
p   print the partition table
q   quit without saving changes
r   recovery and transformation options (experts only)
s   sort partitions
t   change a partition's type code
v   verify disk
w   write table to disk and exit
x   extra functionality (experts only)
?   print this menu

Command (? for help): r

Recovery/transformation command (? for help): ?
b   use backup GPT header (rebuilding main)
c   load backup partition table from disk (rebuilding main)
d   use main GPT header (rebuilding backup)
e   load main partition table from disk (rebuilding backup)
f   load MBR and build fresh GPT from it
g   convert GPT into MBR and exit
h   make hybrid MBR
i   show detailed information on a partition
l   load partition data from a backup file
m   return to main menu
o   print protective MBR data
p   print the partition table
q   quit without saving changes
t   transform BSD disklabel partition
v   verify disk
w   write table to disk and exit
x   extra functionality (experts only)
?   print this menu
  • so you are able to boot your previous system right now?
    – n1000
    Aug 4, 2015 at 19:20
  • 2
    What are you upgrading from and how is the disk partitioned? What OSes are installed if more then whatever version of OS X you're trying to upgrade from? Are you running a third party boot manager? Aug 4, 2015 at 19:24
  • @user3439894 Upgrading from 10.9.5. I have a bootcamp partition with windows 8.1 on it. I'm just using the boot manager that came with the OS. I'm adding a screenshot of disk manager
    – AndyD273
    Aug 4, 2015 at 19:31
  • @n1000 Yeah, I was able to quit the installer and choose to boot to the old OS.
    – AndyD273
    Aug 4, 2015 at 19:52
  • Please add to the OP the output of the following two commands in aTerminal. Copy and paste as one command then press Enter: sudo gpt -r -vv show disk0; sudo fdisk /dev/disk0 Aug 4, 2015 at 19:54

1 Answer 1


This post explains the procedure. Now is probably a good time to make a backup. Then proceed at your own risk...

  1. Get gdisk
  2. In Terminal: sudo gdisk /dev/disk0
  3. Press v to verify your MBR
  4. Press r and then o to list the MBR partition table
  5. Press m and then p to display the GPT partition table information
  6. Compare the numbers for partition 4 from the MBR and GPT tables. The start numbers should match, but the end numbers will probably be off.
  7. Press d to delete the GPT partition 4 (Bootcamp). "Note: this does not delete the actual partition from disk. It only deletes gdisk's in-memory representation of the GPT."
  8. Press n to create a new partition 4 (Bootcamp) using the start and end sector values from the MBR partition 4
  9. Change the name of the new partition 4 to BOOTCAMP
  10. Press v to verify
  11. If no errors occurred: press w to write the new partition table
  12. If errors occurred: press q and try again
  13. Reboot

The important part is step 7 where you sync your GPT and MBR. Note that some of the commands (e.g. disk0, partition 4) may be different in your case. Please adapt them accordingly.

  • Before doing this make sure you are properly backed up! :) Aug 4, 2015 at 20:06
  • @user3439894 good point :)
    – n1000
    Aug 4, 2015 at 20:09
  • With step 4, r takes you into recovery and transformation options (experts only) mode, and step 5 m takes you back into normal mode. I posted the output of v, as well as the two help menus in case what I downloaded is different than what you have...
    – AndyD273
    Aug 5, 2015 at 15:32
  • Figured it out. Steps 4 and 5 were missing the parts where print tables was actually chosen, instead of just entering the menu and then leaving it again. I updated the instructions to put the necessary commands.
    – AndyD273
    Aug 6, 2015 at 16:48
  • @AndyD273 Does that mean you were able to upgrade to Yosemite? Great!
    – n1000
    Aug 6, 2015 at 19:31

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