disk utility

I had set up my MacBook Pro with Windows 8 using Bootcamp running along side a Mountain Lion OSX installation. The Bootcamp touchpad drivers for Windows 8 have not yet been fully updated so using Windows 8 is tedious to say the least, therefore I decided to remove it. So, I’m messing around with Bootcamp and removing my Windows 8 partition through Disk Utility when I get a “Partition Failed” error accompanied by the message “Couldn’t modify partition map because file system verification failed”. It appears to be a very common error when manually resizing a partition that once contained Bootcamp files, so I thought I would share how I fixed the issue incase anyone else had anything similar.

partition failed

If you have attempted to partition a drive from Mac OS X and received a “Partition failed” message with the error “Couldn’t modify partition map because file system verification failed.” you can fix the problem with the file system check command line utility. To do this properly, you’ll need to boot into Single User Mode as well:

  1. Reboot the Mac into Single User Mode by holding Command+S during boot
  2. At the command prompt, type:
    /sbin/fsck -fy
  3. When fsck is complete, type “exit” or “reboot” to reboot
  4. Boot the Mac as usual, verify the disk again in Disk Utility, and partition as usual

Simply then boot the Mac as you normally would, go into Disk Utility and resize the partition once again by sliding the box downwards to fill the unused space.

partition failurepartition failure








Simply click Apply and the process should now complete without the partition failed error.

The actual cause remains a mystery, with the partition failed error being thrown up even during a clean install bypassing Bootcamp completely and running two OSX installations. The error could also appear depending on the sequence of your clicks and drags on the partition map or some sort of calculation error.

[Source: OSX Daily]

  1. Hope it’s not too late to resurrect this discussion; I just wanted to add a few points.

    My machine is a MacBook Air 4,2 (late 2011). I’m running OS X 10.9 – rarely; more often Linux Mint 14 XFCE, booting via rEFInd. I wanted to shrink my OS X partition and use the space for a partition I could share between the two OS’s. But when I tried to shrink the OS X partition I got the “Partition failed” error.

    1. When booting via rEFInd there is no need to hold down S or . Just hit F2 when the main rEFInd screen comes up and choose Boot into single user mode.

    2. In the command prompt I typed

    /sbin/fsck -fy

    as this thread instructs.

    3. As fsck identified and repaired an error, I repeated

    /sbin/fsck -fy

    which then ran through with no errors and no repairs.

    4. I exited single user mode with exit . Boot into OS X continued, and I started diskutil and – got the same problem all over again when trying to shrink the OS X partition.

    5. After a couple such false starts I exited single user mode with reboot . This time I was able to boot into OS X, start diskutil, shrink the OS X partition and create the new shared partition (exfat).

  2. After following all these steps, still problem is existing then there are many efficient tools available like iPartition, Stellar Partition Manager with free demo version for managing Mac Drive.

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