Whenever I try to resize my OSX partition on my SDD from 251GB to 210GB, I get this error:

Couldn’t modify partition map because file system verification failed.

I've tried

  • Booting into recovery mode and trying from disk utility there (repairing and partitioning)
  • Booting into single-user mode and running fsck -fy like seemingly every website suggests

but whenever I try to do this in any situation, I still get this error. This is frustrating because AFAIK only OS X knows how to resize an OS X partition.

How can I get around this?


  • Apple Diagnostics gave no errors.
  • I first had this error when I had filevault (full disk encryption) turned on. I have since turned off FileVault and repaired any errors I caused by trying to partition the encrypted disk with Disk Utility in recovery mode. I have checked again that FileVault is off, and it is.


$diskutil list
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            248.4 GB   disk0s2
   3:                 Apple_Boot Recovery HD             1.7 GB     disk0s3
$ diskutil cs list
No CoreStorage logical volume groups found
  • run AHT to check.
    – Ruskes
    Nov 13 '14 at 6:24
  • I just ran Apple Diagnostics, which replaces AHT on newer macs, it said there were no issues. Nov 13 '14 at 6:48
  • Please add the output of diskutil list and diskutil cs list executed in Terminal to your question.
    – klanomath
    Nov 13 '14 at 10:09
  • @klanomath added. Nov 14 '14 at 0:26

In order to change the size of a partition, the partition can't have any errors.

The easiest way to repair the partition is to reboot while holding Cmd+R, and start the Disk Utility from the menu that is presented after the recovery system has started.

Then select the partition and click the 'Repair Disk' button. After it has finished, it should say that there are no more errors. The partition can now be resized.

NOTE: Unfortunately, because of HFS+ it is possible that Disk Utility may display "Could not be repaired", at which point you would need to reformat the drive and restore from your latest backup. I hope this is not the case!

  • I tried this, it said it repaired successfully, and then I get the same error when trying to partition. Nov 13 '14 at 6:43
  • Did you try to do the partitioning while booted from the Recovery partition? Nov 13 '14 at 6:51
  • Yes, and that failed too. Nov 13 '14 at 6:52
  • For some reason my recovery mode and things like it are in spanish, but it was the same error message as far as I could tell. Nov 13 '14 at 6:52
  • I just tried this again, and I got the same error. Nov 13 '14 at 7:00

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