Trying to shrink my default full disk partition to create some free space (for Ubuntu, incidentally, which I'm longing for even more now).

Partition failed
Partition failed with the error:

Couldn't modify partition map because file system verification failed

I've tried the advice here: http://osxdaily.com/2012/03/05/fix-partition-failed-error-mac/

Including booting to single user mode to run /sbin/fsck -fy and booting from the recovery partition to run disk utility to repair the disk and try partitioning there.

Verify disk seems to think everything's ok but I'm still at a loss as to how I can shrink the partition to create some free space.

1 Answer 1


Try booting from a USB drive and running Disk Utility from there on your drive, using this method in Disk Utility. You can just slide to resize the partition.

You can drag and drop

  • after to resize, how do you actually format the empty space?
    – Thufir
    Jul 16, 2018 at 19:54

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