MacOS – how to create a 128MB HFS+ partition using diskutil

I've run in to this before and the only solution I'm aware of is to reformat your file system. Here's what I suggest you do:

1. Boot off of your OSX install media and use Disk Utility to clone your OS image on to another drive.

2. Reformat your main drive with the file system you want

3. Restore the contents of your backed-up system to the main drive.

You could also go largely through Time Machine for this, but I'd recommend going straight at Disk Utility. TimeMachine refuses to restore from backups that have a different case-sensitivity setting.

Here's a random link to someone's article on cloning a drive with Disk Utility.

First I have to explain the gpt result:

The partition with index 1 is your EFI partition. The partitions with index 2 and 3 are your main OS X volume named Macintosh HD (also visible in the second screenshot) and your Recovery HD. The partition with the index 4 is your NTFS volume WinB (also visible in the second screenshot).

Trying to add a new partition (by using the +-button) or to resize Macintosh HD (by using the handle) with Disk Utility will downsize partition 2 and move partition 3 to the new end of partition 2.

Since adding a new partition with the +-button doesn't work properly for you, you have two options:

• use the handle and resize Macintosh HD. This should create unallocated free space

• or use the +-button and create a new volume. Apparently it will be formatted as a HFS+ Journaled volume.

  • Then boot to Internet Recovery Mode and open Terminal.
  • Enter diskutil list and gpt -r show /dev/disk0.
  • Unmount your main disk with diskutil umountDisk /dev/disk0.
  • Remove the new HFS+ volume with gpt and its index number found above:
    gpt remove -i 4 disk0
  • Enter exit and quit Terminal
  • Reboot

This might break Boot Camp as stated in Disk Utility and is not recommended if Windows boots in MBR-mode. So backup your Mac (including the Bootcamp partition) first.

I tested this with a spare MacBook Air (Mid 2013 with a 250 GB SSD) and a vanilla Yosemite after installing Windows 8.1 R1. Regardless what I did, I had no problem to boot from either Windows 8.1 or OS X. Windows 8.1 seems to be booted in EFI-mode though.

Since you have an older Mac, Windows will probably be booted in hybrid MBR-mode. Adding a fourth partition (at position 3) will break bootability of the last one because only three partitions (and the EFI partition) are allowed.