I'm currently on 10.10.5 and I want to partition my internal SSD into two, installing a fresh copy of 10.12 on the second partition (while keeping 10.10.5 on the original partition). I want to eventually delete the original partition on the SSD that the mac shipped with (10.10.5), leaving only the second partition of 10.12.

Doing a search, it seems it may not be possible to make a second partition the only partition.

Will Disk Utility allow me to delete the original partition? and will it allocate the full amount of regained space to the new partition?

  • Rather than putting an answer as an edit of your OQ, I suggest you to make an answer.
    – dan
    Oct 1, 2016 at 10:26

3 Answers 3


I've solved this problem by taking a completely different approach. I used Disk Utility to clone my internal SSD onto a new partition on an external SSD. I am now going to restore my internal SSD back to factory (by restarting, then CMD + R), then update it to 10.12. This way there is only a single partition with a fresh install of 10.12 on the internal SSD. I will still have my old bootable install of 10.10.5 and files on the external SSD, in case I need to access files or restore it back completely.


Resizing the boot partition is a bit tricky - because you can't do it whilst booted from it.

If you want to avoid getting your hands dirty in Terminal, the old way to do it used to be iPartition, but it's getting a bit old these days & can't deal with Core Storage drives. The new kid on the block seems to be Paragon Hard Disk Manager, which I have but haven't yet used for this particular task. It's also capable of moving Boot Camp partitions around, should you ever have need of that.

For either, you need to be booted from another device. iPartition would make boot CDs, iirc, but Paragon can make boot USB keys; which I have used successfully.

Once you have two potential boot partitions, deleting either is just a reverse of your initial task, & being an SSD, the actual location of the data is unimportant, unlike on a spinning disk.

Maybe wait a day or two to see if anyone comes up with the alternative Terminal method - which of course is free - or give Paragon a test drive; I think their demo is fully-functional [though I haven't tested the demo, I went straight for the full version]


Indeed you can and in some cases that is how it has to been done. I believe adding El Capitan to a partitioned drive required such..

Once OS is installed.

Open Disc Utility > Select the HD in the left panel > Click on the partition to delete on the graph > Click the minus - button at the bottom.

  • From searching, it seems you can not use this method on the original partition or any partition with a lower sector number than the new partition (the minus button - with be greyed out).
    – Martin
    Oct 1, 2016 at 5:50
  • Apart from the fact it won't let you, deleting the existing boot partition wasn't the first task; resizing it & adding a second partition was what the OP asked.
    – Tetsujin
    Oct 1, 2016 at 7:40

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