I am using macOS High Sierra.

I erased my 1 TB disk using disk utility to using Mac OS Extended (Journaled) file system.

I want to perform partition on my disk and want to split into two parts, i.e. 500 GB both.

But I am unable to do it as partition symbol is disabled in disk utility.

enter image description here

Any help would be appreciated. Thank you.

  • Other than the "boot" portion in the linked dupe question/answer, everything else is the same.
    – Allan
    May 7, 2018 at 18:18

1 Answer 1


The command below assumes the external drive is still disk3, as shown in the OP's image.

diskutil  partitionDisk  disk3  2  GPT  JHFS+  Seagate1  500G  JHFS+  Seagate2  R

This command will erase the entire contents of the external drive.

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