Internal drive partition does not appear in Disk Utility
The internal drive in my Mac Mini has 2 partitions, A and B. I would like to modify one of the partitions, but it does not appear in Disk Utility when I select the Hitachi drive.
(When I select Macintosh HD, the partition option is grayed out but info says there are 2 partitions.)
I want to delete contents of partition A and use it for something else. It is assigned to another user, user A. Is that why I can't see it? I am user B and the superuser. I can log in as user A as well.
How can I change partition A through Disk Utility? Should I change ownership of partition A to user B?
Mac mini, macOS 10.12
