Within disk utility, the partition icon is grayed out. If I mouse over it, it reads: "Disks with Master Boot Record Partition Maps cannot be partitioned". The history on this drive: It is a 2 TB Seagate external hard drive that the Mac store reformatted for me to use with Time Machine. I had a problem right after I bought my Mac and we did this to backup my machine and literally restore it to a new machine. Since then, I have used it with time machine and now want to re-partition it so I can store backups of additional files to the other partition (once it is created). The current single partition is "Mac OS Extended (Journaled)". Any ideas how to address this issue? I would prefer not to have to erase the disk as part of the process (if possible).
Mac OS Sierra – Disk Utility will not let me partition an external hard drive
disk-utilityhard drivepartitiontime-machine
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Best Answer
I've just encounter the same problem, where Partition icon is grayed out. I found the solution.
Simply launch this command in terminal and the partition icon will not be grayed out anymore :
For clarity, in the above command, the path argument starts from
/dev
, not "External GPT "However, this command will erase the disk, make a backup if needed before !
Source : Apple Discussion - Alberto Ravasio