Can't partition (option greyed out) External HDD on Mac OS X El Capitan

I solved this issue by using Disk Utility by going up to the Menu bar, selecting "View", and selecting "Show All Devices". Then, the erase and partition buttons became active. I didn't have to get into Terminal at all.

I solved this issue by using Disk Utility by going up to the Menu bar, selecting "View", and selecting "Show All Devices". Then, the erase and partition buttons became active. I didn't have to get into Terminal at all.

Thank you so much and I wish I had found your answer yesterday! I spent so much time before finding your solution that worked. After following your instructions and pressing partition from the main listing of my hard drive in disk utilities, I got a message saying I needed to click the external option of my hard drive (which was the listing under the main hard drive) "file" and "enable journaling." After doing that the partition option was no longer greyed out and I was able to successfully partition the drive.

Issue the following Terminal's command

diskutil erasedisk hfs+ External GPT /dev/disk2

PQ:

NP. I did too, at first.

Go back a page and find eunicekhong's post. it has an image of the Disk Utility window we're talking about. Look at the left column, at the very first entry, at the top of the column. It looks something like: APPLE SSD SM0256G Media. (that is my HD, not the one by eunice, but I didn't want to go back a page and lose this msg.)

see it?

OK Ihad to reformat back to OS journaled to solve this then it allowed the partitioning.

It will not allow it to partitioned in EXFAT

Barry

Your terminal output indicates that it has not been formatted correctly for HFS+

Make sure that you select the GUID partition and not the MBR which is for FAT. Thereafter your disk should be formatted correctly for HFS+

Leo

Apple doesn’t routinely monitor the discussions. These are mostly user to user discussions.

Send Apple feedback. They won't answer, but at least will know there is a problem or a suggestion for change. If enough people send feedback, it may get the problem/suggested change solved sooner.

Feedback

The fact the disk utility is now an abortion in comparison to its past incarnations, have to enter a command line to partition a disk? 3 disks in the machine now I have to enter another command to determine which disk identifier then cross my legs I don't screw everything up? - tell you what why dont I start using CPM again? that was a command line the whole point about macos is one GUI to rule them all, not a dumbed to do to uselessness heap, resorting to command lines is a failure apple I'm continuously disgusted with you nowadays F**ple, sierra is awful. disk utility in 10.4/10.5 was far superior this is ******** retrograde.

I tried the suggested Terminal command and got this:

Last login: Tue Jan 31 12:28:11 on ttys000

RobertscBookPro:~ robertxxx$ diskutil erasedisk hfs+ External GPT /dev/disk2

Started erase on disk2

Unmounting disk

Creating the partition map

Waiting for partitions to activate

Formatting disk2s2 as Mac OS Extended with name External

Initialized /dev/rdisk2s2 as a 465 GB case-insensitive HFS Plus volume

Mounting disk

Finished erase on disk2

RobertscBookPro:~ robertxxx$

To no avail, I still have the PARTITION icon dimmed.

This is the info of the external Samsung SSD T3

Volume name : External

Volume type : Physical Volume

BSD device node : disk2s2

Mount point : /Volumes/External

File system : Mac OS Extended

Connection : USB

Device tree path : IODeviceTree:/PCI0@0/XHC1@14

Writable : Yes

Is case-sensitive : No

File system UUID : 1B65CCC5-5FD0-34D9-AC1C-90C51234C0B0

Volume capacity : 499,763,888,128

Available space (Purgeable + Free) : 499,357,732,864

Purgeable space : 0

Free space : 499,357,732,864

Used space : 406,155,264

File count : 53

Owners enabled : Yes

Is encrypted : No

System Integrity Protection supported : No

Can be verified : Yes

Can be repaired : Yes

Bootable : No

Journaled : No

Disk number : 2

Partition number : 2

Media name :

Media type : Generic

Ejectable : Yes

Solid state : No

Parent disks : disk2

What can I do to partition the SSD?

Robert

oh thank you so much, had to tell it,

such a drag from apple, unbelievable, getting always worse!!

thank s again, after days only this worked, or reformatting on a PC

(one day I want to know how did you know)

thank s again

Hi, Alberto!

I stupidly pasted the 'diskutil erasedisk' command into Terminal without checking my disk device labels 😕

The erase process started immediately and began erasing the disk I did not mean it to.

I cancelled/terminated the process within 10 seconds.

The disk is now showing as empty in Disk Utility. It also won't eject properly. A TimeMachine backup was being made at the same time I used the command.

How quick does the 'diskutil erasedisk' command work and do you think there's any chance that the disk has not been (entirely) erased?

Thank you 🙂

This identical terminal command worked with my Lacie 1TB drive that showed up as 272.6 GB after using Disk Utility and Erase... (formatting either at MAC OS or MS-DOS [FAT]).

After running the terminal command the drive shows up as 999.86 GB, and now the partition button is active in Disk Utility. Thanks, much!

sundy_1 wrote:

Hi guys,

Scoured the net for an existing solution to this problem, but to no avail.

I'm attempting to partition a 500gb external HDD to run bootcamp, but whenever I go into Disk Utility, the option to partition the drive is greyed out.

I've previously erased and formatted to Mac OS X Journaled, so there's nothing on it, but still the partition option isn't available (see screenshot).

Any help is majorly appreciated. Thanks in advance!

This drive has been formatted as FAT (MS-DOS), for Microsoft. You have to erase it, to give it a new partition table. (GUID for OS X Journaled)

Leo