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

I have almost the same problem. My external HDD already has data and partition. First, the new Disk Utility interface threw me off. This is the new interface?

The HDD had 2 data partitions (160GB each), both of which I managed to erase. The third part is titled "BUFFALO Virtual CDrom Media" and has 0.8GB Uninitialised. It is an old HDD and I can't remember why it was set up like that. In all three (the two partitions as well as the Uninitialised portion), the partition is greyed out.

The other HDD I had, had two separate partitions, Backup 1 & 2, 1TB each. I erased Backup 1 but again the partition was greyed out and I am not able to further partition it or partition the entire HDD.

Sadly this wont work on my new 4TB WD drive

I tried the work around using terminal as well.diskutil erasedisk hfs+ External GPT /dev/disk2

Still nothing works?

Barry

This thread is marked as solved. Please start your own explaining exactly what your problem is.

Thank you! at first try using the command you provided I got an error so I was afraid it wasnt gonna work, but luckily when I tried again a few minutes later it did work!

I'm sorry to bother you with this silly simple question but where is the option with the model number? I'm having a tough time locating it. Thanks in advance!

Hi guys, sorry for highjacking the post, but since the problem was already solved, I thought you wouldn't mind.

I had the same problem and used the command posted here on terminal, but still can't partition my external HDD. When I run diskutil list on my terminal, this is what I get now, after using the proposed hfs+ command:

Last login: Sun Mar 27 12:28:21 on ttys000

MacBook-Air:~ TT$ diskutil list

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *121.3 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_CoreStorage Macintosh HD 120.5 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk1 (internal, virtual):

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS Macintosh HD +120.1 GB disk1

Logical Volume on disk0s2

DE906773-3685-4883-A1E5-A0D123646512

Unencrypted

/dev/disk2 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk2

1: EFI EFI 209.7 MB disk2s1

2: Microsoft Basic Data TT 999.9 GB disk2s2

MacBook-Air:~ TT$

Partition button is still greyed out. Any suggestions?

Thanks

This command deletes all of your data on your external hard drive if there's still content on it. So what I did was I used this, then I downloaded Stellar Phoenix Mac Data Recovery - instant download link <http://download.stellarinfo.com/StellarPhoenixMacDataRecovery.dmg.zip>. Run a scan and recover all the data that was on it 🙂🙂 so now you have a hard drive compatible with mac and windows, and still has all your files.

Hi guys,

came here for the same problem but turns out the solution was much more easy. You have to select the hard drive (the one with the model number) and not the line with the name that you gave the partition. Then you can partition the disk. Hope it helps.

HELP PLEASE!!!

i didn't know if I executed this command diskutil erasedisk hfs+ External GPT /dev/disk2

my hd would be erased... i lost everything, please help.... is there anything i can do to get my files back??

From hrhee0

This command deletes all of your data on your external hard drive if there's still content on it. So what I did was I used this, then I downloaded Stellar Phoenix Mac Data Recovery - instant download link <http://download.stellarinfo.com/StellarPhoenixMacDataRecovery.dmg.zip>. Run a scan and recover all the data that was on it

It works.

Leo

Same problem for me.

However, I have kept a version of Mountain Lion on another partition (internal). I booted into this partition, ran disk utility and had no problems in partitioning the external USB3.0 disk - actually a naked WD 750Gb 2.5" disk in a dock, into two partitions.

Why is it that OSX 10.8 can do trouble free, what 10.12 cannot? Surely this is a problem for Apple? Please fix this.

Tom Boone wrote:

From looking over than command it looks like this will "erase disk." Is that correct? I'm looking to keep all of the data without having to format the disk.

Yes, that's correct. The command will completely wipe your disk.

The original poster of this thread couldn't partition his external hard drive via Disk Utility. Plus there was anything at all on that disk. So I suggested to reinitialise that particular disk using Terminal.

If you are looking to RESIZE the actual partition on your disk use Disk Utility.

Use Terminal only if you are skilled enough on the command line. The resizeVolume is the correct verb to use in that case. See the below syntax

diskutil resizeVolume
Usage:  diskutil resizeVolume MountPoint|DiskIdentifier|DeviceNode size
        [part1Format part1Name part1Size part2Format part2Name part2Size
        part3Format part3Name part3Size ...]

Non-destructively resize a disk.  You may increase or decrease its size.

When decreasing size, you may optionally specify new partitions to create
to fill the newly-freed space.  Specify these new partitions as in the
diskutil partitionDisk command.  A size of zero will cause a grow fit-to-fill.
Ownership of the affected disk is required.

Valid sizes are floating-point numbers with a suffix of B(ytes), S(512-byte-
blocks), K(ilobytes), M(egabytes), G(igabytes), T(erabytes), P(etabytes),
or (%)percentage of the total size of the whole disk.

A size of "limits" will print the valid range for the current conditions of
the file system and room to grow up to an immovable object (next partition).

A size of "R" for the target partition will resize it to the maximum
possible; "R" cannot be used for the size of new partition triples, if any.

resizeVolume is only supported on a Journaled HFS+ file system.

Experiment on a disk that has no data at all on it.

If you need further assistance, please start your own thread. This one is marked as solved.

And, be sure to have a recent backup before playing around with partition 😉

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.