I have an iMac running El Capitan, and an external disk formatted NTFS that will not mount on the mac. It will mount perfectly in Windows and Ubuntu.

I'm not trying to write to it, right now I just want to read.

Here's my output of "diskutil mount disk3s1":

Volume on disk3s1 failed to mount
If the volume is damaged, try the "readOnly" option

Output of info:

Device Identifier:        disk3s1
Device Node:              /dev/disk3s1
Whole:                    No
Part of Whole:            disk3
Device / Media Name:      Untitled 1

Volume Name:              

Mounted:                  No

File System Personality:  NTFS
Type (Bundle):            ntfs
Name (User Visible):      Windows NT File System (NTFS)

Partition Type:           Windows_NTFS
OS Can Be Installed:      No
Media Type:               Generic
Protocol:                 USB
SMART Status:             Not Supported
Volume UUID:              E6F4FA18-C794-465E-82A1-91A8F45C4262

Total Size:               320.0 GB (319965626368 Bytes) 
(exactly 624932864 512-Byte-Units)
Volume Free Space:        0 B (0 Bytes) (exactly 0 512-Byte-Units)
Device Block Size:        512 Bytes

Read-Only Media:          No
Read-Only Volume:         Not applicable (not mounted)

Device Location:          External
Removable Media:          No

Any ideas would be appreciated.

  • 1
    Since you're using NTFS I'll assume you have a Windows system that you can attach the external drives to and run chkdsk /f <drive letter>: on from an Administrator Command Prompt, e.g., chkdsk /f e: and then try mounting again under OS X. This will ensure there are no issue with the filesystem, which under some circumstances may cause it not to mount properly. – user3439894 Dec 29 '15 at 20:45
  • I've done that, and encountered the same problem. – Nick Dingman Dec 29 '15 at 23:53
  • Are you running the newest version of OS X? – captaindogfish Dec 30 '15 at 0:10
  • I'm running, 10.11.1 – Nick Dingman Jan 4 '16 at 18:25

I was getting the above error and a suis premount dissented error. I was eventually able to mount it by with:

sudo /sbin/mount_ntfs /dev/disk3s1

In some cases, when an external drive works on Windows but doesn't on Mac OS, it's because you didn't eject it properly. All you need to do is connect it to a Windows OS, and eject it properly (through the devices icon near the Windows clock).

For more information and screenshots for these instructions, look into this article which was the source for how I fixed a similar problem.


I was also getting a similar error message: failed to mount: "SUIS premount dissented". I did the following to resolve this:

  1. Created a new folder External-HDD, for example in /Volumes: sudo mkdir /Volumes/External-HDD
  2. Opened up diskutility.app and noted the Device name for the external HDD. disk3s2, for example. (I wasn't able to mount it using DiskUtility.app)
  3. Also note the filesystem for external HDD in DiskUtility: USB External Physical Volume • ExFAT
  4. In terminal issue the following command:

sudo /sbin/mount_[filesystem type] /dev/[device name] /Volumes/[your folder]

Sample command:

sudo /sbin/mount_exfat /dev/disk3s2 /Volumes/External-HDD/

OS: macOS Mojave (10.14.6)

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