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I have an external NTFS hard drive that I am trying to mount on my Mac. It was working fine until I inadvertedly unplugged it before properly ejecting.

I can see the disk with diskutil:

/dev/disk3 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *2.0 TB     disk3
   1:               Windows_NTFS ⁨disk_name               2.0 TB     disk3s1

I tried the following command with the (disapointing) following outputs:

$ diskutil mount /dev/disk3
Volume on disk3 timed out waiting to mount

$ diskutil verifyDisk /dev/disk3 Unable to verify this whole disk: A GUID Partition Table (GPT) partitioning scheme is required (-69773)

N.B. I have another USB drive that works fine with a Windows_NTFS partition. Moreover, the disk mounts without any problem on a Windows computer, meaning I can see the content of the hard drive without problems.

EDIT

I ran chkdsk with the following output:

PS D:\> chkdsk
The type of the file system is exFAT.
Access is denied.

The volume is in use by another process. Chkdsk might report errors when no corruption is present. Volume Serial Number is **-** Windows is verifying files and folders... Volume label is name_of_drive. Windows found errors on the disk, but will not fix them because disk checking was run without the /F (fix) parameter. Corruption was found while examining the volume bitmap. File and folder verification is complete.

Windows has checked the file system and found problems. Run CHKDSK with the /F (fix) option to correct these.

1953247232 KB total disk space. 1588895104 KB in 3138236 files. 674688 KB in 1671 indexes. 0 KB in bad sectors. 2048 KB in use by the system. 363675392 KB available on disk.

131072 bytes in each allocation unit.

15259744 total allocation units on disk. 2841214 allocation units available on disk.

I then ran the following chkdsk /F with the following output:

PS D:\> chkdsk /F
The type of the file system is exFAT.
Cannot lock current drive.

Chkdsk cannot run because the volume is in use by another process. Chkdsk may run if this volume is dismounted first. ALL OPENED HANDLES TO THIS VOLUME WOULD THEN BE INVALID. Would you like to force a dismount on this volume? (Y/N) y Volume dismounted. All opened handles to this volume are now invalid. Volume Serial Number is **-** Windows is verifying files and folders... Volume label is name_of_drive. Corruption was found while examining the volume bitmap. File and folder verification is complete.

Windows has made corrections to the file system. No further action is required.

1953247232 KB total disk space. 1588895616 KB in 3138237 files. 674816 KB in 1672 indexes. 0 KB in bad sectors. 2048 KB in use by the system. 363674752 KB available on disk.

131072 bytes in each allocation unit.

15259744 total allocation units on disk. 2841209 allocation units available on disk.

It worked (The disk could finally be mounted in my Mac)!!

ecjb
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  • Not properly ejecting drives can cause terminal errors. You may want to check out the answers here: https://apple.stackexchange.com/q/293390/237687. But you might end up having to reformat, partition and restore the data from your backup. – Solar Mike Sep 05 '22 at 12:25
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    What happens if you run chkdsk on the Windows PC? Does that find any errors or make it mountable on the Mac? – Steve Chambers Sep 05 '22 at 22:08
  • thanks for your comment @SteveChambers. I will try that today. Shall I write this command in powershell (and if yes what would the be pattern to use as I am not a regular windows user)? In the meantime: I have now two additional external disk that were properly working and suddenly are not working anymore! – ecjb Sep 07 '22 at 08:15
  • Ok @SteveChambers , I tried the command chkdsk on Powershell and I got the following: Windows cannot check a disk attached through a network. I suppose this is because this is the PC of my workplace which is attached to a central server – ecjb Sep 07 '22 at 12:41
  • By "external drive I am trying to mount on my Mac" I assumed a USB (or some such) drive plugged directly into your Mac. If it is a network drive that is VERY different and troubleshooting would start on the device it is shared from (Server, NAS, etc...) – Steve Chambers Sep 07 '22 at 12:48
  • @SteveChambers. Yes you assumed correctly: it us a USB drive plugged on the Mac. The only available pc I have is the one at work (which is connected by default to a remote server). So I guess I would have to go to the external drive through the pc but this is where my powershell knowledge comes to a limit – ecjb Sep 07 '22 at 13:07
  • @SteveChambers: I could finally run the chkdsk command (and copied the output in the edited question): it found some error. I am running now chkdsk /F – ecjb Sep 07 '22 at 13:13
  • Well it seems that powershell Window could solve the problem that Mac could solve (Sic!!)! My Mac is at home so I'll check it out in an hour – ecjb Sep 07 '22 at 13:19
  • It worked!! Thanks @SteveChambers Windows! Bottom line: the problem was caused on a Mac, could not be solved on a Mac but could on Windows... Many thanks – ecjb Sep 07 '22 at 13:59
  • Rule one of file system repair, only do it on the platform that the filesystem is native on. Mac: HFS/APFS, Windows: FAT/NTFS, Linux: EXT (plus the hundred others...) – Steve Chambers Sep 08 '22 at 16:27

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