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So the situation is as follows, I have a 2TB external USB drive partitioned into 2 halves, 1TB each. The first half was used for Time Machine, and the 2nd half a generic ext. USB HD.

Midway through a Time Machine backup the drive ejected itself and I got the "Disk was not ejected correctly" message. This seems to have broken the TM partition as it doesn't appear in Disk Utility, or System Info, or the Desktop.

The 2nd half however does appear on the desktop, and I can check the info and see I have used 250GB etc, but it can't be opened, and won't appear in Disk Utility, or under the USB section of sys info.

It seems then that the 2nd partition is fine (of sorts), however the first half is broken, and stopping the 2nd being read/written etc. I don't mind loosing the Time Machine backups as I have taken a spare on another drive, but I do need the data from the 2nd half.

Does anyone know how I might go about deleting just the broken partition, not using Disk Utility (as its not visible)?

EDIT This is the results of diskutil list, and its disk1s2 that I think is causing the issue.

Timothys-Mini-2:~ timothywilkinson$ diskutil list
/dev/disk0 (internal, physical):
#:                       TYPE NAME                    SIZE      IDENTIFIER
0:      GUID_partition_scheme                        *500.1 GB   disk0
1:                        EFI EFI                     209.7 MB   disk0s1
2:                  Apple_HFS Macintosh HD            428.6 GB   disk0s2
3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
4:                  Apple_HFS Recovery HD             70.5 GB    disk0s4

/dev/disk1 (external, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *2.0 TB     disk1
1:                        EFI EFI                     209.7 MB   disk1s1
2:                  Apple_HFS                         1.0 TB     disk1s2
3:                  Apple_HFS External HD             999.9 GB   disk1s3
  • The Disk Utility application does not show every partition. However, the command line version does. So could you post the output from the command diskutil list to you question? You will need to open a Terminal application window in order to enter this command. – David Anderson Mar 18 '18 at 0:12
  • Thank you for the tip, yes it does appear there as disk1s2, I have edited the question accordingly. – Tim Wilkinson Mar 18 '18 at 0:31
  • See my answer here How can I delete a partition (coreStorage logical volume?) from the Terminal. Same principle applies to normal partitions. – njboot Mar 19 '18 at 3:17
  • Thank you for the idea but it doesn't work. I have no coreStorage Logical Volumes, and whilst it may be the same for normal partitions, force unmount fails. – Tim Wilkinson Mar 19 '18 at 17:00
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I know this sounds insultingly simple, but have you completely unplugged and powered down the external drive and plugged it back in?

At the office, TM would periodically decide that the time machine disk was damaged and could not be written to. Restarting didn't fix it, even though it was mountable. Removing power to the device and plugging it back in fixed it and allowed it to be written to again. In both of the cases, they were LaCie drives. Give it time after plugging in, it could be doing a disk repair in the background before it shows on the desktop (can be verified by looking in activity monitor.)

  • Thanks for the answer, and I should have included it in my OP but yes this has been done. Different port, cable, on and off etc. – Tim Wilkinson Mar 18 '18 at 23:13

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