External drive stops backing up on Mac


If an external drive that is backing up or serving as a backup destination stops working, you may experience one or more of the following symptoms:

  • The Code42 agent may report that the backup is 100% complete, even though the external drive isn't backing up.
  • The external drive's name is appended with a "1" (for example, "USB Disk" is renamed "USB Disk 1").
  • The external drive is duplicated in your backup file selection.
  • If the drive is used as a backup destination, the Code42 agent reports Backup location is not accessible.


Code42 agent on Mac backing up an external drive, or backing up to an external drive.


This issue is typically caused by a drive that didn't cleanly unmount (for example, due to a power outage, the drive disconnected without ejecting). When this happens, the drive can leave behind a "ghost" folder in the /Volumes directory, even though the drive is no longer mounted. When the drive re-mounts, your Mac sees that the folder name for the drive is taken, so it appends a “1” to the drive name. However, the Code42 agent is looking for the folder with the original name, which is no longer valid.

To determine if you have a duplicate drive:

  1. In Finder, open Applications > Utilities > Terminal.
  2. Enter the command: cd /Volumes/
  3. Press Enter.
  4. Enter the command: ls
  5. Press Enter.

If you see the external drive name ending with a “1”, this is a duplicate drive that is causing the issue.

Recommended solution

  1. Stop the Code42 service using the stop Code42 agent command.
  2. Make sure your volume is disconnected.
  3. In the Finder, go to /Volumes.
  4. Delete the drive that is appended with 1.
  5. Reconnect your volume (it should appear in /Volumes/ without the 1 ending).
    You can check this using Terminal or the Finder.
  6. Restart the Code42 service.