I use an iMac as an external monitor for my MacBook pro (OS X 11.6), over a thunderbolt cable. I usually have a USB 3 hard drive attached to my MacBook pro as a Time Machine backup. Last week I thought I would try attaching my USB drive to my iMac, and mounting it as a shared network drive over the thunderbolt network bridge. Of course, Time Machine then created a .sparsebundle disk image to perform the backup over the network. I decided I didn't want to start a full backup from scratch, and so moved the USB drive back to a direct connection.

However, now Time Machine only wants to back up to the .sparsebundle image, even thought the drive is connected locally and has a full set of backups at the root of the drive (in Backups.backupd). I tried using tmutil setdestination and tmutil associateddisk -a to force the association, with no success. I even renamed the .sparsebundle, and every time I start a backup the .sparsebundle is renamed back to the old name.

How can I stop Time Machine from treating the USB-attached hard drive as a network share for backups?

2 Answers 2


In order to prevent Time Machine from continuing to use the created .sparsebundle for its backups, you need to delete it.

Time Machine tries to backup to .sparsebundle files first. If it can't find any, it will create regular local backup.


What you want isn't really how it works. See, .sparsebundle files are basically treated as though they're a separate disk. So the OS/Time Machine basically sees the sparsebundle as essentially being a separate disk from the disk it's actually on - "moving" from one to the other isn't a simple task, and certainly couldn't be done reliably by you unless you had deep intricate knowledge of how Time Machine works, and probably you'd need some UNIX skills as well. Your best bet is to probably just turn Time Machine off, delete the sparsebundle file on the disk, turn Time Machine back on and let it re-create the backups for you.

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