I have used the mount command to mount non-primary drive storage in to my the file system on my primary hard drive. So the path /remote-mounts/some-directory actually places me on a USB-attached drive when I change in to it.

Will Time Machine traverse in to the mounted directories and back them up or does it stop at mount points? Is it smart enough to tell that these mounts aren't actually on my primary drive?

Edit: Here's my personal exclusion list with a USB drive mounted. As you can see STUFF is excluded automatically and I can't prevent that. It's un-selectable in the list.

Personal exclusion list with a USB drive mounted

  • 1
    The vast majority (all) drives I've seen attached via USB or FireWire or thunderbolt show up as fair game. Since yours is showing more like a disk image I'm curious about the details. Does diskutil list show any hints about this mount or this drive?
    – bmike
    Jun 1, 2012 at 22:40
  • I'll try to revisit this later today and remember how I had it set up, answer you question. IIRC "STUFF" was probably FAT32. It was a USB stick.
    – Ian C.
    Jun 2, 2012 at 15:56

2 Answers 2


It's most likely your filesystem is just one that fseventsd is ignoring due to it not being HFS+

Even with a proper Mac filesystem, you could have unintentionally told the system to secure and ignore this volume by having an obscurely documented empty file called no_log in /path/to/your/fs/.fseventsd/no_log.


Open Time Machine and see if the USB drive is on the Excluded List. Time Machine normally takes any external drive and automatically puts it on the Excluded List, If you see it there, remove it from the excluded list and it will be backed up.

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    I added a screen shot of the exclusion list with a USB drive mounted. Lion won't let you remove it from the exclusion list.
    – Ian C.
    Mar 28, 2012 at 16:40
  • This answer should work for most cases so we'll have to dig to see why the drive isn't seen - my guess would be a non-GPT volume or perhaps a non HFS+ volume format so that fseventsd cannot grok the files for backup.
    – bmike
    Jun 1, 2012 at 22:42

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