I'm used to backup my user's home using rsync. However, I now have data (eg, running database) that shouldn't be backed up while being changed, and I'd like to keep the applications changing them running during the backup.

I know file system snapshot views exist to deal with this problem: Linux has the LVM approach and Apple has Time Machine. However, apparently only the former allows one to mount a snapshot as a virtual file system, so that it's possible to use tools like rsync, tar, or, for what matters, cp, against a view of the files frozen at a given time.

I cannot find any such feature for macOS, tmutil/Time Machine don't look to be the same thing, they must be leveraging the snapshot functionality of their APFS file system, but I can't find any way to see a snapshot as a set of files. Is that possible for APFS?

Note that I'm not interested at all in using Time Machine for my backups: I'm an advanced user and TM is too stupid to suit me fine (it doesn't work over SSH, it doesn't allow me to select a folder on a destination device, it doesn't seem to support multiple backup profiles, each with a different set of sources/destinations and different schedules), nor I'm so interested in spending money on things like SuperDuper!, just to do what that my scripts have done very well for years.


Yes, it is definitely possible to view an APFS snapshot as a "set of files" - i.e. a file system. This is done simply by mounting the snapshot - exactly like you would do with LVM on Linux.

The syntax is:

  mount_apfs -s <snapshot name> <mounted base volume> <mount folder>

So for example create a snapshot with:

  tmutil snapshot /

It will say that the new snapshot is named for example: 2019-01-01-180510.

Then later you can create a folder "MyBackup" and mount the snapshot like this:

  mount_apfs -s com.apple.TimeMachine.2019-01-01-180510 / MyBackup

If you then browse MyBackup you'll see the files like they were at the time the snapshot was taken.

Note: You don't have to use snapshots created by TimeMachine. Any APFS snapshots will be mountable with the same command.

  • Thanks a lot @jksoegaard, just tried it and works perfectly! I see there are tmutil alternatives (eg, arstechnica.com/gadgets/2017/02/…), but that's a minor issue for me.
    – zakmck
    Jan 1 '19 at 17:16
  • 1
    Note that the alternative (fs_snapshot) isn't available to ordinary users. Only certain developers can actually take advantage of it.
    – jksoegaard
    Jan 1 '19 at 17:18

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