directory structure of Time Machine backup

Question

directory structure of Time Machine backup

I have a harddrive connected to a ASUS router (in turn connected to a google wifi mesh) which I use as my TimeMachine backup disk.

Everything is working as expected but I am not understanding the directory structure that I see via finder.

I am attaching it here.

Under RT-AC68U-2120 (the ASUS "server") I see a folder called backups.backupdb.

Under backups.backupdb I see the following

antonella's Macbook Pro.sparsebundle

and

antonella's Macbook Air are the TM backups

But what is CNID?

why is there another Backups.backupdb under CNID?

If I try to delete CNID it says it cannot because Backups.backupdb is in use. There is nothing under Backups.backupdb

Thanks!

MacBook Pro 13″, macOS 10.14

Posted on Jun 12, 2020 9:18 PM

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Answer 1

Jun 13, 2020 10:30 AM in response to mamma_antonella

mamma_antonella wrote:

Thanks for your answer, but this was not my question. I am not asking how to use TimeMachine or how to access it. I want to know why the structure on disk is the way I see it!

I do not like black boxes. I like the Terminal a lot.

A good way to corrupt your TM is to manually start poking around and trying to make changes via the Finder.

Unlike other protocols like SMB or NFS, the AFP protocol mostly refers to files and directories by ID and not by a path (these IDs are also called CNID, Catalog Node ID.) The "concurrent database" back-end is based on Berkeley DB. With this back-end, several afpd daemons access the CNID database directly. Berkeley DB locking is used to synchronize access, if more than one afpd process is active for a volume. This back-end is also used internally (as in-memory CNID database) as a fallback in case opening the primary database can't be opened, because tdb (Samba's Trivial Database) can work as in-memory database.

This of course means upon restart the CNIDs are gone.

Set the protocol for file sharing on Mac - Apple Support

Network address formats and protocols on Mac - Apple Support

Share files on your Mac with other devices - Apple Support

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Answer 2

Jun 13, 2020 7:08 AM in response to mamma_antonella

Time machine is best to interface through the TM interface, not the Finder.

How to use Time Machine to... restore your Mac: https://support.apple.com/en-us/HT201250

Use Time Machine to restore deleted files or older files - Apple Support https://support.apple.com/en-us/HT209152

Restore items backed up with Time Machine on Mac - Apple Support https://support.apple.com/guide/mac-help/restore-files-mh11422/mac

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Answer 3

Jun 13, 2020 7:28 AM in response to leroydouglas

Thanks for your answer, but this was not my question. I am not asking how to use TimeMachine or how to access it. I want to know why the structure on disk is the way I see it!

I do not like black boxes. I like the Terminal a lot.

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Answer 4

Jun 13, 2020 1:45 PM in response to leroydouglas

Thank you very much. I have no intention of messing up with TM via the finder, but I do not like not understanding what I am seeing.

I have used the same configuration before and I do not remember seeing the CNID directory. This is why I was surprised.

Thanks.

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directory structure of Time Machine backup

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