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APFS: Don't Create Before...

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NOTTING HILL (Rixstep) — This was detected when preparing further tests for our new Swap.app application on APFS with Catalina.

The idea was to stress-test how 'swaps' work with files from different directories.

A simple script was copied into two test directories, 'a', and 'b'.

Here's the Info sheet for the first file.

Here's the Info sheet for the second file.

Note that:

  • The paths differ, as do the inodes - those are two separate files.
  • The 'created' timestamps are not only identical but also two years back in time.

Some timestamps are intentionally programmable on Unix, but the 'created' timestamp is not one of them. That stamp is supposed to be generated at creation time in the kernel.

The 'created' field for the original file proved to be the same.

Although there can be an explanation for the 'tidy' stamp in the original, such as it perhaps being created on an earlier HFS volume where those fields were not properly protected, 'created' timestamps aren't supposed to apply in file copy operations. And they should not propagate to new copies on the same APFS volume.

Digging further into this bizarre behaviour unfortunately raises more new questions than provides answers. See below for links to further information. According to Apple, data integrity's not high on the list of priorities?

See Also
DTrace: APFS in Detail: Data Integrity
ACP Guru: Swapping on APFS with Catalina
iPhone 6 owners reporting boot loops and crashes

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