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Photos: error code -42 when copying .photoslibrary to an external drive

I want to copy (or move) my Photos Library (50 Gb, about 16'000 photos) to another external drive.

After about 80% copying time this error occurs in Mojave 10.14.4.

How do I resolve this issue?

Thank you in advance!

iMac 27", macOS 10.14

Posted on May 31, 2019 7:40 AM

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Question marked as Top-ranking reply

Posted on Jun 4, 2019 4:29 AM

Hi léonie,

Your suggestion worked!

I copied all folders within .photoslibrary on the NAS to a new empty folder on a Mac OS formatted external drive one-by-one.

Then I renamed this folder to 'something.photoslibrary'.

Opening it in Photos resulted in an error message about inconsistencies and offering to repair the library which I did.

After a few minutes my 55'000 picures showed up and seem to be accessible as before on the NAS.

Thank you for your suggestion!

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6 replies
Question marked as Top-ranking reply

Jun 4, 2019 4:29 AM in response to léonie

Hi léonie,

Your suggestion worked!

I copied all folders within .photoslibrary on the NAS to a new empty folder on a Mac OS formatted external drive one-by-one.

Then I renamed this folder to 'something.photoslibrary'.

Opening it in Photos resulted in an error message about inconsistencies and offering to repair the library which I did.

After a few minutes my 55'000 picures showed up and seem to be accessible as before on the NAS.

Thank you for your suggestion!

Jun 1, 2019 12:00 AM in response to bloggie43

Is the destination drive used for Time Machine backups? Then you cannot move a Photos Library there because of permission problems.

You did not yet tell us, if the "Ignore Ownership on this volume" flag is available for the destination USB drive as shown in the screenshot posted by OT? Did you enable it?


Copying between drives with different filesystem formats may result in copy errors, because the supported filenames may differ, for example, if if one drive is case-sensitive and the other not.


I hope, the solution to copy the library with PowerPhotos will work.

If not, you try to identify the file, that is causing the read/write error. You can do that, by copying the subfolders of the library separately.

This way you can see how far the copy got, before the error occurred. The first file that did not copy will be the culprit.

  • To open the library package select the library in the Finder and Ctrl--click it.
  • Select "show package contents".
  • Then create a new, empty folder on your external drive and drag the folders from the library one-by-one into the new folder.
  • If a copy error occurs, check the destination drive, how far the copy succeeded. The next file to be copied, is probably causing the error. Skip it.
  • Once the library has been copied, rename the folder with the copy to "Photos Library.photoslibrary". Now the icon of the copy should change from the folder icon to the Photos Library icon.
  • Try to open the copy in Photos by double clicking it.




Jun 4, 2019 3:12 AM in response to Old Toad

Hi Old Toad,

There was no other Library except for the one on the NAS.

I checked with the folks at Fat Cat Software for a solution with PowerPhotos but they do not support copying Photolibraries on drives other than formatted with Mac OS.

So I followed the idea of léonie (see below) but there was another obstacle...

Thanks for your input!

Photos: error code -42 when copying .photoslibrary to an external drive

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