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I am trying to copy my Photos app from my iMac (Catalina) to an external portable drive to free up space. First I got an error 36 message. I ran First Aid on both volumes, then the disk itself. The disk came back with multiple warnings -- warning: MT mapping not completely referenced. How can I resolve this to do what my original intention was...to free up space?
iMac 27″, macOS 10.15
Hi
I assume you are copying the library, and not the app. The app must stay in the applications folder.
Is the external drive correctly set up for using with a photos library?
It must be formatted APFS or MacOS extended (journaled) (preferred for spinning drives)
It Must not be (or have been) used for time machine. (A time machine drive can be used if re-formatted)
It must have the 'ignore ownership" checkbox ticked.
It should not be on a memory stick, SD or similar.
It must also not be a network drive (a direct connection is required - eg USB or Thunderbolt).
File sharing services such as iCloud Drive, Drop box, Onedrive etc are not compatible with Photos libraries.
It stands to reason that if you want any sort of reasonable performance it should be a fast drive with a fast connection.
See
Hi
I assume you are copying the library, and not the app. The app must stay in the applications folder.
Is the external drive correctly set up for using with a photos library?
It must be formatted APFS or MacOS extended (journaled) (preferred for spinning drives)
It Must not be (or have been) used for time machine. (A time machine drive can be used if re-formatted)
It must have the 'ignore ownership" checkbox ticked.
It should not be on a memory stick, SD or similar.
It must also not be a network drive (a direct connection is required - eg USB or Thunderbolt).
File sharing services such as iCloud Drive, Drop box, Onedrive etc are not compatible with Photos libraries.
It stands to reason that if you want any sort of reasonable performance it should be a fast drive with a fast connection.
See
The error -36 usually is indicating a conflict between the file system format of the destination volume and the source volume. The file system format of your external volume should be the same as the format of the system volume, but on no account should the file system format be case sensitive or you will have problems with playing videos or any container formats.
As the format of your system volume is probably APFS, move the library to an external volume formatted APFS - and respect all requirements posted by Tony. They are essential.
The warning "warning: MT mapping not completely referenced" may go away after you erase and format the external drive again with Disk Utility, but before you can format the drive you have to save all data from this drive on another drive.
Copy Photos app to external portable drive
