Does inode number remain same across file system upgrade ? ( HFS to APFS)
I am asking this question since I am using the inode number to uniquely identify the file across reboots. If inode gets changed after upgrade to APFS, functionality which relies on inode number might not work.
I observed that upgrading a HFS formatted DMG to APFS retains the inode number.
Last I checked the upgrade preserves the inode number (this produces some oddities because the inode numbers of a converted volume look very different from the inode numbers of a native volume).
I am asking this question since I am using the inode number to uniquely identify the file across reboots.
There’s two ways to look at this:
If you’re tracking a small number of files, you should use a bookmark. This handles lots of edge cases that are otherwise difficult to deal with (for example, it will work across backup and restore).
If you’re tracking a vast number of files, storing a bookmark for each is going to be too expensive. In that case using the inode number is fine, but you have to have a way to deal with the inode numbers becoming invalid (for example, the above-mentioned backup and restore case).
A good example of the latter is Spotlight. Its index uses the inode number to keep track of files, but it is able to rebuild this index if things goes south.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"Thanks Quinn for detailed reponse. I would probably have to use inode number in that case and deal with restore/backup cases, as I process large number of files.