Total loss of Lightroom Library.

[Rosemary Weller]

I acquired a new second iMac and started a new Lightroom Library. Six weeks later I had built a complex, many collections library of 18,00 images. Finished it 3 days ago. Did an Apple system upgrade. Next time I opened Lightroom the entire library was empty!!

There are 8 or so back-up files the largest containing 1000 images but all jumbled up amongst files.

12000 of these images are synced and they are still available on my iPad via Lightroom Mobile. How does that happen and is there any way of using that information to repopulate the  main Library?

My Preference was set to Backup when exiting Lightroom although I am sure this has not happened and now if I set the Backup box and close the preferences it will have changed if I reopen it!

Fortunately all my originals are housed in an external disc but the work in entirely rebuilding the library is

[JoeKostoss]

The most likely cause is that Lightroom opened with a new catalog.  Use Finder to locate the catalog files; search for lrcat.  Click on the ICON to open Lightroom with that catalog.  If there are more than one, try each one until the correct catalog opens.

The default path would be Pictures>Lightroom.

[Rosemary Weller]

Have opened all Lightroom icons on the system including backup files. All are either empty or contain 3 or 4 hundred empty boxes - not 18,000!!! Have now turned to WD Time Machine. Have  found what look like contending Irc. icons but cannot open them as they ask me to 'fix folder permission'. Cannot anyone help. I'm not too familiar with this. Have gone rapidly very grey!!