TimeMachine on El Capitan can not see new TM volume on Catalina.
As it says on the tin, TimeMachine on our ElCap 10.11.6 Macs does not recognize the TimeMachine volume we created on our MacMini running Catalina 10.15.7. We shared the HFS+ disk as AFP & SMB and selected "Share as a Time Machine destination" in Advanced Settings:
When we open TimeMachine on either of our El Capitan Macs they can not see the drive listed when we click Select Disk....
We can see the TM volume as a selectable destination on my High Sierra MacBook Pro.
in 2017 robinhood4 reported success in getting ElCap to see a TM drive shared on a High Sierra Mac, but his share-folder-instead-of-drive suggestions did not work for us. (https://discussions.apple.com/thread/8141537?answerId=8141537021#8141537021)
We also tried the manual Terminal method we found here:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
sudo tmutil setdestination -a "/Volumes/TMfolder/"
but got this reply:
/Volumes/TMfolder: Destination does not support F_FULLSYNC. (error 45)
The backup destination could not be added.
Not much luck in figuring out why a drive or folder shared as a TimeMachine destination does not support F_FULLSYNC. We tried changing the share protocol for the drive to AFP only but it made no difference.
We had this working previously when the MacMini was running Sierra, but hardware problems caused to to be replaced with a newer Mini that is able to run the newer versions of MacOS that are actually supported. Yes, we know ElCap is no longer Apple-supported but we don't have the $$$$$ to replace our MacPro that tops out with ElCap.
Thank you for any reasonable suggestions.
MacBook Pro