After upgrading to macOS Catalina 10.15, or installing a subsequent 10.15.x update, the auto_master file will be overwritten. You may need to re-append any custom lines to auto_master after the upgrade to restore your previously-working automounts.
Post-upgrade (or update), check the automount master mapping file (/etc/auto_master) to verify that your previously-working lines were removed.
sudo nano /etc/auto_master
The default contents probably look something like this:
# # Automounter master map # +auto_master # Use directory service #/net -hosts -nobrowse,hidefromfinder,nosuid /home auto_home -nobrowse,hidefromfinder /Network/Servers -fstab /- -static
Optionally, save a backup copy of this original for future reference (and for quick restoration after each Catalina minor upgrade):
cd /etc sudo cp auto_master auto_master.original
Now, append any lines you previously used to reference your other auto_* files. In my case, I have only one file named auto_nas.
Save your changes and then run the automount command to flush the cache and reload /etc/auto_master:
sudo automount -vc
Look for confirmation that each share mounted successfully:
automount: /System/Volumes/Data/Nas/media mounted automount: /System/Volumes/Data/Nas/storage mounted automount: /System/Volumes/Data/Nas/archives mounted
If you happen to be mounting any shares into the /System/Volumes/Data/ directory, make sure you have updated your mountpoints to match Catalina’s new directory structure. Otherwise, automount will complain about the mount point not existing.