We recently changed the domain of our filer due to this few users have lost permissions to their CIFS shares. Is there a way to get the fsecurity show output from some config file, so that i can proactively check for the changes before and after domain change.
There's no saved config for permissions. The best you might manage is - if you've snapshot copes, the snapshots may have different permissions. It depends if they're inherited or share level permissions though.