Thank you for the post.
It’s unclear from your post why the username matters at all. If using Terminal.app and the goal is to stop the FileMaker Server processes, then use the following command:
sudo launchctl stop com.filemaker.fms
This command should only require the Mac OS X admin user password to run.
Please let me know if I misunderstood the goal.
Thanks TSFalcon, that was my goal. Over the weekend I verified that my databases were still being backed up by FileMaker. That addressed my concern over corrupt databases. I stopped the server by killing it's processing on Terminal then applied the FileMaker Server Updates successfully.
After restarting I verified the databases were functioning normally.