If you are using Stardog free (the community edition), you might want to upgrade to the current version - 8.1 - and get the benefit of the new features and improvements. The default user for a free standalone version is admin, with password admin.
Thanks for your reply. I am not running free edition. I am running latest Stardog on premise installed on Linux. It maybe that instructions are not complete. So I am still awaiting for a Stardog engineer to chime in.
When you install Stardog via deb/rpm, the stardog user is created as a part of that process. If you look in your /etc/passwd file you should see an entry for this user:
This is the user as which the stardog process runs, so it will need to be the owner of /var/opt/stardog or at least have read/write permissions on it. If you hadn't previously created that directory to use as the home directory, it will also have been created during the install with the proper permissions.
No, you can run the systemctl command with any user provided it has the correct permissions to do so. As defined in /etc/systemd/system/stardog.service, the server start command will be run as the stardog user.