The following shell command sequence makes me realize I don't understand something very basic about how user and group accounts works on MacOS:
/tmp$ cd /usr/local/mysql/data
/usr/local/mysql/data$ ls -l | grep mydatabase
drwxrwxrwx 55 _mysql _mysql 1760 Jun 24 2019 mydatabase
/usr/local/mysql/data# su xxxx
su: unknown login: xxxx
/usr/local/mysql/data# su _mysql
summary: The file system shows that the mysql installation created a user account and group account both called: "_mysql". Yet, when I am root, and "su" that account, I remain the root user.
why do I care? I ran my database fine using El Capitan. Then, I upgraded to Catalina, and now I'm having trouble (I think permission) with running mysqld. And, as a general "best practice", I think you are suppose to minimize the number of things running as root on your machine, yet _mysql and root sort of look like the same account. Of course, I really just want my db running again and understanding the _mysql could lead to this.