I’m not a systemd guru, but it turned out pretty easy. dev.mysql.com/doc/refman/…/using-systemd.html#sys… Basically just make [mysqld@copy] sections in my.cnf then systemd start mysqld@copy and systemd is smart enough to pass copy into mysql.

I did it slightly different, using systemctl edit mysql@.service to define different default files for each instance, then [mysqld@copy] sections in each of those files. Seems like the port option for each has to go in a [mysqld] section, but otherwise ok.

Replication because I want to put some live data, read-only, on the VPS, exposed to the world while the ‘real’ database stays safely hidden in my intranet. SSH tunnel so the replica can talk to the real database.