systemd error with user having a dot (.) in name: Invalid user/group name or numeric ID

Linux Ubuntu 18. MariaDB service fails to start throwing a systemd error. The reason seems to be that the userid contains a dot (.).

systemd[1]: Invalid user/group name or numeric ID: myuser.withdot

Configuration:

The service file from MariaDB is /etc/systemd/system/mariadb.service.d/migrated.conf, and it contains:

[Service]  User=myuser.withdot  

https://stackoverflow.com/questions/67238600/systemd-error-with-user-having-a-dot-in-name-invalid-user-group-name-or-num April 24, 2021 at 09:37AM