What determines ownership of Tomcat's catalina.out?

Solution 1:

The logs are created when Tomcat is started by systemd, ie. root. Then, for safety reasons, the process changes ownership.

The catalina.out log is a PITA, for someone interested in rotating it. There is no way except when restarting Tomcat. When I was running Tomcat, I made sure the standard output was kept to a minimum, by forcing the developers to take good care of the logging of their applications. Whenever they missed something, it ended up in catalina.out.