mysql_install_db with umask 007 doesn't work work when datadir is a directory nested inside /var/lib/mysql. To test it, the datadir /var/lib/mysql/node1/databases has been used. mariadb@.service has UMask=007 and the service in SUSE Linux Enterprise Server runs mysql_install_db on the datadir set in the configuration file.

This can be translated to:

ExecStartPre=/usr/bin/mysql_install_db --datadir=/var/lib/mysql/node1/databases

The error in /var/log/mysql/mysqld.log is:

[ERROR] mysqld: Can't create/write to file '/var/lib/mysql/node1/databases/aria_log_control' (Errcode: 13 "Permission denied")

It stops half-way when it is creating the database. The same command outside of systemd works so the issue is umask.