i have a VPS which i recently rebuilt onto centos7.
the mariadb service starts fine upon initial installation and securing, however, after reboot, the service will not start, stating no access to pid file in /var/run/mariadb/whaterver.pid.
owner on /run/mariadb get reset to root:root instead of staying mysql:mysql after reboot.
i even tried a script on /etc/tmpfiles.d/mariadb.conf which does:
d /var/run/mariadb 0755 mysql mysql -
this script does appear to create the directory but owner always changes to root:root after reboot completes.
I ended up 'fixing' this issue by manually mapping the pid-file=/var/lib/mariadb/mariadb.pid and setting permissions to mysql:mysql on /var/lib/mariadb
i've also found that i cannot enable selinux, and firewalld commands do not work.
my local lab/dev version of cos7 with minimal install and a duplicated wordpress does not have any of these issues.