What’s `/var/log/mariadb/mariadb.log` in centos 7?

My system is centos 7 with mariadb 5.5.60.

####LOG#### log_warnings=1 log-error=/var/log/mariadb-err.log ####slow log#### slow-query-log=1 long_query_time=5 slow-query-log-file=/var/log/mariadb-slow.log 

That ‘s all about log in my /etc/my.cnf.

I found /var/log/mariadb/mariadb.log in my server, but it’s a empty file.
What’s /var/log/mariadb/mariadb.log?

Can’t create/write to file ‘/var/log/mariadb/mariadb.log’

I’m troubleshooting a MySQL no-start on CentOS 7 VM. It is a bit unusual to see this since we have not made any configuration changes. The manual start command was taken from systemd logging. The error is the age old:

# /usr/bin/mysqld_safe --basedir=/usr 181221 17:42:49 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'. 181221 17:42:49 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql /usr/bin/mysqld_safe_helper: Can't create/write to file '/var/log/mariadb/mariadb.log' (Errcode: 13) 

According to Red Hat Bugzilla – Bug 1061045, mysql:mysql needs the appropriate permissions, which we seem to have:

[root@ftpit w]# ls -Al /var/log total 52764 ... drwxrwx---  2 mysql mysql      4096 Aug 16 11:05 mariadb 

And:

[root@ftpit w]# ls -Al /var/log/mariadb/ total 99852 -rw-rw---- 1 mysql mysql 102138776 Dec 21 17:16 mariadb.log 

And:

[root@ftpit w]# grep mysql /etc/passwd mysql:x:27:27:MariaDB Server:/var/lib/mysql:/sbin/nologin 

I also tried g-w as shown in the bug report.

Where should I look next for this error? Or how do I fix it?