Mariadb on Centos 7 not changing max connections based on my.cnf
You might find that the limit is not where you think.

I've had trouble with open file limits and that's set by Centos itself.
Please see:

How to permanently raise ulimit 'open files' and MySQL 'open_files_limit'

Some key points from that link:


The default ulimit on open files is 1024.
MySQL sets its open_files_limit to whatever the system's ulimit is set to.
MySQL cannot set it's open_files_limit higher than ulimit.


You can raise the ulimit temporarily or permanently, globally or for specific users; see the link for details.

There are more resources like that around.