I modified three files to fix an error which max_connection is fixed to 214.
/etc/pam.d/common-session
session required pam_limits.so
session optional pam_ck_connector.so nox11/etc/security/limits.conf
* hard nofile 24000
* soft nofile 32000/etc/my.cnf
...
[mysqld]
max_connections = 1024
wait_timeout = 30
open_files_limit = 24000
...