MySQL max_open_filesが1024を超えています。

MariaDBを起動すると、[警告] Max_open_filesの数を1024以上に増やすことはできません（要求：4607）というメッセージが表示されます。

$ sudo systemctl status mysqld
● mysqld.service - MariaDB database server
  Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled)
  Active: activating (start-post) since Tue 2014-08-26 14:12:01 EST; 2s ago
Main PID: 8790 (mysqld);         : 8791 (mysqld-post)
  CGroup: /system.slice/mysqld.service
      ├─8790 /usr/bin/mysqld --pid-file=/run/mysqld/mysqld.pid
      └─control
    ├─8791 /bin/sh /usr/bin/mysqld-post
    └─8841 sleep 1

Aug 26 14:12:01 acpfg mysqld[8790]: 140826 14:12:01 [Warning] Could not increase number of max_open_files to more than 1024 (request: 4607)

このファイルのmax_open_files問題を解決しようとしましたが、成功しませんでした。

$ sudo nano /etc/security/limits.conf 
mysql           hard    nofile          8192
mysql           soft    nofile          1200

コンピュータを再起動しても同じ問題が発生しました。

/etc/mysql/my.cnf は次のようになります:

[mysql]

# CLIENT #
port                           = 3306
socket                         = /home/u/tmp/mysql/mysql.sock

[mysqld]

# GENERAL #
user                           = mysql
default-storage-engine         = InnoDB
socket                         = /home/u/tmp/mysql/mysql.sock
pid-file                       = /home/u/tmp/mysql/mysql.pid

# MyISAM #
key-buffer-size                = 32M
myisam-recover                 = FORCE,BACKUP

# SAFETY #
max-allowed-packet             = 16M
max-connect-errors             = 1000000
skip-name-resolve
sql-mode                       = STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_AUTO_VALUE_ON_ZERO,NO_ENGINE_SUBSTITUTION,NO_ZERO_DATE,NO_ZERO_IN_DATE,ONLY_FULL_GROUP_BY
sysdate-is-now                 = 1
innodb                         = FORCE
innodb-strict-mode             = 1

# DATA STORAGE #
datadir                        = /home/u/tmp/mysql/

# BINARY LOGGING #
log-bin                        = /home/u/tmp/mysql/mysql-bin
expire-logs-days               = 14
sync-binlog                    = 1

# CACHES AND LIMITS #
tmp-table-size                 = 32M
max-heap-table-size            = 32M
query-cache-type               = 0
query-cache-size               = 0
max-connections                = 500
thread-cache-size              = 50
open-files-limit               = 65535
table-definition-cache         = 1024
table-open-cache               = 2048

# INNODB #
innodb-flush-method            = O_DIRECT
innodb-log-files-in-group      = 2
innodb-log-file-size           = 128M
innodb-flush-log-at-trx-commit = 1
innodb-file-per-table          = 1
innodb-buffer-pool-size        = 2G

# LOGGING #
log-error                      = /home/u/tmp/mysql/mysql-error.log
log-queries-not-using-indexes  = 1
slow-query-log                 = 1
slow-query-log-file            = /home/u/tmp/mysql/mysql-slow.log

max_open_filesの問題を解決するには？