xtrabackup备份MySQL报错：InnoDB: Error number 24 means 'Too many open files'

1.使用xtrabackup备份MySQL时出现如下报错：

 :: >> log scanned up to ()

xtrabackup: Generating a list of tablespaces

InnoDB: Allocated tablespace ID  for mysql/plugin, old maximum was

InnoDB: Operating system error number  in a file operation.

InnoDB: Error number  means 'Too many open files'

InnoDB: Some operating system error numbers are described at http://dev.mysql.com/doc/refman/5.7/en/operating-system-error-codes.html

InnoDB: File ./jira/AO_4B00E6_STASH_SETTINGS.ibd: 'open' returned OS error . Cannot continue operation

InnoDB: Cannot continue operation.

2.查看备份使用的user的ulimit

[root@linux mysql]# ulimit -a

core file size          (blocks, -c)

data seg size           (kbytes, -d) unlimited

scheduling priority             (-e)

file size               (blocks, -f) unlimited

pending signals                 (-i)

max locked memory       (kbytes, -l)

max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024

pipe size            ( bytes, -p)

POSIX message queues     (bytes, -q)

real-time priority              (-r)

stack size              (kbytes, -s)

cpu time               (seconds, -t) unlimited

max user processes              (-u)

virtual memory          (kbytes, -v) unlimited

file locks                      (-x) unlimited

3.修改/etc/security/limits.conf

vim /etc/security/limits.conf

* soft nofile 

* hard nofile

重新备份还是报错。

4.修改MySQL的配置文件，增加如下参数：

vim /etc/my.cnf

innodb_open_files=