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数据库版本：5.5.14

操作系统版本：contos 6.3

服务器256G内存，安装90个实例。通过脚本启动90个mysql数据库实例，会有几个实例无法启动，进程启动后直接被杀死。查看mysql日志如下：

140729 10:32:34 [ERROR] Can't create thread to kill server
140729 10:46:35 mysqld_safe Starting mysqld daemon with databases from /export/data/mysql/data3363
140729 10:46:36 InnoDB: The InnoDB memory heap is disabled
140729 10:46:36 InnoDB: Mutexes and rw_locks use GCC atomic builtins
140729 10:46:36 InnoDB: Compressed tables use zlib 1.2.3
140729 10:46:36 InnoDB: Initializing buffer pool, size = 1.0G
140729 10:46:36 InnoDB: Completed initialization of buffer pool
140729 10:46:36 InnoDB: highest supported file format is Barracuda.
InnoDB: Error: pthread_create returned 11
140729 10:46:37 mysqld_safe mysqld from pid file /export/data/mysql/data3363/mysql.pid ended
140729 10:48:26 mysqld_safe Starting mysqld daemon with databases from /export/data/mysql/data3363
140729 10:48:26 [ERROR] setuid: Resource temporarily unavailable
140729 10:48:26 [ERROR] Aborting

主要问题是系统资源限制导致，可通过修改:
[root@yoon ~]# ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 2066313
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65535
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1024
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

可是ulimit修改后，不是永久性的。网上说在vi /etc/security/limits.conf下添加如下：
* soft nofile 65535
* hard nofile 65535
* soft nproc 65535
* hard nproc 65535

但是最终发现，也不是永久性的。而是要在此参数下修改，vi /etc/security/limits.d/90-nproc.conf
*          soft    nproc     65536
并手动ulimit-u 65535  即可。