在linux中执行ulimit -a 即可查询linux相关的参数，默认情况下，linux最大文件句柄数为1024个。当你的服务器在大并发达到极限时，就会报出“too many open files”。
[root@mongodb11 ~]# 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) 256324 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 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) 256324 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
ulimit -n 2048这命令就可以修改linux最大文件句柄数，修改以后使用ulimit -a 查看修改的状态，但是，这种方法只针对当前进程有效。重新打开一个shell或者开启一个进程，你就会发现参数还是ulimit -n xx修改之前的数字。那么有没有一劳永逸的方法呢？
修改linux系统参数。vi /etc/security/limits.conf 添加
* soft nofile 65536
* hard nofile 65536
修改以后保存，注销当前用户，重新登录，执行ulimit -a ,ok ,参数生效了。
备忘录
echo ' * soft core unlimit' >>/etc/security/limits.conf echo ' * hard core unlimit' >>/etc/security/limits.conf echo ' * soft fsize unlimited' >>/etc/security/limits.conf echo ' * hard fsize unlimited' >>/etc/security/limits.conf echo ' * soft data unlimited' >>/etc/security/limits.conf echo ' * hard data unlimited' >>/etc/security/limits.conf echo ' * soft nproc 102400' >>/etc/security/limits.conf echo ' * hard nproc 102400' >>/etc/security/limits.conf echo ' * soft stack unlimited' >>/etc/security/limits.conf echo ' * hard stack unlimited' >>/etc/security/limits.conf echo ' * soft nofile 409600' >>/etc/security/limits.conf echo ' * hard nofile 409600' >>/etc/security/limits.conf sysctl -p