http://blog.csdn.net/kumu_linux/article/details/8301760
当前shell下更改用户可打开进程数
修改limits.conf配置文件生效
[[email protected] ~]# ulimit -a //查看当前配置文件ulimit全局系数
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 1829
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) 1024
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
[[email protected] ~]# vim /etc/security/limits.conf
[[email protected] ~]# grep ‘^*‘ /etc/security/limits.conf
* soft nproc 10240
* hard nproc 10240
* soft nofile 10240
* hard nofile 10240
[[email protected] ~]#
退出当前用户，重新登录即可让之前修改的limits生效
[[email protected] ~]# ulimit -n
10240
[[email protected] ~]# ulimit -u //发现nproc并没有像nofile一样而改变
1024
[[email protected] ~]#
经google搜索获知，RHEL6下引入了配置文件/etc/security/limits.d/90-nproc.conf
（参见了@杨德华Devin 文章redhat5和redhat6 root用户不同的ulimits）
[[email protected] ~]# cat /etc/security/limits.d/90-nproc.conf
# Default limit for number of user‘sprocesses to prevent
# accidental fork bombs.
# See rhbz #432903 for reasoning.
* soft nproc 1024
[[email protected] ~]#
我们修改这个文件尝试是否因为该文件影响，修改如下
[[email protected] ~]# vim /etc/security/limits.d/90-nproc.conf
[[email protected] ~]# cat /etc/security/limits.d/90-nproc.conf
# Default limit for number of user‘sprocesses to prevent
# accidental fork bombs.
# See rhbz #432903 for reasoning.
#* soft nproc 1024
* soft nproc 65535
[[email protected] ~]#
退出当前用户，重新登录即可让之前修改的limits生效，执行如下命令发现修改成功
[[email protected] ~]# ulimit -u
10240
[[email protected] ~]# ulimit -n
10240
[[email protected] ~]#
由此可知，如果要修改配置文件limits.conf中的nproc限制上限是受文件/etc/security/limits.d/90-nproc.conf中nproc值大小制约的，但是shell终端下是不受制约的
另外笔者猜想，如果使用*号让全局用户生效是受文件/etc/security/limits.d/90-nproc.conf中nproc值大小制约的，而如果仅仅是针对某个用户，那么就不受该文件nproc值大小的影响
[[email protected] ~]# vim /etc/security/limits.d/90-nproc.conf //恢复系统默认设置
[[email protected] ~]# cat /etc/security/limits.d/90-nproc.conf
# Default limit for number of user‘sprocesses to prevent
# accidental fork bombs.
# See rhbz #432903 for reasoning.
* soft nproc 1024
#* soft nproc 65535
[[email protected] ~]# vim /etc/security/limits.conf //只针对某个用户测试（这里使用root）
[[email protected] ~]# grep ‘^root‘ /etc/security/limits.conf
root soft nproc 10240
root hard nproc 10240
[[email protected] ~]#
退出当前用户，重新登录即可让之前修改的limits生效，执行如下命令发现修改成功
[[email protected] ~]# ulimit -u
10240
[[email protected] ~]# ulimit -n
10240
[[email protected] ~]#
笔者之前猜想正确，即只有当使用*号让全局用户生效的时候，生效的nproc的值大小是受文件/etc/security/limits.d/90-nproc.conf中nproc值大小制约的，而如果仅仅是针对某个用户，那么就不受该文件nproc值大小的影响。本文链接：关于RHEL6中ulimit的nproc限制