方法一：
[root@bogon ~]# vi /etc/systemd/system.conf
[root@bogon ~]# cat /etc/systemd/system.conf
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# Entries in this file show the compile time defaults.
# You can change settings by editing this file.
# Defaults can be restored by simply deleting this file.
#
# See systemd-system.conf(5) for details.
[Manager]
#LogLevel=info
#LogTarget=journal-or-kmsg
#LogColor=yes
#LogLocation=no
#DumpCore=yes
#CrashShell=no
#ShowStatus=yes
#CrashChVT=1
#CPUAffinity=1 2
#JoinControllers=cpu,cpuacct net_cls,net_prio
#RuntimeWatchdogSec=0
#ShutdownWatchdogSec=10min
#CapabilityBoundingSet=
#SystemCallArchitectures=
#TimerSlackNSec=
#DefaultTimerAccuracySec=1min
#DefaultStandardOutput=journal
#DefaultStandardError=inherit
#DefaultTimeoutStartSec=90s
#DefaultTimeoutStopSec=90s
#DefaultRestartSec=100ms
#DefaultStartLimitInterval=10s
#DefaultStartLimitBurst=5
#DefaultEnvironment=
#DefaultCPUAccounting=no
#DefaultBlockIOAccounting=no
#DefaultMemoryAccounting=no
#DefaultLimitCPU=
#DefaultLimitFSIZE=
#DefaultLimitDATA=
#DefaultLimitSTACK=
#DefaultLimitCORE=
#DefaultLimitRSS=
#DefaultLimitNOFILE=
DefaultLimitNOFILE=1024000 #这里需要修改
#DefaultLimitAS=
#DefaultLimitNPROC=
DefaultLimitNPROC=1024000 #这里也需要修改
#DefaultLimitMEMLOCK=
#DefaultLimitLOCKS=
#DefaultLimitSIGPENDING=
#DefaultLimitMSGQUEUE=
#DefaultLimitNICE=
#DefaultLimitRTPRIO=
#DefaultLimitRTTIME=
[root@bogon ~]# ulimit -a #修改之后没有重启
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 3791
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024 #还是默认值1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 3791
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
[root@bogon ~]# reboot
Connection to 192.168.1.107 closed by remote host.
Connection to 192.168.1.107 closed.
root@BP:~# ssh 192.168.1.107 #我使用的是密钥登录，所以不用再输入密码
Last login: Mon Jun 26 15:38:21 2017 from 192.168.1.100
u[root@bogon ~]# 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) 3791
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024000 #重启后生效了
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 1024000
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
[root@bogon ~]#
方法二：
ulimit只能做临时修改，重启后失效。
可以加入
ulimit -SHn 65535
到 /etc/rc.local 每次启动启用。
终极解除 Linux 系统的最大进程数和最大文件打开数限制：
vim /etc/security/limits.conf
# 添加如下的行
* soft nproc 11000
* hard nproc 11000
* soft nofile 655350
* hard nofile 655350