1.系统资源限制设置
使用ulimit -a 可以查看当前系统的所有限制值，
使用ulimit -n<可以同时打开的文件数>设置用户可以同时打开的 最大文件数
linux系统默认的只要1024
当做负载较大的服务器时，很容易遇：error: too many open files 。 并且有时候进程数太小也会导致卡死服务状态，使用ulimit -n增加 并不是永久添加，这时候就需要修改配置文件使其永久添加
ulimit
参 数：
-a 显示目前资源限制的设定。
-c <core文件上限> 设定core文件的最大值，单位为区块。
-d <数据节区大小> 程序数据节区的最大值，单位为KB。
-f <文件大小> shell所能建立的最大文件，单位为区块。
-H 设定资源的硬性限制，也就是管理员所设下的限制。
-m <内存大小> 指定可使用内存的上限，单位为KB。
-n <文件数目> 指定同一时间最多可开启的文件数。
-p <缓冲区大小> 指定管道缓冲区的大小，单位512字节。
-s <堆叠大小> 指定堆叠的上限，单位为KB。
-S 设定资源的弹性限制。
-t <CPU时间> 指定CPU使用时间的上限，单位为秒。
-u <程序数目> 用户最多可开启的程序数目。
-v <虚拟内存大小> 指定可使用的虚拟内存上限，单位为KB。
1.切换到root 权限
2.[root@HAmaster ~]# vim /etc/security/limits.conf
在最后面添加
* soft nofile 65535
* hard nofile 65535
* soft nproc 65535
* hard nproc 65535扫描二维码关注公众号，回复： 3461874 查看本文章
noproc 是代表最大进程数
nofile 是代最大文件打开数
3 [root@HAmaster ~]# vim /etc/security/limits.d/20-nproc.conf
#* soft nproc 65535
#root soft nproc unlimited
* soft nproc 65535
* hard nproc 65535
注释掉原本的 直接在下面添加，然后重启，root 和普通用户 的线程 和最大打开文件数了都是65535了
[root@HAmaster ~]# 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) 3802
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) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 65535
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
生产环境的案例：
[root@www ~]# vi /etc/security/limits.conf
# End of file
* soft core unlimit
* hard core unlimit
* soft fsize unlimited
* hard fsize unlimited
* soft data unlimited
* hard data unlimited
* soft nproc 65535
* hard nproc 63535
* soft stack unlimited
* hard stack unlimited
* soft nofile 409600
* hard nofile 409600
2.内核优化
[root@HAmaster ~]# cat /etc/sysctl.conf
# sysctl settings are defined through files in
# /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/.
#
# Vendors settings live in /usr/lib/sysctl.d/.
# To override a whole file, create a new file with the same in
# /etc/sysctl.d/ and put new settings there. To override
# only specific settings, add a file with a lexically later
# name in /etc/sysctl.d/ and put new settings there.
#
# For more information, see sysctl.conf(5) and sysctl.d(5)
根据提示 并修改 /etc/sysctl.d/99-sysctl.conf 里面的内容，增加如下内容：
#关闭ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1# 避免放大攻击
net.ipv4.icmp_echo_ignore_broadcasts = 1
# 开启恶意icmp错误消息保护
net.ipv4.icmp_ignore_bogus_error_responses = 1
# 关闭路由转发
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
#开启反向路径过滤
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1#处理无源路由的包
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
#关闭sysrq功能
kernel.sysrq = 0#core文件名中添加pid作为扩展名
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
#修改消息队列长度kernel.msgmnb = 65536
kernel.msgmax = 65536
#设置最大内存共享段大小bytes
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
#timewait的数量，默认180000
net.ipv4.tcp_max_tw_buckets = 6000
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.netdev_max_backlog = 262144
#限制仅仅是为了防止简单的DoS 攻击
net.ipv4.tcp_max_orphans = 3276800
#未收到客户端确认信息的连接请求的最大值
net.ipv4.tcp_max_syn_backlog = 262144net.ipv4.tcp_timestamps = 0
#内核放弃建立连接之前发送SYNACK 包的数量
net.ipv4.tcp_synack_retries = 1
#内核放弃建立连接之前发送SYN 包的数量
net.ipv4.tcp_syn_retries = 1
#启用timewait 快速回收
net.ipv4.tcp_tw_recycle = 1
#开启重用。允许将TIME-WAIT sockets 重新用于新的TCP 连接
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_fin_timeout = 1
#当keepalive 起用的时候，TCP 发送keepalive 消息的频度。缺省是2 小时
net.ipv4.tcp_keepalive_time = 30
#允许系统打开的端口范围
net.ipv4.ip_local_port_range = 1024 65000
#修改防火墙表大小，默认65536
net.netfilter.nf_conntrack_max=655350
net.netfilter.nf_conntrack_tcp_timeout_established=1200
# 确保无人能修改路由表
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
执行sysctl -p 是参数生效，永久生效
[root@HAmaster ~]# sysctl -p
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.tcp_max_tw_buckets = 6000
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.netdev_max_backlog = 262144
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_syn_retries = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_fin_timeout = 1
net.ipv4.tcp_keepalive_time = 30
net.ipv4.ip_local_port_range = 1024 65000
net.netfilter.nf_conntrack_max = 655350
net.netfilter.nf_conntrack_tcp_timeout_established = 1200
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0