CentOS7的内核优化

• 修改内核配置文件

vim /etc/sysctl.conf

• 刷新配置文件

sysctl -p

• 关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

• 开启恶意的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sysrq功能

kernel.sysrq = 0

core文件名添加pid作为扩展名

kernel.core_uses_pid = 1

开SYN洪水攻击保护

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的数量默认为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

每个网络接口接收数据包速率比内核处理这些包的速率快时允许送到队列数据包的最大数目

net.core.netdev_max_backlog = 262144

限制仅仅是为防止简单的DoS攻击

net.ipv4.tcp_max_orphans = 3276800

未收到客户端确认信息的连接请求最大值

net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_timestamps = 0

内核放弃建立连接之前发送SYNACK包数量

net.ipv4.tcp_synack_retries = 1

内核放弃建立连接之前发送SYN包数量

net.ipv4.tcp_syn_retries = 1

开timewait快速回收

net.ipv4.tcp_tw_recycle = 1

允许将TIME-WAIT sockets重新用于新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

允许系统打开端口范围

net.ipv4.ip_local_port_range = 1024 65000

修改防火墙的表大小默认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

centos7内核参数优化配置详解

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 开起路由转发将0改为1即可 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

开启SYN洪水攻击保护

net.ipv4.tcp_syncookies = 1 表示开启SYN Cookies。当出现SYN等待队列溢出时，启用cookies来处理，可防范少量SYN攻击，默认为1，表示开启的； 表示SYN队列的长度，默认为1024，加大队列长度为8192，可以容纳更多等待连接的网络连接数 net.ipv4.tcp_max_syn_backlog = 262144 #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 TCP读buffer，可参考的优化值: 32768 436600 873200 net.ipv4.tcp_wmem = 4096  16384   4194304 tcp写buffer，可参考的优化值: 8192 436600 873200 net.core.wmem_default = 8388608 TCP写buffer的默认值 net.core.rmem_default = 8388608 TCP读buffer的默认值 net.core.rmem_max = 16777216 TCP写buffer的最大值 net.core.wmem_max = 16777216 TCP写buffer的最大值 #每个网络接口接收数据包的速率比内核处理这些包的速率快时，允许送到队列的数据包的最大数目 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 = 262144 net.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