Centos 7 内核优化

禁用SELINUX

<pre>

grep -i ^selinux /etc/selinux/config

SELINUX=enforcing
SELINUXTYPE=targeted
</pre>

修改最大进程数和最大文件打开数

ulimit -n和-u可以查看Linux的最大进程数和最大文件打开数

在文件最末尾添加
<pre>
cat >> /etc/security/limits.conf << EOF
* soft nofile 1024000
* hard nofile 1024000
* soft nproc 1024000
* hard nproc 1024000
EOF
</pre>

说明：
'*' 代表针对所有用户
noproc 是代表最大进程数
nofile 是代表最大文件打开数

还需要修改/etc/security/limits.d下面的conf文件(会覆盖前面的配置信息)，我的是20-nproc.conf
<pre>
cat /etc/security/limits.d/20-nproc.conf

Default limit for number of user's processes to prevent

accidental fork bombs.

See rhbz #432903 for reasoning.

* soft nproc 4096
root soft nproc unlimited
</pre>
修改为：
<pre>
cat /etc/security/limits.d/20-nproc.conf

Default limit for number of user's processes to prevent

accidental fork bombs.

See rhbz #432903 for reasoning.

* soft nproc 1024000
* hard nproc 1024000
</pre>

内核优化

vi /etc/sysctl.d/99.sysctl.conf

<pre>

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

开启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 = 2

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

vm.max_map_count=655360

</pre>