同步时间

yum -y install ntp
/usr/sbin/ntpdate cn.pool.ntp.org

禁用SELinux

# 临时禁用
setenforce 0
# 永久禁用
sed -i 's/=enforcing/=disabled/' /etc/sysconfig/selinux
sed -i 's/=enforcing/=disabled/' /etc/selinux/config

# 查看（原先：Enforcing，设置后：Permissive）
getenforce

关闭防火墙

systemctl stop firewalld
systemctl disable firewalld

systemctl status firewalld
systemctl list-unit-files | grep firewalld

内核生产环境优化参数

参考1：CentOS内核参数优化参考
 参考2：Centos 7系统优化脚本
 参数3：linux内核参数注释与优化

cat >> /etc/sysctl.conf << EOF
net.ipv4.tcp_syn_retries = 1
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_keepalive_time = 600
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.tcp_keepalive_intvl =15
net.ipv4.tcp_retries2 = 5
net.ipv4.tcp_fin_timeout = 2
net.ipv4.tcp_max_tw_buckets = 36000
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_max_orphans = 32768
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_wmem = 8192 131072 16777216
net.ipv4.tcp_rmem = 32768 131072 16777216
net.ipv4.tcp_mem = 786432 1048576 1572864
net.ipv4.ip_local_port_range = 1024 65000
net.core.somaxconn = 16384
net.core.netdev_max_backlog = 16384
EOF
/sbin/sysctl -p

不生效（CentOS Linux release 7.8.2003 (Core)）
net.ipv4.ip_conntrack_max = 65536
net.ipv4.netfilter.ip_conntrack_max=65536
net.ipv4.netfilter.ip_conntrack_tcp_timeout_established=180