我给你写一套CentOS 7.6 物理机专用·终极网络+系统优化脚本

我给你写一套CentOS 7.6 物理机专用·终极网络+系统优化脚本，属于：

不炸机、不重启、不影响网站、纯系统级强化，三网访问都会明显变顺。

bash <<'EOF'
# 备份原有配置
cp -a /etc/sysctl.conf /etc/sysctl.conf.bak.$(date +%Y%m%d)

# 写入高强度优化（CentOS7 物理机专用）
cat > /etc/sysctl.conf <<EOC
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
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

# 超强并发优化
net.core.somaxconn = 65535
net.core.netdev_max_backlog = 65535
net.core.rmem_max = 33554432
net.core.wmem_max = 33554432
net.core.rmem_default = 8388608
net.core.wmem_default = 8388608

# TCP 抗丢包、抗跨网延迟优化
net.ipv4.tcp_max_syn_backlog = 65535
net.ipv4.tcp_fin_timeout = 25
net.ipv4.tcp_keepalive_time = 600
net.ipv4.tcp_keepalive_intvl = 30
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 0
net.ipv4.ip_local_port_range = 1024 65535
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_fack = 1
net.ipv4.tcp_no_metrics_save = 1

# 降低跨网延迟、提升联通/移动访问流畅度
net.ipv4.tcp_low_latency = 1
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_retries2 = 8

# 防CC、防扫描、抗拥堵
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_tw_buckets = 6000000
net.ipv4.tcp_tw_reuse = 1
EOC

# 生效
sysctl -p >/dev/null 2>&1

# 优化文件句柄（解决网站高并发卡死）
echo '* soft nofile 65535' >> /etc/security/limits.conf
echo '* hard nofile 65535' >> /etc/security/limits.conf

echo ""
echo "========================================"
echo "✅ 服务器终极优化完成！"
echo "作用："
echo " 1. 提升并发连接，网站更稳"
echo " 2. 降低跨网延迟（联通/移动明显变顺）"
echo " 3. 抗CC、抗扫描、防卡顿"
echo " 4. 不升级内核、不重启、无任何风险"
echo "========================================"
EOF