linux 系统调优步骤 例
修改/etc/profile文件，加入：
ulimit -u 10240
ulimit -n 4096
ulimit -d unlimited
ulimit -m unlimited
ulimit -s unlimited
ulimit -t unlimited
ulimit -v unlimited
修改/etc/rc.d/rc.local，加入：
echo ‘131072′ > /proc/sys/fs/file-max
echo ‘131072′ > /proc/sys/fs/inode-max
(1G内存值修改成：65535 2G内存值修改成：131072 4G内存值修改成：262144)
修改/etc/sysctl.conf文件，加入：
net.core.rmem_default = 8388608
net.core.rmem_max = 8388608
net.core.wmem_default = 8388608
net.core.wmem_max = 8388608
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_sack =1
net.ipv4.tcp_window_scaling = 1
net.core.netdev_max_backlog=3000
#Modify i-node
sys.fs.file-max= 65535
sys.fs.inode-max= 65535
#Set System Memory
vm.bdflush="30 500 0 0 500 3000 60 20 0"
vm.kswapd="1024 32 64"
#Disable HackAttack!
net.ipv4.conf.eth0.accept_source_route=0
net.ipv4.conf.lo.accept_source_route=0
net.ipv4.conf.default.accept_source_route=0
net.ipv4.conf.all.accept_source_route=0
net.ipv4.conf.lo.accept_redirects=0
net.ipv4.conf.all.accept_redirects=0
net.ipv4.conf.eth0.accept_redirects=0
net.ipv4.conf.default.accept_redirects=0
net.ipv4.conf.lo.secure_redirects=0
net.ipv4.conf.all.secure_redirects=0
net.ipv4.conf.eth0.secure_redirects=0
net.ipv4.conf.default.secure_redirects=0
net.ipv4.conf.eth0.send_redirects=0
net.ipv4.conf.lo.send_redirects=0
net.ipv4.conf.default.send_redirects=0
net.ipv4.conf.all.send_redirects=0
net.ipv4.tcp_syncookies=1
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.icmp_ignore_bogus_error_responses=1
#Web Servers
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_tw_recycle=1
net.ipv4.tcp_fin_timeout=30
net.ipv4.tcp_keepalive_time=1800
net.ipv4.core.wmem_max=16777216
net.ipv4.core.rmem_max=16777216
net.ipv4.tcp_rmem="4096 87380 8388608"
net.ipv4.tcp.wmem="4096 87380 8388608"
net.ipv4.tcp_max_syn_backlog=8192
防火墙安全：
iptables -A FORWARD -p tcp --syn -m limit --limit 1/s -j ACCEPT
也有人写作
iptables -A INPUT -p tcp --syn -m limit --limit 1/s -j ACCEPT
--limit 1/s 限制syn并发数每秒1次，可以根据自己的需要修改
防止各种端口扫描
iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST RST -m limit --limit 1/s -j ACCEPT
Ping洪水攻击(Ping of Death)
iptables -A FORWARD -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT
备注说明：(相对比较激进的网络参数调整)
# Use TCP syncookies when needed
net.ipv4.tcp_syncookies = 1
# Enable TCP window scaling
net.ipv4.tcp_window_scaling: = 1
# Increase TCP max buffer size
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
# Increase Linux autotuning TCP buffer limits
net.ipv4.tcp_rmem = 4096 87380 8388608
net.ipv4.tcp_wmem = 4096 65536 8388608
# Increase number of ports available
net.ipv4.ip_local_port_range = 1024 65000