CentOS刚安装后的优化处理

1、首先默认关闭掉selinux和iptables

set -i ‘s/SELINUX=enforcing/SELINUX=disabled/’/etc/selinux/config 
setenforce 0 
getenforce #查看现在selinux的状态 
/etc/init.d/iptables stop #停止防火墙 
chkconfig iptables off #开机不启动防火墙 
chkconfig --list | grep iptables #查看防火墙状态

2、更改ssh登录时的端口号

vi /etc/ssh/sshd_config
......................
port 22              #改为自己希望的端口号
.....................
UseDNS yes,改为UseDNS no    
#连接时会自动检测dns环境是否一致导致的，修改为不检测即可

3、修改系统启动级别为3（文本模式）

vi /etc/inittab
...............................
id:3:initdefault:
...............................

4、精简系统自启动服务

一般自启动启动最少需要保留5个服务

分别为：sshd　　rsyslog　　network　　crontab　　sysstat

#####命令关闭其余服务###########
chkconfig --list|grep 3:on|grep -vE "crond|network|sshd|rsyslog|sysstat"|awk '{print "chkconfig "  $1 " off"}' | bash

5、给历史记录加时间显示

echo 'export HISTTIMEFORMAT="%F %T `whoami` "' >> /etc/profile

6、linux服务器内核参数优化

cat >>/etc/sysctl.conf<< OK
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.ipv4.ip_conntrack_max = 65536
net.ipv4.netfilter.ip_conntrack_max=65536
net.ipv4.netfilter.ip_conntrack_tcp_timeout_established=180
net.core.somaxconn = 16384
net.core.netdev_max_backlog = 16384
vm.swappiness=10
OK

7、linux服务器打开文件数优化

cat >>/etc/security/limits.conf<< ok 

*               soft nofile          65535
*               soft nproc           65535
*                hard nofile         65535
*                hard nproc          65535
ok

cat >>/etc/security/limits.d/90-nofile.conf<< ok
* soft nofile 65535
* hard nofile 65535
root soft nofile unlimited
ok