由于自己经常用虚拟机来做各种测试，每次创建虚拟机都要重新把该关闭的服务（比如SELinux，postfix等），每次都要重新修改主机名等等，虽然可以打快照并进行虚拟盘克隆，但是磁盘文件太大也不是我所乐见的，所以仿照网上的做法，也弄了一个shell脚本来优化一下系统，这样的话每次刷一下脚本也确实省却了不少繁琐的步骤，还算可以吧。
其实生产环境中，也可以使用这种方法，比如使用cobbler来批量安装操作系统，在安装完操作系统之后直接刷系统优化脚本，也能实现最大限度的自动化安装系统。当然有人也会说使用cobbler安装系统可以在kickstart脚本中添加优化代码，在系统安装完之后执行这些脚本，也能实现系统优化自动完成。方法很多，只要能达到目的就行，具体怎么操作看情况而定。
#!/bin/bash
#############################################
#The script is used to optimize the CentOS 6.x.
#created by Jerry12356 on May 16th, 2016
#############################################
iptables_stop(){
#关闭iptables服务，生产环境不建议这么做
/etc/init.d/iptables stop > /dev/null 2>&1
if [ $? -eq 0 ];then
echo -e "\033[1;32mStop iptables successful.\033[0m"
fi
}
selinux_disable(){
#禁用SElinux
setenforce 0 > /dev/null 2>&1
sed -i '/SELINUX/s/enforcing/disabled/' /etc/selinux/config
echo -e "\033[1;32mDisable selinux successful.\033[0m"
}
addusers(){
#添加普通用户，并设置sudo权限（不建议使用admin作为用户名）
useradd -u 603 -g users admin
echo 'admin:123456'|chpasswd
sed -i '/^root/aadmin ALL=(ALL) ALL ' /etc/sudoers
#以下为服务用户，如有相关服务，可以一并添加
useradd -u 602 -M nginx -s /sbin/nologin
useradd -u 605 -M zabbix -s /sbin/nologin
echo -e "\033[1;32mAdd users successful.\033[0m"
}
yum_install(){
#安装开发组件、运行库
yum -y install gcc gcc-c++ openssh-clients wget make cmake curl finger nmap tcp_wrappers expect lrzsz unzip zip xz ntpdate lsof telnet vim tree > /dev/null 2>&1
if [ $? -eq 0 ];then
echo -e "\033[1;32mInstall softwares successful.\033[0m"
fi
}
yum_update(){
#更新yum源
if [ ! -e "/etc/yum.repos.d/bak" ];then
mkdir /etc/yum.repos.d/bak
fi
cd /etc/yum.repos.d/
for i in `ls *.*`;do mv $i bak/$i.bak;done
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo -O /etc/yum.repos.d/CentOS-Base.repo > /dev/null 2>&1
yum clean all > /dev/null 2>&1
yum makecache > /dev/null 2>&1
echo -e "\033[1;32mUpdate repos successful.\033[0m"
}
time_sync(){
#设置时区并同步系统时间
cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
#time sync
echo -e "0 * * * * /usr/sbin/ntpdate 210.72.145.44 64.147.116.229 time.nist.gov" >> /var/spool/cron/root
echo -e "/usr/sbin/ntpdate time.nist.gov 210.72.145.44 64.147.116.229" >> /etc/rc.local
echo -e "\033[1;32mTime sync successful.\033[0m"
}
service_optimize(){
#测试环境中
for i in `chkconfig --list|grep 3:on|awk '{print $1}'`;do chkconfig --level 3 $i off;done
for i in crond network rsyslog sshd;do chkconfig --level 3 $i on;done
#生产环境中
#for service in kdump postfix lvm2-monitor messagebus iptables ip6tables ;do chkconfig $service off ;done
echo -e "\033[1;32mServices optimizd successful.\033[0m"
}
history_setting(){
#设置history历史记录
sed -i "/mv/aalias vi='vim'" /root/.bashrc
sed -i "/HISTSIZE/s/1000/10000/g" /etc/profile
echo -e 'export HISTTIMEFORMAT="`whoami` : %F %T :"' >> /etc/profile
source /etc/profile
echo -e "\033[1;32mSetting history successful.\033[0m"
}
kernel_optimize(){
echo -e "* soft nofile 2097152\n* hard nofile 2097152\n* soft nproc 2097152\n* hard nproc 2097152\n" >> /etc/security/limits.conf
echo -e "* soft nproc 10240\n" > /etc/security/limits.d/90-nproc.conf
echo -e "fs.file-max = 2097152\nfs.nr_open = 2097152\nnet.ipv4.tcp_syncookies = 1\nnet.ipv4.tcp_tw_reuse = 1\nnet.ipv4.tcp_tw_recycle = 1\nnet.ipv4.tcp_fin_timeout = 30\nnet.ipv4.tcp_keepalive_time = 1200\nnet.ipv4.ip_local_port_range = 1024 65000\nnet.ipv4.tcp_max_syn_backlog = 81920" >> /etc/sysctl.conf
sed -i '/bridge/s/^/\#/' /etc/sysctl.conf
echo -e "session required pam_limits.so" >> /etc/pam.d/login
sed -i 's/1024/100000/g' /etc/security/limits.d/90-nproc.conf
echo -e "\033[1;32mKernel optimized successful.\033[0m"
}
hostname_change(){
read -p "Input a new hostname: " HostName
sed -i "/HOSTNAME/s/localhost.localdomain/$HostName/" /etc/sysconfig/network
hostname $HostName
echo "`ifconfig eth0|grep "inet addr"|awk '{print $2}'|cut -d":" -f2` $HostName">>/etc/hosts
echo -e "\033[1;32mChange hostname successful.\033[0m"
}
iptables_stop
selinux_disable
addusers
yum_install
yum_update
time_sync
service_optimize
history_setting
kernel_optimize
hostname_change
echo -e "\033[1;32m\nAll of the operations were done, please reboot to make them took effect.\033[0m"
