干货！超实用的 Linux 初始化脚本！

• 定义相关变量

#环境变量
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
export PATH

#当前时间
current_time=$(date +%Y%m%d)

#阿里的DNS
dns_server=223.5.5.5 

• 配置 yum 镜像源

if [[ ! -z `uname -r|grep 'el6'` ]]
    then
    kernel_version=el6
    yum_repo=http://mirrors.aliyun.com/repo/Centos-6.repo
elif [[ ! -z `uname -r|grep 'el7'` ]]
    then
    kernel_version=el7
    yum_repo=http://mirrors.aliyun.com/repo/Centos-7.repo
else
    echo -e "\e[31mUnidentified Kernel version: $(uname -r). Only support for kernel el6/el7\e[0m"
    exit
fi

• 获取阿里云 yum 镜像源

function add_yum_repo(){
    local item="Add Aliyun Yum Mirrors"
    yum clean all
    cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.${current_time} && \
    curl -o /etc/yum.repos.d/CentOS-Base.repo ${yum_repo} > /dev/null 2>&1
    show_result $? "${item}"
    yum makecache
}

• 判断函数是否执行成功

function show_result(){
    if [ "$1" -eq 0 ]
        then
            echo -e "\e[32m$2 is Success .   [ OK ] \e[0m"
        else
            echo -e "\e[31m$2 is Fail .   [ FAIL ] \e[0m"
    fi
}

• 写入一行配置

function add_newconfig(){
    local SearchResult=`grep "$1" "$2"`
    if [ -z "${SearchResult}" ]
        then
        echo "$1" >> $2
    fi
}

• 修改配置

function add_config(){
    local keywords=`echo $1| awk -F "[= ]+" '{print $1}'`
    local SearchResult=`grep "^${keywords}" "$2"`
    if [ -z "${SearchResult}" ] #空为真，非空为假
        then
        echo $1 >> $2
    else
        sed -i "s/^${keywords}.*/$1/" $2
    fi
}

• 配置系统时区

function config_localtime(){
    local item="Config SH As Location"
    rm -f /etc/localtime
    ln -s  /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
    show_result $? "${item}"
}

• 配置 dns 服务器

function config_dns_addr(){
    local item="Config DNS Address"
    cp /etc/resolv.conf /etc/resolv.conf.${current_time} && \
    echo "nameserver ${dns_server}" > /etc/resolv.conf
    show_result $? "${item}"
}

• 修改最大文件描述符限制

function maximum_file_dspt(){
    local item="Maximum File Descriptor"
    cp /etc/security/limits.conf /etc/security/limits.conf.${current_time} && \
    echo "*           soft    nofile          100000
*           hard    nofile          100000
*           soft    nproc           65535
*           hard    nproc           65535
*           soft    core            unlimited
*           hard    core            unlimited" > /etc/security/limits.conf
    show_result $? "${item}"
}

• 关闭系统不需要的服务

function shutdown_nonuse_srv(){
    local item="Shutdown Unused Services"
    if [[ "${kernel_version}" == el6 ]]
            then
        for i in `chkconfig --list | awk '{print $1}'`
            do
            chkconfig --level 2345 $i off > /dev/null 2>&1
            done
        for ii in crond network rsyslog sshd sysstat haldaemon
            do
            chkconfig --level 2345 $ii on > /dev/null 2>&1
            done
        show_result $? "${item}"
    elif [[ "${kernel_version}" == el7 ]]
        then
        systemctl disable postfix > /dev/null 2>&1
        show_result $? "${item}"
    else
        echo -e "\e[31mUnidentified Kernel version: $(uname -r). Only support for kernel el6/el7\e[0m"
    fi
}

• 内核参数优化相关

function optimize_kel_args(){
    local item="Optimize Kernel Arguments"
    cp /etc/sysctl.conf /etc/sysctl.conf.${current_time} > /dev/null 2>&1
    arch_ratio=$([[ ! -z $(uname -a | grep x86_64) ]] && expr 64 / 32 || expr 32 / 32)
    memory_size=$(free -b| awk 'NR==2{print $2}')
    nf_conntrack_size=$(expr ${memory_size} / 16384 / ${arch_ratio})
    #开启反向路径过滤
    add_config "net.ipv4.conf.default.rp_filter = 1" /etc/sysctl.conf
    add_config "net.ipv4.conf.all.rp_filter = 1" /etc/sysctl.conf
    #处理无源路由包
    add_config "net.ipv4.conf.all.accept_source_route = 0" /etc/sysctl.conf
    add_config "net.ipv4.conf.default.accept_source_route = 0" /etc/sysctl.conf
    #core文件名中添加pid作为扩展名
    add_config "kernel.core_uses_pid = 1" /etc/sysctl.conf
    #开启syn洪水攻击保护
    add_config "net.ipv4.tcp_syncookies = 1" /etc/sysctl.conf
    #修改消息队列长度
    add_config "kernel.msgmnb = 65536" /etc/sysctl.conf
    add_config "kernel.msgmax = 65536" /etc/sysctl.conf
    #修改最大内存共享段大小bytes
    add_config "kernel.shmmax = 68719476736" /etc/sysctl.conf
    add_config "kernel.shmall = 4294967296" /etc/sysctl.conf
    #timewait数量默认18000
    add_config "net.ipv4.tcp_max_tw_buckets = 600" /etc/sysctl.conf
    add_config "net.ipv4.tcp_sack = 1" /etc/sysctl.conf
    add_config "net.ipv4.tcp_window_scaling = 1" /etc/sysctl.conf
    add_config "net.ipv4.tcp_rmem = 4096 87380 16777216" /etc/sysctl.conf
    add_config "net.ipv4.tcp_wmem = 4096 65536 16777216" /etc/sysctl.conf
    add_config "net.core.rmem_default = 8388608" /etc/sysctl.conf
    add_config "net.core.wmem_max = 16777216" /etc/sysctl.conf
    #未收到客户端确认信息连接请求的最大值
    add_config "net.ipv4.tcp_max_syn_backlog = 262144" /etc/sysctl.conf
    #放弃建立连接之前发送的synack包
    add_config "net.ipv4.tcp_syn_retries = 2" /etc/sysctl.conf
    #开启重用，允许time—wait socket 重新用语新的tcp连接
    add_config "net.ipv4.tcp_tw_reuse = 1" /etc/sysctl.conf
    add_config "net.ipv4.tcp_fin_timeout = 1" /etc/sysctl.conf
    #防止简单的ddos攻击
    add_config "net.ipv4.tcp_max_orphans = 3276800" /etc/sysctl.conf
    #启用timewait快速收回
    add_config "net.ipv4.tcp_tw_recycle = 0" /etc/sysctl.conf
    #keeptime启用时tcp发送keepalive消息的频度，默认2h
    add_config "net.ipv4.tcp_keepalive_time = 600" /etc/sysctl.conf
    #允许系统打开的端口范围
    add_config "net.ipv4.ip_local_port_range = 1024 65535" /etc/sysctl.conf
    #资源回收
    add_config "net.ipv4.tcp_tw_recycle = 0" /etc/sysctl.conf
    #路由转发
    add_config "net.ipv4.ip_forward = 1" /etc/sysctl.conf 
    #修改防火墙连接跟踪表大小，默认65535
    add_config "net.netfilter.nf_conntrack_max = ${nf_conntrack_size}" /etc/sysctl.conf
    add_config "net.nf_conntrack_max = ${nf_conntrack_size}" /etc/sysctl.conf
    #解禁ping
    add_config "net.ipv4.icmp_echo_ignore_all = 0" /etc/sysctl.conf
        modprobe bridge
    sysctl -p > /dev/null 2>&1
    show_result $? "${item}"
}

• 安装常用工具

function install_pkgs(){
    local item="Install Common Pkgs"
    yum -y groupinstall "Development libraries" > /dev/null 2>&1
    yum -y groupinstall "Development tools" > /dev/null 2>&1
    yum -y install sysstat  tree  lrzsz  telnet wget net-tools tcpdump lsof vim ntp > /dev/null 2>&1
    show_result $? "${item}"
}

• 关闭 SELinux

function shutdown_selinux(){
    local item="Shutdown Selinux "
    setenforce 0 > /dev/null 2>&1
    cp /etc/selinux/config /etc/selinux/config.${current_time} && \
    sed -i 's:SELINUX=enforcing:SELINUX=disabled:g' /etc/selinux/config
    show_result $? "${item}"
}

• 主函数

function main(){
    echo -e '\033[34;1m开始初始化操作系统中......\033[0m'
    add_yum_repo
    install_pkgs
    config_localtime
    config_dns_addr
    maximum_file_dspt
    shutdown_nonuse_srv
    shutdown_selinux
    optimize_kel_args
    echo -e '\033[34;1m服务器系统初始化已完成！\033[0m'
}

main