centos7系统初始化

    echo "# swappiness=0的时候表示最大限度使用物理内存，然后才是 swap空间" >> /etc/sysctl.conf
    echo -e "vm.swappiness = 0
" >> /etc/sysctl.conf
    echo "#  ARP参数，检查一次相邻层记录的有效性的周期。当相邻层记录失效" >> /etc/sysctl.conf
    echo -e "net.ipv4.neigh.default.gc_stale_time=120
" >> /etc/sysctl.conf
    echo "# 路由设定" >> /etc/sysctl.conf
    echo -e "net.ipv4.conf.all.rp_filter=0
" >> /etc/sysctl.conf
    echo "#启用源路由核查功能" >> /etc/sysctl.conf
    echo -e "net.ipv4.conf.default.rp_filter=0
" >> /etc/sysctl.conf
    echo "#限制arp 协议要发的要求，2 始终使用最好的解决这一目标" >> /etc/sysctl.conf
    echo "net.ipv4.conf.default.arp_announce = 2" >> /etc/sysctl.conf
    echo "net.ipv4.conf.lo.arp_announce=2" >> /etc/sysctl.conf
    echo -e "net.ipv4.conf.all.arp_announce=2
" >> /etc/sysctl.conf
    echo "#timewait的数量，默认是180000" >> /etc/sysctl.conf
    echo -e "net.ipv4.tcp_max_tw_buckets = 100000
" >> /etc/sysctl.conf
    echo "#开启SYN洪水攻击保护" >> /etc/sysctl.conf
    echo -e "net.ipv4.tcp_syncookies = 1
" >> /etc/sysctl.conf
    echo "#记录的那些尚未收到客户端确认信息的连接请求的最大值。对于有128M内存的系统而言，缺省值是1024，小内存的系统则是128" >> /etc/sysctl.conf
    echo -e "net.ipv4.tcp_max_syn_backlog = 1024
" >> /etc/sysctl.conf
    echo "#为了打开对端的连接，内核需要发送一个SYN并附带一个回应前面一个SYN的ACK。也就是所谓三次握手中的第二次握手。这个设置决定了内核放弃连接之前发送SYN+ACK包的数量" >> /etc/sysctl.conf
    echo -e "net.ipv4.tcp_synack_retries = 2
" >> /etc/sysctl.conf
    echo "#禁用ipv6协议" >> /etc/sysctl.conf
    echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf
    echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.conf
    echo "net.ipv6.conf.lo.disable_ipv6 = 1" >> /etc/sysctl.conf=
    echo "#脏页的老化时间，默认30秒，多久刷盘一次" >> /etc/sysctl.conf
    echo "vm.dirty_expire_centisecs = 3000" >> /etc/sysctl.conf
    echo "#pdflush多久工作一次" >> /etc/sysctl.conf
    echo "vm.dirty_writeback_centisecs = 500" >> /etc/sysctl.conf
    echo "#如果脏页到达剩余的10%，kernel 在调节，而不是pdflush" >> /etc/sysctl.conf
    echo "vm.dirty_background_ratio = 10" >> /etc/sysctl.conf
    echo "#低位内存 30秒一次（到达20%） 小数据文件，随即数较多，可以适当把这个值设置大一些，性能更好一些。" >> /etc/sysctl.conf
    echo "vm.dirty_ratio = 30 " >> /etc/sysctl.conf
    echo "#到达字节" >> /etc/sysctl.conf
    echo "vm.dirty_bytes = 0">> /etc/sysctl.conf
    echo "vm.dirty_background_bytes = 0">> /etc/sysctl.conf
    sysctl -p