1. keepalived**是什么？
      Keepalived软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：NginxHaproxy、MySQL等）的高可用解决方案软件。Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，VRRP是通过一种竞选机制来将路由的任务交给某台VRRP路由器的。它能够保证当个别节点宕机时，整个网络可以不间断地运行，所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。
      keepalived官网http://www.keepalived.org

      2**、Keepalived高可用故障切换转移原理
      Keepalived高可用服务对之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。在 Keepalived服务正常工作时，主 Master节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备Backup节点自己还活看，当主 Master节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master节点的心跳了，于是调用自身的接管程序，接管主Master节点的 IP资源及服务。而当主 Master节点恢复时，备Backup节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。
      3**、 keepalived服务的安装
       ** 3.1下载keepalived源码包并解压
      A. 联网获取KeepAlived软件安装包（官网获取）
      [root@localhost ~]# wget http://www.keepalived.org/software/keepalived-1.2.15.tar.gz
      B. 解压安装包至指定的安装目录
      [root@localhost ~]# tar zxvf keepalived-1.2.15.tar.gz -C /usr/local/src
      ** 3.2编译安装keepalived
       A**．进入至KeepAlived目录下
      [root@localhost ~]# cd /usr/local/src/keepalived-1.2.15/
      B．配置KeepAlived
      [root@localhost ~]# ./configure —prefix=/usr/local/keepalived —sbindir=/usr/local/keepalived/sbin
      C．编译KeepAlived
      [root@localhost ~]# make && make install
      **3.3对keepalived进行相关优化
      将keepalived启动命令添加至系统全局启动，如此可以避免进入KeepAlived安装目录启动。      如下俩个命令缺一不可！
       ** A． 创建keepalived配置文件目录
      [root@localhost ~]# mkdir -p /etc/keepalived
      **B． 拷贝keepalived配置文件至/etc/keepalived
      [root@localhost keepalived]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived
       C．拷贝KeepAlived启动命令至对应的/sbin目录下
      [root@localhost keepalived]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
       D．拷贝KeepAlived的配置文件至/etc/sysconfig目录下
      [root@localhost keepalived]# cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
       E.将keepalived启动脚本添加到系统服务
      [root@localhost keepalived]# cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
       F．添加KeepAlived启动优先级并启用
      [root@localhost keepalived]# chkconfig —add keepalived
      [root@localhost keepalived]# chkconfig —level 2345 keepalived on
       备注说明：
      1）. keepalived安装完成后，安装目录为:/usr/lccal/keepalived, 配置文件路径为:/etc/keepalive/;
      2.） 安装完成后，需要将启动脚本复制到/etc/ini.d/下;
      3.） 注意一定要执行述上的相关操作，不然有可能导致keepalived服务起不来;
      3.4服务启动和进程查看**

    • 启动命令

      1.    [root@localhost ~]# service keepalived start

    • 状态 查询命令

         [root@localhost ~]# service keepalived status

    • n 进程查询命令

         [root@localhost ~]# ps aux | grep keepalived

    • n 停止命令

         [root@localhost ~]# service keepalived stop