给出的虚拟IP为10.0.0.110

1. 给出MASTER的配置文件：

   ! Configuration File for keepalived
   #这里给出keepalived -v的版本信息  
   #Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2
   global_defs {
       router_id nginx_load_balance_01
       enable_script_security on
       script_user keepalived_script
       #不对，原因未知
       #default_interface ens33
   }
   #注意，这里一定要给成双引号，单引号不行
   #好的策略是BACKUP的priority不变
   #MASTER OK的话，优先级不变
   #MASTER ERR的话，优先级减小
   #再联系下面的check_nginx脚本
   #推出weight为负数
   vrrp_script check_nginx {
       script "/home/keepalived_script/check_nginx"
       weight -7
   }
   
   vrrp_instance nginx_load_balance {
       state MASTER
       interface ens33
       virtual_router_id 51
       priority 10
       advert_int 1
       #nopreempt好像得配置在backup机器上
       #nopreempt 
       authentication {
           auth_type PASS
           auth_pass 111111
       }
       #不好使__start__
       #指定要track哪些网卡，一旦这些网卡down了，那么，这个vrrp_instance就进入fault状态
       #track_interface {
       #   ens33
       #   ens34
       #}
       #不好使__end__
       #因为只是在网络层面track网卡是不够的，我们还要进行监控某些应用层的东西
       track_script {
           check_nginx
       }
       #注意，这里一定要给成双引号，单引号不行
       notify_master "/home/keepalived_script/change_to_master"
       notify_backup "/home/keepalived_script/change_to_backup"
       notify_fault  "/home/keepalived_script/change_to_fault"
       virtual_ipaddress {
           10.0.0.110/8
       }
   
   }
   

2. 然后是/home/keepalived_script/check_nginx脚本：

   #!/bin/env sh
   ret=$(ss -tunlp | grep 80 | wc -l)
   if [ $ret -lt 1 ]; then
       exit 1
   else 
       exit 0
   fi
   

3. 然后是BACKUP的配置：

   ! Configuration File for keepalived
   #这里给出keepalived -v的版本信息 
   #Keepalived v1.3.5 (03/19,2017), git commit v1.3.5-6-g6fa32f2
   global_defs {
       router_id nginx_load_balance_02
       enable_script_security on
       script_user keepalived_script
   }
   #注意，这里一定要使用双引号
   #vrrp_script check_nginx {
   #  script "/home/keepalived_script/check_nginx"
   #  weight -7
   #}
   vrrp_instance nginx_load_balance {
       state BACKUP
       interface ens33
       virtual_router_id 51
       priority 5
       advert_int 1
       #这个不能打开。这个选项的意思是当MASTER down了以后，
       #BACKUP不抢占虚拟IP。
       #启动时，日志输出中有Preempt disabled
       #nopreempt on
       authentication {
           auth_type PASS
           auth_pass 111111
       }
       #不好使__start__
       #指定要track哪些网卡，一旦这些网卡down了，那么，这个vrrp_instance就进入fault状态
       #track_interface {
       #    ens33
       #    ens34
       #}   
       #不好使__end__
       #注意，这里一定要给成双引号，单引号不行
       notify_master "/home/keepalived_script/change_to_master"
       notify_backup "/home/keepalived_script/change_to_backup"
       notify_fault  "/home/keepalived_script/change_to_fault"
       #因为只是在网络层面track网卡是不够的，我们还要进行监控某些应用层的东西
       #track_script {
       #    check_nginx
       #}   
       virtual_ipaddress {
           10.0.0.110/8
       }   
   }
   
   

1. 遗留问题：
   1. global_defs中的default_interface什么意思，会在哪个模块中用到，VRRP，LVS还是SNMP？
   2. 启动时，日志文件（/var/log/messages）中会有这么一个报错：“PID file /var/run/keepalived.pid not readable (yet?) after start.”，这是为什么？这里给出/usr/lib/systemd/system/keepalived.service中的配置信息：

      
      [Unit]
      Description=LVS and VRRP High Availability Monitor
      After=syslog.target network-online.target
      
      [Service]
      Type=forking
      PIDFile=/var/run/keepalived.pid
      KillMode=process
      EnvironmentFile=-/etc/sysconfig/keepalived
      ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS
      ExecReload=/bin/kill -HUP $MAINPID
      
      [Install]
      WantedBy=multi-user.target