@(终于等到你)

安装前准备

基础系统：CentOS 7

yum -y install gcc gcc-c++ autoconf automake make 
yum -y install zlib zlib-devel openssl openssl-devel pcre pcre-devel

1.下载keepalived

方法一：

yum -y install keepalived

方法二：
下载二进制源码包：http://www.keepalived.org/download.html

#下载安装文件

cd /usr/local
wget http://www.keepalived.org/software/keepalived-2.0.18.tar.gz
#解压文件
tar -zxvf keepalived-2.0.18.tar.gz
#编译
cd keepalived-2.0.18/
#--prefix 指定安装地址
#/usr/local/keepalived/ 安装的目录，不要和自己安装文件一个目录，不然报错
./configure --prefix=/usr/local/keepalived/
#编译并安装
 make && make install

2.配置

复制文件：

[[email?protected] ~]# cp /usr/local/keepalived-2.0.18/keepalived/etc/init.d/keepalived /etc/init.d/
[[email?protected] ~]# mkdir /etc/keepalived
[[email?protected] ~]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
[[email?protected] ~]# cp /usr/local/keepalived-2.0.18/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
[[email?protected] ~]# cp /usr/local/keepalived/sbin/keepalived /usr/sbin/

编辑：

vi /etc/keepalived/keepalived.conf

/etc/keepalived/keepalived.conf内容如下

global_defs {
    notification_email {
        #[email?protected]       # 指定keepalived在发生切换时需要发送email到的对象，一行一个
        #[email?protected]
    }
    notification_email_from [email?protected]   # 指定发件人
    smtp_server [email?protected]              # smtp 服务器地址
    smtp_connect_timeout 30               # smtp 服务器连接超时时间
    router_id LVS_1 # 必填，标识本节点的字符串,通常为hostname,但不一定非得是hostname,故障发生时,邮件通知会用到
    }

vrrp_script chk_tomcat {                    #详细看下面
    script "/etc/keepalived/tomcat_check.sh"            #检测服务shell
    interval 2                                  #每个多长时间探测一次
    weight -20                                          #每个多长时间探测一次                                             
}

_instance VI_1 {  # 实例名称
    state MASTER      #  必填，可以是MASTER或BACKUP，不过当其他节点keepalived启动时会将priority比较大的节点选举为MASTER
    interface ens33    #  必填， 节点固有IP（非VIP）的网卡，用来发VRRP包做心跳检测
    mcast_src_ip 192.168.2.89 #本机的ip，需要修改
    virtual_router_id 101 #  必填，虚拟路由ID,取值在0-255之间,用来区分多个instance的VRRP组播,同一网段内ID不能重复;主备必须为一样;
    priority 100      #  必填，用来选举master的,要成为master那么这个选项的值最好高于其他机器50个点,该项取值范围是1-255(在此范围之外会被识别成默认值100)
    advert_int 1      #  必填，检查间隔默认为1秒,即1秒进行一次master选举(可以认为是健康查检时间间隔)
    authentication {  #  必填，认证区域,认证类型有PASS和HA（IPSEC）,推荐使用PASS(密码只识别前8位)
        auth_type PASS  # 默认是PASS认证
        auth_pass 1111 # PASS认证密码
    }
    virtual_ipaddress {
        192.168.2.90    #  必填，虚拟VIP地址,允许多个
    }
    track_script {       # 检测shell                          
        chk_tomcat
    }
}

vrrp_script 里的script返回值为0时认为检测成功，其它值都会当成检测失败；

1. weight 为正时，脚本检测成功时此weight会加到priority上，检测失败时不加；
   A.主失败：主 priority < 从 priority + weight 时会切换。
   B.主成功：主 priority + weight > 从 priority + weight 时，主依然为主
2. weight 为负时，脚本检测成功时此weight不影响priority，检测失败时priority – abs(weight)
   A.主失败：主 priority – abs(weight) < 从priority 时会切换主从
   主成功：主 priority > 从priority 主依然为主

检测shell：/etc/keepalived/tomcat_check.sh 可以根据 tomcat 服务检测结果返回不同的值，成功执行 exit 0 返回 0，失败执行 exit 1 返回 1，vrrp_script 可以结合返回值来对当前keepalived优先级做处理

3.开启服务

设置 keepalived 服务开机启动

# chkconfig keepalived on  
# 启动keepalived 服务
# service keepalived start

查看keepalived进程，出现如下三个进程即为启动成功

[[email?protected] ~]# ps -ef | grep keep
root       7925      1  0 11:27 ?        00:00:00 /usr/local/keepalived/sbin/keepalived -D
root       7926      1  0 11:27 ?        00:00:00 /usr/local/keepalived/sbin/keepalived -D
root       7927   7926  0 11:27 ?        00:00:00 /usr/local/keepalived/sbin/keepalived -D
root       7956   7888  0 12:02 pts/1    00:00:00 grep --color=auto keep

4.指定日志的输出文件

修改 /etc/sysconfig

vim  /etc/sysconfig
#指定位置修改为如下内容
KEEPALIVED_OPTIONS="-D -d -S 0"

修改 /etc/rsyslog.conf

vim /etc/rsyslog.conf
#在最后一行添加如下内容
local0.* /var/log/keepalived.log

重启服务测试

service rsyslog restart
service rsyslog restart

#如下命令有日志内容输出即为成功
tailf /var/log/keepalived.log

#centos 基本可以成功，但是 debain 可能失败，失败上面 2 个文件可以改为如下内容，再重启服务测试
KEEPALIVED_OPTIONS="-D -d -S 1"
local1.* /var/log/keepalived.log

参考：https://blog.csdn.net/weixin_33845881/article/details/86016142

如果有哪些不对的地方烦请指认，先行感谢