nginx1 ip:192.168.12.4 #MASTER
nginx2 ip:192.168.12.10 #BACKUP
nginx_vip :192.168.12.100

原理可参考：
http://www.keepalived.org/documentation.html
系统为CentOS7

1、配置一下yum源

curl -L http://mirrors.aliyun.com/repo/Centos-7.repo > /etc/yum.repos.d/CentOS-Base.repo
curl -L http://mirrors.aliyun.com/repo/epel-7.repo > /etc/yum.repos.d/epel.repo

yum -y install keepalived nginx

2、设置服务器基本环境

关闭防火墙:iptables -F;service iptables save
关闭seLinux:setenforce 0;sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux

3、配置一下nginx,好区分测试环境

192.168.12.4:
echo 192.168.12.4 > /usr/share/nginx/html/index.html

192.168.12.10:
echo 192.168.12.10 > /usr/share/nginx/html/index.html

4、配置keepalived.conf

[root@192.168.12.4]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
notification@mail.com
}
notification_email_from fromnotification@mail.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}

vrrp_script check_nginx {
script "sh /etc/keepalived/check_nginx.sh"
interval 2
}

vrrp_instance VI_1 {
state MASTER
interface eth0
mcast_src_ip 192.168.12.4
virtual_router_id 51
priority 100
advert_int 2
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.12.100
}
track_script {
check_nginx
}
}

[root@192.168.12.10]# cat keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
notification@mail.com
}
notification_email_from fromnotification@mail.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}

vrrp_script check_nginx {
script "sh /etc/keepalived/check_nginx.sh"
interval 2
}

vrrp_instance VI_1 {
state BACKUP
interface eth0
mcast_src_ip 192.168.12.10
virtual_router_id 51
priority 99
advert_int 2
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.12.100
}
track_script {
check_nginx
}
}

脚本check_nginx.sh内容如下

#!/bin/bash

A=`pgrep nginx|wc -l`
if [ $A -eq 0 ];then
/bin/systemctl start nginx.service
if [ `pgrep nginx|wc -l` -eq 0 ];then
/bin/systemctl stop keepalived.service
fi
fi

5、启动
在两个服务器执行启动命令
service nginx start
service keepalived start

6、检查

[root@192.168.12.4 keepalived]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:85:83:e8 brd ff:ff:ff:ff:ff:ff
inet 192.168.12.4/24 brd 192.168.12.255 scope global eth0
valid_lft forever preferred_lft forever
inet 192.168.12.100/32 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe85:83e8/64 scope link
valid_lft forever preferred_lft forever

[root@192.168.12.10 keepalived]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:62:6a:50 brd ff:ff:ff:ff:ff:ff
inet 192.168.12.10/24 brd 192.168.12.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe62:6a50/64 scope link
valid_lft forever preferred_lft forever

仔细观察可以发现192.168.12.4的服务器多了一个IP，就是192.168.12.100，这个就是VIP
再看日志发现主服务器日志有这下面一条：
Jul 12 10:30:57 localhost Keepalived_vrrp[2510]: VRRP_Instance(VI_1) Entering MASTER STATE

备服务器日志
Jul 11 00:01:00 localhost Keepalived_vrrp[111937]: VRRP_Instance(VI_1) Entering BACKUP STATE

综上主备已搭建成功

7、模拟主nginx宕机：