安装keepalived
wget http://www.keepalived.org/software/keepalived-1.2.7.tar.gztar zxvf nginx-1.2.7.tar.gzcd nginx-1.2.7./configure --with-http_stub_status_modulemake && make install
-------------------------注意：在执行./configure --with-http_stub_status_module的时候报错因为少一个库keepalived执行./configure --prefix=/usr/local/keepalived时报错：configure: error: Popt libraries is required
出现此错误的原因：
未安装popt的开发包
解决方法：
yum install popt-devel
安装好popt的开发包。
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运行环境
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
mkdir /etc/keepalivedcp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
加入启动服务
echo "/etc/init.d/keepalived start" >> /etc/rc.local---------------------------------------------------
Keepalived 加载的脚本
keepalived -help中
keepalived --use-file -f Use the specified configuration file.
Default is /etc/keepalived/keepalived.conf
默认使用的是 /etc/keepalived/keepalived.conf配置文件
配置keepalived
按照上面的安装方法，keepalived的配置文件在/etc/keepalived/keepalived.conf。主、从服务器的配置相关联但有所不同。如下：
Master:
global_defs { router_id nginx_master}
vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 50.1.1.2 }}
Backup:
global_defs {notification_email { router_id nginx_backup}
vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 51 priority 99 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 50.1.1.2 }}
验证： 先后在主、从服务器上启动keepalived: /etc/init.d/keepalived start 在主服务器上查看是否已经绑定了虚拟IP： ip addr 停止主服务器上的keepalived: /etc/init.d/keepalived stop 然后在从服务器上查看是否已经绑定了虚拟IP： 启动主服务器上的keepalived，看看主服务器能否重新接管虚拟IP
让keepalived监控NginX的状态 经过前面的配置，如果主服务器的keepalived停止服务，从服务器会自动接管VIP对外服务；一旦主服务器的keepalived恢复，会重新接管VIP。 但这并不是我们需要的，我们需要的是当NginX停止服务的时候能够自动切换。 keepalived支持配置监控脚本，我们可以通过脚本监控NginX的状态，如果状态不正常则进行一系列的操作，最终仍不能恢复NginX则杀掉keepalived，使得从服务器能够接管服务。
如何监控NginX的状态 最简单的做法是监控NginX进程，更靠谱的做法是检查NginX端口，最靠谱的做法是检查多个url能否获取到页面。
如何尝试恢复服务 如果发现NginX不正常，重启之。等待3秒再次校验，仍然失败则不再尝试。根据上述策略很容易写出监控脚本。这里使用nmap检查nginx端口来判断nginx的状态，记得要首先安装nmap。监控脚本如下:#!/bin/sh# check nginx server statusNGINX=/usr/local/nginx/sbin/nginxPORT=80
nmap localhost -p $PORT | grep "$PORT/tcp open"#echo $?if [ $? -ne 0 ];then $NGINX -s stop $NGINX sleep 3 nmap localhost -p $PORT | grep "$PORT/tcp open" [ $? -ne 0 ] && /etc/init.d/keepalived stopfi
不要忘了设置脚本的执行权限，否则不起作用。假设上述脚本放在/opt/chk_nginx.sh，则keepalived.conf中增加如下配置：
vrrp_script chk_http_port { script "/opt/chk_nginx.sh" interval 2 weight 2}track_script { chk_http_port}
这里又遇到了问题就是脚本怎么都不执行：最后找到解决办法:将 track_script 嵌入到 vrrp_instance 里面
如下：
global_defs {
router_id nginx_master
}
vrrp_script chk_http_port
{
script "/opt/chk_nginx.sh"
interval 1
weight -2
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 101
advert_int 1
track_script {
chk_http_port
}
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.16.1.111
}
}