这里我们仅仅只利用Keepalive做双机热备，也就是保证服务器的高可用性，其他的不用管。可能您会说这样在实际应用中很少会这样用，这您可就错了，Keepalived仅仅做双机热备的情况还是有的，我就碰到过几次这样的案例，下面就我碰到的几个案例做个小结一，Keepalived双机热备的应用场景1，网站流量不高，压力不大，但是对服务器的可靠性要求极其高，例如实时在线OA系统，政府部门网站系统，医院实时报医系统，公安局在线报案系统，股市后台网站系统等等，他们的压力不是很大，但是对可靠性要求是非常高的2，有钱没地方花的，典型的政府企业，公办学校等等二，Keepalived双机热备的特性以及优缺点特性：1，至少需要两台服务器，其中一台为master始终提供服务，另外一台作为backup始终处于空闲状态，只有在主服务器挂掉的时候他就来帮忙了，这是典型的双击热备2，能根据需求判断服务是否可用，在不可用的时候要即使切换优缺点：优点：数据同步非常简单，不像负载均衡对数据一致性要求非常高，实现起来相对复杂维护也颇为不便，双机热备用rsync就可以实现了操作和维护非常简单缺点：服务器有点浪费，始终有一台处于空闲状态三，Keepalived双机热备的配置首先画个双机热备拓扑图吧：

这里我只写最终实现的配置，至于Keepalived的理论知识请参考《》1，本例通过Keepalived来实现两台LNMP(也就是linux+nginx+mysql+php)架构服务器的双机热备LNMP的配置请参考：《》2，Keepalived配置双机安装配置1》Keepalived安装keepalived官方地址：，大家可以到这里下载最新版本的keepalived操作系统：centos 5.5 32bit系统安装：最小化安装，也就是去掉所有组件环境配置：安装make 和 gcc openssl openssl-devel等等

1. yum -y install gcc make openssl openssl-devel wget kernel-devel

2. mkdir -p /usr/local/src/hasoft

3. cd /usr/local/src/hasoft

4. wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz

5. tar -zxvf keepalived-1.2.2.tar.gz

6. cd keepalived-1.2.2

7. ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/

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预编译后出现：

1. Keepalived configuration

2. ------------------------

3. Keepalived version       : 1.2.2

4. Compiler                 : gcc

5. Compiler flags           : -g -O2 -DETHERTYPE_IPV6=0x86dd

6. Extra Lib                : -lpopt -lssl -lcrypto

7. Use IPVS Framework       : Yes

8. IPVS sync daemon support : Yes

9. IPVS use libnl           : No

10. Use VRRP Framework       : Yes

11. Use Debug flags          : No

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1. make && make install

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这里注意哦，我上面是指通用的安装方法，如果你没有用到LVS可以把lvs去掉即

./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/ --disable-lvs-syncd --disable-lvs但这个没有影响，就按照我的来配置吧，不过如果你要是集成了LVS，那么就不可加这两个参数了哦整理管理文件：cp /usr/local/keepalived/sbin/keepalived /usr/sbin/cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/

建立配置文件目录(注意：keepalived的配置文件默认在/etc/keepalived/目录)mkdir -p /etc/etc/keepalived/两台服务器(两个节点)都这样安装即可2》配置节点A配置如下：vi /etc/keepalived/keepalived.conf

1. global_defs

2. {

3. notification_email

4. {

5. admin@example.com

6. admin@ywlm.net

7. }

8. notification_email_from admin@example.com

9. smtp_server 127.0.0.1

10. stmp_connect_timeout 30

11. router_id lnmp_node1

12. }

14. vrrp_instance lnmp {

15. state MASTER

16. interface eth0

17. virtual_router_id 100

18. priority 200

19. advert_int 5

20. track_interface {

21. eth0

22. eth1

23. }

24. authentication {

25. auth_type PASS

26. auth_pass 123456

27. }

28. virtual_ipaddress {

29. 192.168.17.200

30. }

31. }

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节点B配置如下：vi /etc/keepalived/keepalived.conf

1. global_defs

2. {

3. notification_email

4. {

5. admin@example.com

6. admin@ywlm.net

7. }

8. notification_email_from admin@example.com

9. smtp_server 127.0.0.1

10. stmp_connect_timeout 30

11. router_id lnmp_node1

12. }

14. vrrp_instance lnmp {

15. state MASTER

16. interface eth0

17. virtual_router_id 100

18. priority 150

19. advert_int 5

20. track_interface {

21. eth0

22. eth1

23. }

24. authentication {

25. auth_type PASS

26. auth_pass 123456

27. }

28. virtual_ipaddress {

29. 192.168.17.200

30. }

31. }

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四，启动调试

在节点A上启动/usr/local/keepalived/sbin/keepalived启动日志：Sep  8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink reflectorSep  8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink command channelSep  8 18:26:02 centosa Keepalived_vrrp: Registering gratutious ARP shared channelSep  8 18:26:02 centosa Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.Sep  8 18:26:02 centosa Keepalived_vrrp: Configuration is using : 36076 BytesSep  8 18:26:02 centosa Keepalived_vrrp: Using LinkWatch kernel netlink reflector...Sep  8 18:26:02 centosa Keepalived: Starting VRRP child process, pid=5606Sep  8 18:26:07 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATESep  8 18:26:12 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATESep  8 18:26:12 centosa avahi-daemon[2528]: Registering new address record for 192.168.17.200 on eth0.在节点B上启动/usr/local/keepalived/sbin/keepalived开机自动启动echo /usr/local/keepalived/sbin/keepalived >> /etc/rc.local启动日志：Sep  8 18:30:02 centosb Keepalived: Starting Keepalived v1.2.2 (09/08,2011)Sep  8 18:30:02 centosb Keepalived: Starting Healthcheck child process, pid=5837Sep  8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink reflectorSep  8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink command channelSep  8 18:30:02 centosb Keepalived_vrrp: Registering gratutious ARP shared channelSep  8 18:30:02 centosb Keepalived: Starting VRRP child process, pid=5839Sep  8 18:30:02 centosb kernel: IPVS: Registered protocols (TCP, UDP, AH, ESP)Sep  8 18:30:02 centosb kernel: IPVS: Connection hash table configured (size=4096, memory=32Kbytes)Sep  8 18:30:02 centosb kernel: IPVS: ipvs loaded.Sep  8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink reflectorSep  8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink command channelSep  8 18:30:02 centosb Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.Sep  8 18:30:02 centosb Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.Sep  8 18:30:02 centosb Keepalived_vrrp: Configuration is using : 36252 BytesSep  8 18:30:02 centosb Keepalived_vrrp: Using LinkWatch kernel netlink reflector...Sep  8 18:30:02 centosb Keepalived_healthcheckers: Configuration is using : 6271 BytesSep  8 18:30:02 centosb Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...Sep  8 18:30:02 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATE从日志可以看出，启动都没有问题，并且安装我给的优先级完成了竞选，各自成就了各自的状态关闭节点A的网卡测试切换是否正常ifdown eth0观察节点B的日志：Sep  8 18:32:55 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATESep  8 18:33:00 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATESep  8 18:33:00 centosb avahi-daemon[2531]: Registering new address record for 192.168.17.200 on eth0.启动节点A的网卡测试切换是否正常ifup eth0观察节点B的日志：Sep  8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Received higher prio advertSep  8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATESep  8 18:33:31 centosb avahi-daemon[2531]: Withdrawing address record for 192.168.17.200 on eth0.Received higher prio advert：表示接收到更高优先级的公告(advert公告的意思)Withdrawing：撤回的意思，可以看出切换过程一目了然OK，到这里我们的安装部分完成，下面我们来看看如何监控服务吧，我们这里仅仅是监控了网络故障和keepalived本身进程，在网络或者 keepalived进程出现问题的时候会切换，但是我的节点A里面还有很多服务呢，例如nginx，PHP，mysql进程出问题或高负载的时候相应过 慢怎么办，怎么切换的呢，这时就要用到脚本了，下面我们来看看keepalived是如何控制脚本来实现对服务器的监控和切换的写个脚本来实时监控三个服务，若有一个出现问题遍切换mkdir /root/shell/cd /root/shellvi keepcheck.sh

1. #!/bin/bash

2. while  :

3. do

4. mysqlcheck=`/usr/local/lnmp/mysql/bin/mysqladmin -uroot ping 2>&1`

5. mysqlcode=`echo $?`

6. phpcheck=`ps -C php-fpm --no-header | wc -l`

7. nginxcheck=`ps -C nginx --no-header | wc -l`

8. keepalivedcheck=`ps -C keepalived --no-header | wc -l`

9. if [ $nginxcheck -eq 0 ]|| [ $phpcheck -eq 0 ]||[ $mysqlcode -ne 0 ];then

10.                 if [ $keepalivedcheck -ne 0 ];then

11.                    killall -TERM keepalived

12.                 else

13.                    echo "keepalived is stoped"

14.                 fi

15.         else

16.                 if [ $keepalivedcheck -eq 0 ];then

17.                    /etc/init.d/keepalived start

18.                 else

19.                    echo "keepalived is running"

20.                 fi

21. fi

22. sleep 5

23. done

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注意，用/etc/init.d/keepalived start如果起不来，可以用/usr/local/keepalived/sbin/keepalived二进制文件直接执行启动即可

启动脚本：

1. chmod +x /root/shell/keepcheck.sh

2. nohup sh /root/shell/keepcheck.sh &

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节点B也用这个脚本

写入/etc/rc.local开机自动启动

1. echo "nohup sh /root/shell/keepcheck.sh &" >> /etc/rc.loal

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可以测试了

本文就写完了，这个可以用于生产环境，本人环境就这样配置的，但不同业务有不同环境，一定要按需调整，不要盲目盲从！