虽然看的一知半解，但是感觉有一天用到时会很有用，转

一、简介LVS是Linux Virtual Server的简写，意即Linux虚拟服务器，是一个虚拟的服务器集群系统。本项目在1998年5月由章文嵩博士成立，是中国国内最早出现的自由软件项目之一。目前有三种IP负载均衡技术（VS/NAT、VS/TUN和VS/DR）；十种调度算法（rr|wrr|lc|wlc|lblc|lblcr|dh|sh|sed|nq）。
Keepalived在这里主要用作RealServer的健康状态检查以及LoadBalance主机和BackUP主机之间failover的实现。LVS+Keepalived能实现的功能：利用LVS控制器主备模式避免单点故障以及自动删除故障WEB服务器结点并当它恢复后再自动添加到群集中。拓扑图：

二、系统环境系统平台：RHEL 5.4LVS版本：ipvsadm-1.24keepalived版本：keepalived-1.1.15三、安装1、在两台LVS Server上安装lvs、keepalived软件（LVS_MASTER & LVS_BACKUP）
lvs install -------------[root@LVS-MASTER ~]# wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.24.tar.gz[root@LVS-MASTER ~]# ln -s /usr/src/kernels/2.6.18-194.el5-i686//usr/src/linux/[root@LVS-MASTER ~]# tar zxvf ipvsadm-1.24.tar.gz[root@LVS-MASTER ~]# cd ipvsadm-1.24[root@LVS-MASTER ipvsadm-1.24]# make && make installKeepalived install -------------
[root@LVS-MASTER ~]# wget http://www.keepalived.org/software/keepalived-1.1.15.tar.gz[root@LVS-MASTER ~]# tar zxvf keepalived-1.1.15.tar.gz[root@LVS-MASTER ~]# cd keepalived-1.1.15[root@LVS-MASTER keepalived-1.1.15]# ./configure && make && make install######### 将keepalived做成启动服务，方便管理##########[root@LVS-MASTER ~]# cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/[root@LVS-MASTER ~]# cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/[root@LVS-MASTER ~]# mkdir /etc/keepalived/[root@LVS-MASTER ~]# cp /usr/local/etc/keepalived/keepalived.conf /etc/keepalived/[root@LVS-MASTER ~]# cp /usr/local/sbin/keepalived /usr/sbin/[root@LVS-MASTER ~]# service keepalived start | stop2、keepalived的配置################### MASTER ###################

! Configuration File for keepalived

global_defs {
notification_email {
root@linux.tang.chao #设置报警邮件地址，可以设置多个，每行一个。 mchina_tang@qq.com #需开启本机的sendmail服务
}

notification_email_from keepalived@localhost #设置邮件的发送地址
smtp_server 127.0.0.1 #设置smtp server地址
smtp_connect_timeout 30 #设置连接smtp server的超时时间
router_id LVS_DEVEL #表示运行keepalived服务器的一个标识。发邮件时显示在邮件主题的信息
}

vrrp_instance VI_1 {

#指定keepalived的角色，MASTER表示此主机是主服务器，BACKUP表示此主机是备用服务器
state MASTER

#指定HA监测网络的接口
interface eth0

#虚拟路由标识，这个标识是一个数字，同一个vrrp实例使用唯一的标识。即同一vrrp_instance下，MASTER和BACKUP必须是一致的
virtual_router_id 51

#定义优先级，数字越大，优先级越高，在同一个vrrp_instance下，MASTER的优先级必须大于BACKUP的优先级
priority 100

#设定MASTER与BACKUP负载均衡器之间同步检查的时间间隔，单位是秒
advert_int 1

#设置验证类型和密码
authentication {

#设置验证类型，主要有PASS和AH两种
auth_type PASS

##设置验证密码，在同一个vrrp_instance下，MASTER与BACKUP必须使用相同的密码才能正常通信
auth_pass 1111
}

#设置虚拟IP地址，可以设置多个虚拟IP地址，每行一个
virtual_ipaddress {
10.0.0.148
}
}

#设置虚拟服务器，需要指定虚拟IP地址和服务端口，IP与端口之间用空格隔开
virtual_server 10.0.0.148 80 {

#设置运行情况检查时间，单位是秒
delay_loop 6

#设置负载调度算法，这里设置为rr，即轮询算法
lb_algo rr
#设置LVS实现负载均衡的机制，有NAT、TUN、DR三个模式可选
lb_kind DR

#会话保持时间，单位是秒。这个选项对动态网页是非常有用的，为集群系统中的session共享提供了一个很好的解决方案。
#有了这个会话保持功能，用户的请求会被一直分发到某个服务节点，直到超过这个会话的保持时间。
#需要注意的是，这个会话保持时间是最大无响应超时时间，也就是说，用户在操作动态页面时，如果50秒内没有执行任何操作，
#那么接下来的操作会被分发到另外的节点，但是如果用户一直在操作动态页面，则不受50秒的时间限制
persistence_timeout 50
#指定转发协议类型，有TCP和UDP两种
protocol TCP

#配置服务节点1，需要指定real server的真实IP地址和端口，IP与端口之间用空格隔开
real_server 10.0.0.137 80 {
#配置服务节点的权值，权值大小用数字表示，数字越大，权值越高，设置权值大小可以为不同性能的服务器
#分配不同的负载，可以为性能高的服务器设置较高的权值，而为性能较低的服务器设置相对较低的权值，这样才能合理地利用和分配系统资源
weight 3

#realserver的状态检测设置部分，单位是秒
TCP_CHECK {
#表示3秒无响应超时
connect_timeout 10

#表示重试次数
nb_get_retry 3

#表示重试间隔
delay_before_retry 3
connect_port 80
}
}

real_server 10.0.0.139 80 {
weight 3
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
}

#################### BACKUP ###################
! Configuration File for keepalivedglobal_defs { notification_email { root@linux.tang.chao mchina_tang@qq.com } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL}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 { 10.0.0.148 }}virtual_server 10.0.0.148 80 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 10.0.0.137 80 { weight 3 TCP_CHECK { connect_timeout 10 nb_get_retry 3 delay_before_retry 3 connect_port 80 } } real_server 10.0.0.139 80 { weight 3 TCP_CHECK { connect_timeout 10 nb_get_retry 3 delay_before_retry 3 connect_port 80 } }}

3、在两台Web Server上执行realserver.sh脚本，为lo:0绑定VIP地址10.0.0.148、抑制ARP广播。[root@web1 ~]# cat realserver.sh
#!/bin/bash
#description: Config
realserverVIP=10.0.0.148
/etc/rc.d/init.d/functions
case "$1" in
start)
/sbin/ifconfig lo:0 $VIP netmask 255.255.255.255 broadcast $VIP
/sbin/route add -host $VIP dev lo:0
echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo "2" >/proc/sys/net/ipv4/conf/lo/arp_announce
echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo "2" >/proc/sys/net/ipv4/conf/all/arp_announce sysctl -p >/dev/null 2>&1
echo "RealServer Start OK"
;;
stop)
/sbin/ifconfig lo:0 down
/sbin/route del $VIP >/dev/null 2>&1
echo "0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo "0" >/proc/sys/net/ipv4/conf/lo/arp_announce
echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
echo "RealServer Stoped"
;;
*)
echo "Usage: $0 {start|stop}"
exit 1
esac
exit 0

[root@web1 ~]# sh realserver.sh start
4、分别在LVS-MASTER、LVS-BACKUP上执行service keepalived start启动keepalived就可实现负载均衡及高可用集群了；[root@LVS-MASTER keepalived]# service keepalived start[root@LVS-MASTER keepalived]# ipvsadm -L
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.0.148:http rr persistent 50
-> 10.0.0.139:http Route 3 0 0
-> 10.0.0.137:http Route 3 0 0
[root@LVS-MASTER keepalived]#查看日志/var/log/messages[root@LVS-MASTER keepalived]# tail -n 30/var/log/messages
Apr 19 03:59:58 LVS-MASTER avahi-daemon[2845]: Withdrawing address record for10.0.0.148 on eth0.
Apr 19 04:00:19 LVS-MASTER Keepalived: Starting Keepalived v1.2.1 (04/17,2012)
Apr 19 04:00:19 LVS-MASTER Keepalived: Starting Healthcheck child process,pid=5960
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Netlink reflector reportsIP 10.0.0.136 added
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Netlink reflector reportsIP 10.0.0.159 added
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Registering Kernelnetlink reflector
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Registering Kernelnetlink command channel
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Configuration is using :12257 Bytes
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Using LinkWatch kernelnetlink reflector...
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Activating healtcheckerfor service [10.0.0.137:80]
Apr 19 04:00:19 LVS-MASTER Keepalived_healthcheckers: Activating healtcheckerfor service [10.0.0.139:80]
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Netlink reflector reports IP10.0.0.136 added
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Netlink reflector reports IP10.0.0.159 added
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Registering Kernel netlinkreflector
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Registering Kernel netlink commandchannel
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Registering gratutious ARP sharedchannel
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Opening file'/etc/keepalived/keepalived.conf'.
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Configuration is using : 36698Bytes
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: Using LinkWatch kernel netlinkreflector...
Apr 19 04:00:19 LVS-MASTER Keepalived_vrrp: VRRP sockpool: [ifindex(2),proto(112), fd(11,12)]
Apr 19 04:00:19 LVS-MASTER Keepalived: Starting VRRP child process, pid=5961
Apr 19 04:00:20 LVS-MASTER Keepalived_vrrp: VRRP_Instance(VI_1) Transition toMASTER STATE
Apr 19 04:00:21 LVS-MASTER Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTERSTATE
Apr 19 04:00:21 LVS-MASTER Keepalived_vrrp: VRRP_Instance(VI_1) settingprotocol VIPs.
Apr 19 04:00:21 LVS-MASTER Keepalived_vrrp: VRRP_Instance(VI_1) Sendinggratuitous ARPs on eth0 for 10.0.0.148
Apr 19 04:00:21 LVS-MASTER Keepalived_healthcheckers: Netlink reflector reportsIP 10.0.0.136 added
Apr 19 04:00:21 LVS-MASTER avahi-daemon[2845]: Registering new address recordfor 10.0.0.148 on eth0.
Apr 19 04:00:21 LVS-MASTER Keepalived_vrrp: Netlink reflector reports IP10.0.0.136 added
Apr 19 04:00:26 LVS-MASTER Keepalived_vrrp: VRRP_Instance(VI_1) Sendinggratuitous ARPs on eth0 for 10.0.0.148
[root@LVS-MASTER keepalived]#四、测试接下来做高可用性测试&故障切换测试......####高可用性测试####模拟故障，将LVS-MASTER上的keepalived服务停掉，然后观察LVS-BACKUP上的日志，信息如下[root@LVS-BACKUP keepalived]# tail -f /var/log/messages
Apr 19 03:33:04 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1)Transition to MASTER STATE
Apr 19 03:33:05 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTERSTATE
Apr 19 03:33:05 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) settingprotocol VIPs.
Apr 19 03:33:05 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) Sendinggratuitous ARPs on eth0 for 10.0.0.148
Apr 19 03:33:05 LVS-BACKUP Keepalived_vrrp: Netlink reflector reports IP10.0.0.157 added
Apr 19 03:33:05 LVS-BACKUP Keepalived_healthcheckers: Netlink reflector reportsIP 10.0.0.157 added
Apr 19 03:33:05 LVS-BACKUP avahi-daemon[2825]: Registering new address recordfor 10.0.0.148 on eth0.
Apr 19 03:33:10 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) Sendinggratuitous ARPs on eth0 for 10.0.0.148从日志中可知，主机出现故障后，备机立刻检测到，此时备机变为MASTER角色，并且接管了主机的虚拟IP资源，最后将虚拟IP绑定在etho设备上。将LVS-MASTER 上的keepalived服务开启后，LVS-BACKUP的日志状态。Apr 19 03:34:02 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) Received higher prio advert
Apr 19 03:34:02 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1)Entering BACKUP STATE
Apr 19 03:34:02 LVS-BACKUP Keepalived_vrrp: VRRP_Instance(VI_1) removing protocol VIPs.
Apr 19 03:34:02 LVS-BACKUP Keepalived_vrrp: Netlink reflector reports IP 10.0.0.157 removed
Apr 19 03:34:02 LVS-BACKUP Keepalived_healthcheckers: Netlink reflector reports IP 10.0.0.157 removed
Apr 19 03:34:02 LVS-BACKUP avahi-daemon[2825]: Withdrawing address record for 10.0.0.148 on eth0.从日志可知，备机在检测到主机重新恢复正常后，释放了虚拟IP资源重新成为BACKUP角色####故障切换测试####故障切换是测试当某个节点出现故障后，Keepalived监制模块是否能及时发现然后屏蔽故障节点，同时将服务器转移到正常节点来执行。将web2节点服务停掉，假设这个节点出现故障，然后主、备机日志信息如下Apr 19 03:35:04 LVS-MASTER Keepalived_healthcheckers:TCP connection to [10.0.0.139:80] failed!!!
Apr 19 03:35:04 LVS-MASTER Keepalived_healthcheckers:Removing service [10.0.0.139:80] from VS [10.0.0.148:80]
Apr 19 03:35:04 LVS-MASTER Keepalived_healthcheckers: Remote SMTP server [127.0.0.1:25] connected.[root@LVS-MASTER keepalived]# ipvsadm -L
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.0.148:http rr persistent 50
-> 10.0.0.137:http Route 3 0 0
[root@LVS-MASTER keepalived]#从以上可以看出，Keepalived监控模块检测到10.0.0.139这台主机出现故障后，将些web2从集群系统中剔除掉了。 此时访问http://10.0.0.148只能看到web1了)

重新启动web2节点的服务，日志信息如下：Apr 19 03:38:22 LVS-MASTER Keepalived_healthcheckers:TCP connection to [10.0.0.139:80] success.
Apr 19 03:38:22 LVS-MASTER Keepalived_healthcheckers:Adding service [10.0.0.139:80] to VS [10.0.0.148:80]
Apr 19 03:38:22 LVS-MASTER Keepalived_healthcheckers: Remote SMTP server [127.0.0.1:25] connected.[root@LVS-MASTERkeepalived]# ipvsadm -L
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.0.0.148:http rr persistent 50
-> 10.0.0.139:http Route 3 0 0
-> 10.0.0.137:http Route 3 0 0
[root@LVS-MASTER keepalived]#Keepalived监控模块检测到10.0.0.139这台主机恢复正常后，又将此节点加入集群系统中，再次访问就可以访问到web2页面了）