keepalived是一个用于做双机热备（HA）的软件，常和haproxy联合起来做热备＋负载均衡，达到高可用
1. 实验环境
Master:10.20.2.233
Backup:10.20.2.235
虚拟IP:10.20.2.238
2. Keepalived安装
1) 通过yum安装软件依赖包
yum install -y wget make gcc openssl-devel popt-devel
2) Keepalived源码包下载安装
下载地址：http://www.keepalived.org/software/keepalived-1.2.23.tar.gz
tar -zxf keepalived-1.2.23.tar.gz -C /usr/src
cd /sru/src/keepalived-1.2.23/
./configure --prefix=/usr/local/keepalived/
Make
make install
3) 安装成功后做成服务模式
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/
3. 编辑配置文件
mkdir -p /etc/keepalived
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
1) Master配置文件内容如下：
! Configuration File for keepalived
global_defs {
router_id HA_TEST
}
#监测haproxy进程状态，每2秒执行一次
vrrp_script chk_haproxy {
script "/etc/keepalived/check_haproxy.sh"
interval 2
weight 2
}
vrrp_instance VI_1 {
state MASTER # 从为BACKUP
priority 200 # 从为100
virtual_router_id 51 #路由ID，可通过#tcpdump vrrp查看。
garp_master_delay 1 #主从切换时间，单位为秒。
interface eth0
advert_int 1
mcast_src_ip 10.20.2.233 #MASTER服务器IP,从服务器写从服务器的IP
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.20.2.238 #虚拟IP
}
track_script {
chk_haproxy #监测haproxy进程状态
}
}
2) BACKUP配置文件内容如下：
! Configuration File for keepalived
global_defs {
router_id HA_TEST
}
#监测haproxy进程状态，每2秒执行一次
vrrp_script chk_haproxy {
script "/etc/keepalived/check_haproxy.sh"
interval 2
weight 2
}
vrrp_instance VI_1 {
state BACKUP # 主为MASTER
priority 100 # 主为101
virtual_router_id 51 #路由ID，可通过#tcpdump vrrp查看。
garp_master_delay 1 #主从切换时间，单位为秒。
interface eth0
advert_int 1
mcast_src_ip 10.20.2.235 #BACKUP服务器IP,主服务器写主服务器的IP
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
10.20.2.238 #虚拟IP
}
track_script {
chk_haproxy #监测haproxy进程状态
}
}
3) haproxy检测脚本（check_haproxy.sh）内容如下
#!/bin/bash
A=`ps -C haproxy --no-header |wc -l`
if [ $A -eq 0 ];then
/etc/init.d/haproxyd start
sleep 3
if [ `ps -C haproxy --no-header |wc -l` -eq 0 ];then
/etc/init.d/keepalived stop
fi
Fi
chmod 755 /etc/keepalived/check_haproxy.sh #脚本编写完成后需要赋上权限
4) Keepalived的启停
service keepalived start #停止
service keepalived stop #启动
service keepalived restart #重启
4. 测试：
1) 启动MASTER和BACKUP上的keepalived
service keepalived start （keepalived启动的同时会将haproxy启动）
[root@test keepalived]# service keepalived start
Starting keepalived: [ OK ]
[root@test keepalived]# service haproxyd status
HAProxy(pid 32077) is running!
MASTER绑定了VIP,BACKUP未绑定VIP
[root@test keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
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 00:50:56:85:46:b2 brd ff:ff:ff:ff:ff:ff
inet 10.20.2.233/24 brd 10.20.2.255 scope global eth0
inet 10.20.2.238/32 scope global eth0
inet6 fe80::250:56ff:fe85:46b2/64 scope link
valid_lft forever preferred_lft forever
[root@dengqp01 keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
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 00:50:56:85:73:ce brd ff:ff:ff:ff:ff:ff
inet 10.20.2.235/24 brd 10.20.2.255 scope global eth0
inet6 fe80::250:56ff:fe85:73ce/64 scope link
valid_lft forever preferred_lft forever
2) 停止主上的haproxy，3秒后，keepalived会将其启动
[root@test keepalived]# service haproxyd stop
STOP HAProxy Listen
STOP HAProxy process
[root@test keepalived]# service haproxyd status
HAProxy(pid 32368) is running!
3) 停止主上的keepalived，备机马上接管服务
BACKUP上绑定了VIP
[root@dengqp01 keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
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 00:50:56:85:73:ce brd ff:ff:ff:ff:ff:ff
inet 10.20.2.235/24 brd 10.20.2.255 scope global eth0
inet 10.20.2.238/32 scope global eth0
inet6 fe80::250:56ff:fe85:73ce/64 scope link
valid_lft forever preferred_lft forever
4) 启动主上的keepalived，MASTER绑定VIP，BACKUP释放了VIP
[root@test keepalived]# service keepalived start
Starting keepalived: [ OK ]
[root@dengqp01 keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
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 00:50:56:85:73:ce brd ff:ff:ff:ff:ff:ff
inet 10.20.2.235/24 brd 10.20.2.255 scope global eth0
inet 10.20.2.238/32 scope global eth0
inet6 fe80::250:56ff:fe85:73ce/64 scope link
valid_lft forever preferred_lft forever
