keepalived的工作原理基于三個層面，分別時IP層，TCP層和應用層
IP
層：keepalived會定期向服務器集群中的服務器發送一個類似于ping程序的ICMP數據包。通俗理解就是我keepalived來ping你服
務器，我要是ping通了，那我知道你還活著，咱們可以繼續合作，如果不幸發現你掛了，那就得把這臺服務器踢了。該層就是確保服務器ip地址有效，一次來
判斷這臺服務器可否繼續在崗謀職。
TCP層：這一層和IP層類似，只不過IP層檢查的是IP，該層檢查TCP端口。keepalived在IP層
且報你服務器的IP有效，然后繼續看你的TCP端口，比如說你是web
server，那你的80端口就應該開啟，如果keepalived發現你的80端口沒有啟動。那么它就會認為你已經掛掉，然后剔除。
應用層：這一層就是具體的工作程序了，keepalived是個恪盡職守的檢察官，應用層的程序與用戶的設定息息相關，keepalived則通過檢查服務器的運行是否和用戶設定一致，如果不一致，keepalived就會宣判這臺服務器犧牲。
主機：172.25.44.3 server3
備機：172.25.44.4 server4
[root@server3 ～]# vim /etc/sysconfig/network-scripts/ifcfg-eth0:0DEVICE=eth0:0TYPE=EthernetONBOOT=yesBOOTPROTO=staticDNS1=172.25.44.44IPADDR=172.25.44.100NETMASK=255.255.255.0GETWAY=172.25.44.44[root@server3 ～]# /etc/init.d/network restart[root@server3 ～]# ifconfigeth0 Link encap:Ethernet HWaddr 52:54:00:48:60:3E inet addr:172.25.44.4 Bcast:172.25.44.255 Mask:255.255.255.0 inet6 addr: fe80::5054:ff:fe48:603e/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11926 errors:0 dropped:0 overruns:0 frame:0 TX packets:6533 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:25662550 (24.4 MiB) TX bytes:876645 (856.0 KiB) eth0:0 Link encap:Ethernet HWaddr 52:54:00:48:60:3E inet addr:172.25.44.100 Bcast:172.25.44.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:36283 errors:0 dropped:0 overruns:0 frame:0 TX packets:36283 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1982812 (1.8 MiB) TX bytes:1982812 (1.8 MiB)
安裝包：nginx-1.10.3.tar.gz
解壓安裝包：tar zxf nginx-1.10.3.tar.gz
[root@server3 software]# cd nginx-1.10.3 —prefix=/usr/local/lnmp/nignx [root@server3 nginx-1.10.3]# ./configure [root@server3 nginx-1.10.3]# make [root@server3 nginx-1.10.3]# make install [root@server3 nginx-1.10.3]# ln -s /usr/local/lnmp/nginx/sbin/nginx /usr/local/sbin/ #創建nginx的軟鏈接
[root@server3 nginx-1.10.3]# cd /usr/local/lnmp/nginx/conf[root@server3 conf]# vim nginx.conf/#訪問8088端口是的發布目錄為/var/www/html，而nginx的默認發布目錄還是/usr/local/lnmp/nginx/html
server { listen 8088；#監聽8088端口 server_name localhost;
location / {
root /var/www/html;
index index.html index.htm;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/local/lnmp/nginx/html;
}
}
[root@server3 conf]# cd /var/www/html[root@server3 html]# vim index.html
<html>
<head>
<title>Welcome to nginx!</title>
</head>
<body bgcolor="white" text="black">
<center><h2>Welcome to nginx! 172.25.44.3</h2></center>
</body>
</html>
[root@server3 html]# nginx安裝包：keepalived-1.2.2.tar.gz
[root@server3 software]# wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz [root@server3 software]# tar zxf keepalived-1.2.2.tar.gz [root@server3 software]# cd keepalived-1.2.2 [root@server3 keepalived-1.2.2]# ./configure [root@server3 keepalived-1.2.2]# make [root@server3 keepalived-1.2.2]# make install [root@server3 keepalived-1.2.2]# cp /usr/local/sbin/keepalived /usr/sbin/ [root@server3 keepalived-1.2.2]# cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/ [root@server3 keepalived-1.2.2]# cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/ [root@server3 keepalived-1.2.2]# cp -r /usr/local/etc/keepalived/ /etc/
[root@server3 keepalived-1.2.2]# vim /var/www/html/index.html
global_defs {
router_id LVS_DEVEL
}
vrrp_script chk_http_port {
script “</dev/tcp/127.0.0.1/8088”
interval 1
weight -2
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
172.25.44.100
}
track_script {
chk_http_port
}[root@server3 keepalived-1.2.2]# /etc/init.d/keepalived start
備機次同步主機的操作步驟：keepalived的配置文件中，主機的state為MASTER，備機的state為BACKUP，備機的priority要小于主機
[root@server3 software]# /etc/init.d/keepalived stop Stopping keepalived: [ OK ]
[root@server4 conf]# ip a 1: lo: mtu 16436 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: mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 52:54:00:48:60:3e brd ff:ff:ff:ff:ff:ff inet 172.25.44.4/24 brd 172.25.44.255 scope global eth0 inet 172.25.254.104/24 brd 172.25.254.255 scope global eth0 inet 172.25.44.100/32 scope global eth0 inet 172.25.44.100/24 brd 172.25.44.255 scope global secondary eth0:0 inet6 fe80::5054:ff:fe48:603e/64 scope link valid_lft forever preferred_lft forever
[root@server3 software]# /etc/init.d/keepalived start Starting keepalived: [ OK ]
[root@server3 software]# ip a 1: lo: mtu 16436 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: mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 52:54:00:b4:14:0d brd ff:ff:ff:ff:ff:ff inet 172.25.44.3/24 brd 172.25.44.255 scope global eth0 inet 172.25.254.103/24 brd 172.25.254.255 scope global eth0 inet 172.25.44.100/32 scope global eth0 inet6 fe80::5054:ff:feb4:140d/64 scope link valid_lft forever preferred_lft forever
[root@server3 software]# killall nginx
問題補充：在備機keepalived的配合配置文件中，如果補修改state的情況下實驗也是可以成功的，我覺得應該時兩個機子通過priority優先級競爭。
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