如何利用FreeBSD搭建具有Keepalived和Nginx的高可用Web虚拟主机集群？

搭建Keepalived Nginx高可用Web集群的步骤如下：

1、安装FreeBSD操作系统

2、更新系统并安装必要的软件包

pkg update && pkg upgrade
pkg install nginx keepalived

3、配置Nginx虚拟主机

编辑/usr/local/etc/nginx/nginx.conf文件，添加以下内容：

http {
    ...
    include /usr/local/etc/nginx/sitesenabled/*;
    ...
}

创建一个名为default的虚拟主机配置文件/usr/local/etc/nginx/sitesavailable/default，并添加以下内容：

server {
    listen 80 default_server;
    listen [::]:80 default_server;
    root /usr/local/www/apache24/data;
    index index.html index.htm index.php;
    server_name _;
    location / {
        try_files $uri $uri/ =404;
    }
    error_page 404 /404.html;
    location = /404.html {
    }
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
    }
}

创建一个符号链接到sitesenabled目录：

ln s /usr/local/etc/nginx/sitesavailable/default /usr/local/etc/nginx/sitesenabled/default

4、配置Keepalived

编辑/usr/local/etc/keepalived/keepalived.conf文件，添加以下内容：

vrrp_script chk_nginx {
    script "/usr/local/etc/keepalived/check_nginx.sh"
    interval 2
    weight 2
}
vrrp_instance VI_1 {
    interface eth0
    state MASTER
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.1.100
    }
    track_script {
        chk_nginx
    }
}

创建一个检查Nginx状态的脚本/usr/local/etc/keepalived/check_nginx.sh，并添加以下内容：

#!/bin/sh
if pgrep "nginx" > /dev/null; then
    exit 0
else
    exit 1
fi

给脚本添加执行权限：

chmod +x /usr/local/etc/keepalived/check_nginx.sh

5、启动Nginx和Keepalived服务

service nginx start
service keepalived start

至此，你已经成功搭建了一个基于Keepalived和Nginx的高可用Web集群，当主服务器出现故障时，Keepalived会自动将虚拟IP切换到备用服务器，从而实现高可用性。