今天在CentOS8部署lemp环境部署完毕后提示502 Bad Gateway错误，查看/var/log/nginx/error.log日志发现错误内容：

2020/12/16 18:14:45 [error] 5574#0: *15 connect() failed (111: Connection refused) while connecting to upstream, client: 49.72.84.213, server: towait.com, request: "GET / HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "www.towait.com"

第一反应是php-fpm连接失败，于是查看文件/etc/php-fpm.d/www.conf中的端口监听参数写的是

listen = /run/php-fpm/www.sock

而nginx.conf文件中fastcgi_pass参数后面写的是127.0.0.1:9000，于是修改一下：

fastcgi_pass unix:/run/php-fpm/www.sock; 

重启nginx，问题解决。

问题补充

1.访问php文件会直接被下载

这是由于缺失php脚本解析的配置，在server{...}配置区域中加入下面参数即可

	location ~ \.php$ {        
		fastcgi_pass unix:/run/php-fpm/www.sock;         
		fastcgi_index index.php;         
		fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;        
		include fastcgi_params; 
	 }       
}

这是一份完整的nginx文件参数

server {
	listen 80;
	server_name sipmv.com www.sipmv.com;
	root /mnt/www/sipmv.com/public_html/;
	index index.php index.html index.htm;

	access_log /var/log/nginx/sipmv.com.access.log;
	error_log /var/log/nginx/sipmv.com.error.log;

	location ~ \.php$ {        
		fastcgi_pass unix:/run/php-fpm/www.sock;         
		fastcgi_index index.php;         
		fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;        
		include fastcgi_params; 
	 }       
}