迁移至Ubuntu24.04 Nginx时出现server_name冲突报错求助

问题背景 #

从CentOS7+Apache迁移到Ubuntu24.04+Nginx后，出现警告：

nginx: [warn] 25570#25570: conflicting server name "www.example.com" on 0.0.0.0:80, ignored

附上当前Nginx配置文件请求排查。

配置文件内容 #

server {
    server_name example.com www.example.com;
    root /var/www/example.com;

    index index.html index.php;

    location / {
       try_files $uri $uri/ /index.php?$query_string;
     }

       location ~* /(\.git|cache|bin|logs|backup|tests)/.*$ { return 403; }
       location ~* /(system|vendor)/.*\.(txt|xml|md|html|yaml|yml|php|pl|py|cgi|twig|sh|bat)$ { return 403; }
       location ~* /user/.*\.(txt|md|yaml|yml|php|pl|py|cgi|twig|sh|bat)$ { return 403; }
       location ~ /(LICENSE\.txt|composer\.lock|composer\.json|nginx\.conf|web\.config|htaccess\.txt|\.htaccess) { return 403; }

    location ~ \.php$ {
       fastcgi_pass unix:/var/run/php/php8.3-fpm.sock;
       fastcgi_split_path_info ^(.+\.php)(/.+)$;
       fastcgi_index index.php;
       include fastcgi_params;
       fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
     }

    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}

server {
    if ($host = example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

    listen 80;
    server_name example.com www.example.com;
    return 404; # managed by Certbot
}

问题分析 #

警告的核心原因是80端口的监听配置中，www.example.com被重复声明，同时当前配置的80端口server块存在逻辑错误：

1. Certbot生成的if ($host = example.com)仅处理主域名的HTTPS跳转，www.example.com访问80端口会直接返回404，不符合预期。
2. 若服务器上存在其他Nginx配置文件（如默认的default.conf），其未指定server_name或也声明了www.example.com，会触发冲突警告。

修复方案 #

步骤1：检查并清理冲突配置 #

执行命令查看启用的配置文件：

ls /etc/nginx/sites-enabled/

如果存在default等无关配置文件，执行以下命令禁用：

sudo unlink /etc/nginx/sites-enabled/default

步骤2：修正80端口跳转逻辑 #

将原80端口的server块替换为以下内容，实现主域名与www域名统一跳转到HTTPS：

server {
    listen 80;
    server_name example.com www.example.com;

    # 所有HTTP请求强制跳转HTTPS
    return 301 https://$host$request_uri;
}

步骤3：验证配置并重启服务 #

执行配置合法性检查：

sudo nginx -t

若输出test is successful，重启Nginx服务：

sudo systemctl reload nginx

补充说明 #

你关于“主域名与子域名放在同一server_name行”的理解是正确的，问题并非出在该配置上，而是80端口的跳转逻辑错误+潜在的配置文件冲突导致的警告。

内容的提问来源于stack exchange，提问作者zoof