title: NGINX - FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream
body: <p>I got this error message when trying to set WordPress as a subdirectory. <code>File not found.</code> when view the URL <code>example.com/blog</code></p>
  
  <pre><code>2020/05/05 20:55:56 [error] 906#906: *1 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: xxx.xxx.xxx.xxx, server: example.com, request: "GET /blog/ HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.2-fpm.sock:", host: "example.com"
  </code></pre>
  
  <p>example.conf</p>
  
  <pre><code>server {
      server_name example.com www.example.com;
      root /var/www/example/public;
  
      add_header X-Frame-Options "SAMEORIGIN";
      add_header X-XSS-Protection "1; mode=block";
      add_header X-Content-Type-Options "nosniff";
  
      index index.html index.htm index.php;
  
      charset utf-8;
  
      location / {
          try_files $uri $uri/ /index.php?$query_string;
      }
  
      location = /favicon.ico { access_log off; log_not_found off; }
      location = /robots.txt  { access_log off; log_not_found off; }
  
      error_page 404 /index.php;
  
      location /blog {
          alias /var/www/blog;
          index   index.html index.htm index.php;
          try_files $uri $uri/ /blog/index.php?$args;
      }
  
      location ~ \.php$ {
          fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
          fastcgi_index index.php;
          fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
          include fastcgi_params;
      }
  
      location ~ /\.(?!well-known).* {
          deny all;
      }
  }
  </code></pre>