Use absolute path for root directory

nginx.conf

@@ -17,7 +17,7 @@ http {
     server_name       localhost;
 
     location / {
-      root            html;
+      root            /usr/share/nginx/html;
       index           index.html index.htm;
       if ($request_method = 'OPTIONS') {
           add_header 'Access-Control-Allow-Origin' '*';