You need to get the URL straight.
linuxhost/index.php is incomplete, but may fall back to
http://linuxhost/index.php by default (in your browser).
//linuxhost/index.php, as the box indicates, falls back to something like file://linuxhost/index.php. But this is most likely browser behaviour, not server behaviour. So I doubt if you can configure it in httpd.conf.
So the problem is that you need to use the right URL to get the stuff you want. The protocol information (
http://, file://, etc) is there for a purpose. I doubt if you can avoid it from the server's side.