@khoinguyen1407
In ../cops/config_local.php set (if using apache)
Code:
/*
* Wich header to use when downloading books outside the web directory
* Possible values are :
* X-Accel-Redirect : For Nginx
* X-Sendfile : For Lightttpd or Apache (with mod_xsendfile)
* No value (default) : Let PHP handle the download
*/
$config['cops_x_accel_redirect'] = "X-Sendfile";
and try again.
In apache2 first enable mod_xsendfile (from terminal: a2enmod x-sendfile)
Hope this works, let us know.