PHP exec disable - Synology DS

Hey there,
I have a tracking problem with my Piwik installation.
It tracks only local accessing. I found this error:

There is an error. Please report the message (Piwik 1.10.1) and full backtrace in the Piwik forums (please do a Search first as it might have been reported already!).

Warning: exec(): PHP exec disable. in /volume1/web/piwik/core/Piwik.php on line 2748 

Backtrace -->

#0 Piwik_ErrorHandler(...) called at [:]
#1 exec(...) called at [/volume1/web/piwik/core/Piwik.php:2748]
#2 Piwik::checkIfFileSystemIsNFS(...) called at [/volume1/web/piwik/plugins/Installation/Controller.php:875]
#3 Piwik_Installation_Controller::getSystemInformation(...) called at [/volume1/web/piwik/plugins/Installation/Controller.php:946]
#4 Piwik_Installation_Controller->setupSystemCheckView(...) called at [/volume1/web/piwik/plugins/Installation/Controller.php:503]
#5 Piwik_Installation_Controller->systemCheckPage(...) called at [:]
#6 call_user_func_array(...) called at [/volume1/web/piwik/core/FrontController.php:138]
#7 Piwik_FrontController->dispatch(...) called at [/volume1/web/piwik/index.php:53]

What’s the problem? Last time the error was because the Password of the piwik-user was lost. Now there isn’t any piwik user configured.
I’m sorry for my basic English, but I heard that it’s better if we post bug’s in the English Forum instead of the German part.

Thanks for helping me!