How to activatie "shell_exec"?

General questions
1

Hello Piwik,

I just use Piwik and I found in: Diagnostic >SystemCheck the following warning:

There are some issues with your system. Piwik will run, but you might experience some minor problems. See below for more information.

Below I found the following:

Other functions shell_exec
You need to enable this built-in function.

I’ve searched some, but I cannot find where I can enable this build-in function.

Who does know where I can enable it.

Thanks.

2

It seems that shell_exec is not in my php.ini files.
I am on Ubuntu 14.04 - PHP 5.5.9-1ubuntu4.14

I am wondering if this is an error in the system check as the PHP version is newer possibly than what is being checked?