Mod_rewrite not enabled?

I bought a PHP-based software that want to use the rewrite engine. But it complains that mod_rewrite is not enabled.
I wanted to check it via a2enmod.
But bash complains a2enmod: command not found.
How can I check if the mod_rewrite module is enabled?

a2enmod is an Apache webserver module. Cleavr supports Nginx as a web server not Apache so any Apache related modules/commands will not work with Cleavr provisioned servers.