How to disable apache2 from running on startup
I was trying to remove the following warning from passenger-memory-stats, I had to install apache2 but without running it :
*** WARNING: The Apache executable cannot be found.
Please set the APXS2 environment variable to your ‘apxs2′ executable’s filename,
or set the HTTPD environment variable to your ‘httpd’ or ‘apache2′ executable’s filename.
Solution (found here) :