Apache2 reminders

apache2_reminders

The /etc/apache2/httpd.conf is empty in Ubuntu, because it is there for historic reasons
Apache2 user options should go into a new *.conf-file inside /etc/apache2/conf.d/
httpd.conf or apache2.conf may get overwritten during an update

To make sure the above works, check that /etc/apache2/apache2.conf contains the following lines:
Include conf.d/

In Apache 2.4+ the user configuration directory is /etc/apache2/conf-available/ 
Use a2enconf FILENAME_WITHOUT_SUFFIX to enable the new configuration file, or manually create a symlink in /etc/apache2/conf-enabled/
As of Apache 2.4 the configuration files must have the suffix .conf (e.g. conf-available/my-settings.conf)