The easiest way find the process of an application running on the server is to type the following command:
ps aux | grep 'apache'This command would output a list of processes. I can see that the calling a /usr/sbin/apache2 is www-data. So the username of apache is www-data.
www-data 4126 0.0 0.3 32404 14296 ? S 12:28 0:00 /usr/sbin/apache2 -k start
www-data 4132 0.0 0.1 26048 4520 ? S 12:28 0:00 /usr/sbin/apache2 -k start
www-data 4134 0.0 0.3 32512 13964 ? S 12:28 0:00 /usr/sbin/apache2 -k start
www-data 4135 0.0 0.1 26048 4516 ? S 12:28 0:00 /usr/sbin/apache2 -k start
www-data 4145 0.0 0.3 31892 12964 ? S 12:29 0:00 /usr/sbin/apache2 -k start
</pre></blockquote>Note the address /usr/sbin/apache2 -k start. This indicates the command that launched the process. The first word of each process is its username. The username for apache is www-data.