How to tell if Apache 2 is using prefork or worker MPM?
Answer:
If you are running in Red Hat Linux/ Fedora/ CentOS
# httpd -V
....
Architecture: 64-bit
Server MPM: Prefork
threaded: no
forked: yes (variable process count)
...
If you are running in Debian/ Ubuntu, you can use apache2 -V, which get the same output as above.