No apache MPM package installed error

I'm getting "No apache MPM package installed" when trying to configure virtual hosts on apache2.2.

I compiled apache2.2 from source and I did not use --with-mpm=NAME option. I thought it will compile with default one then. So the question is, is there any way to check if MPM is installed indeed and I only need to enable it somewhere? If it is not, is there any way to add it without recompiling apache? Or, is there any way to have virtual hosts without it at all?

I was doing vhost configuration as per this example. Thanks in advance for your help ;)

EDIT: prefork is installed. The question is, why after a2ensite / a2dissite and /etc/init.d/apache2 reload I still get error "No MPM package installed"...

From serverfault Sejanus

• If you compiled it from source on Linux the default prefork mpm should have been installed. You should be able to list all modules including mpm's by running httpd -l. See the MPM documentation for more details

  Sejanus : Thanks. Thats right, it shows that prefork.c is compiled in indeed.
  From Kamil Kisiel

• In looking at the documentation at http://httpd.apache.org, I found that the virtual host is a core option. MPM is a process/thread management issue within the apache web server. Having or not having MPM should not be a determining factor in the support of virtual hosts.

  My guess therefore is that there are directives contained within your httpd.conf file are not consistent with the type of MPM modules are compiled into the apache server. For instance, you might be using the prefork MPM but the directives in the httpd.conf file would contain something like ThreadsperChild which is not appropriate. This could be the source of your error message.

  The Apache documentation further indicates that depending on the platform, there is a default MPM always selected by the configure process you go through. In Linux it is prefork.

  Sejanus : Thanks... I edited original question.
  From mdpc

• sudo apt-get install apache2

  Jeremy White : I was having the same problem, and this fixed it.
  From $pageUsers[$post.author].name