I’m prepping a domain on my VM server for Joomla installation, and they ask for a PHP module called, SUPHP (http://www.suphp.org/Home.html) to be installed.
On Ubuntu/Debian, it should suffice to apt-get install libapache2-mod-suphp.
libapache2-mod-suphp 0.7.1-1build1 Description: Apache2 module to run php scripts with the owner permissions With the use of the suphp setuid root binary (from suphp-common package), this Apache2 module change the uid of the process executing the PHP interpreter to the owner of the php script
But: Virtualmin already has an suexec system included, which can execute PHP as a user, and runs PHP scripts only from /home. Are you using Virtualmin?