If you use Gentoo and tried to install Cacti with Lighttpd instead of Apache, chances are that you ran into this error message :
/usr/lib/python2.6/site-packages/WebappConfig/content.py:27: DeprecationWarning: the md5 module is deprecated; use hashlib instead import md5, re, os, os.path * Fatal error: Your configuration file sets the server type "Apache" * Fatal error: but the corresponding package does not seem to be installed! * Fatal error: Please "emerge >=www-servers/apache-1.3" or correct your settings. * Fatal error(s) - aborting
You can solve that problem by editing the following file : /etc/vhosts/webapp-config and set vhost_server="lighttpd".
For further reference, you’ll also need the following USE flags for PHP :
spaghetti etc # grep php /etc/portage/package.use dev-lang/php cli cgi mysql xml session pcre sockets
The rest of the installation is pretty straight standard and is already well documented (here, there, or even there).