Modified wiki

Hey, not sure who I'm supposed to notify, but I modified the following page

http://wiki.ipfire.org/en/addons/cacti/start

I ran into an error with a Cacti install; it did not build the default database. I figure anyone installing Cacti would be comfortable on the command line, so I just added the information on how to do it.

Feel free to edit my edits. I'm not married to them, but did want to get the information out while it was fresh on my mind.

Rod