Thank you for your comments about the MediaWiki.
The official MediaWiki instructions are not oriented towards Debian/(K)Ubuntu because the installation directory structure is much different. Debian/(K)Ubuntu makes very liberal use of virtual directories (as you may notice if you have installed the Debian package ansd spend a lot of time poking around).
It makes it tricky to define directories in the same manner as the instructions relate.
Do you already have one or more wikis running using the Debian/(K)Ubuntu package? If so, I would welcome suggestions on changing the instructions. I have a wiki farm of over 20 wikis on a single server, and it took a long time to work out the kinds. I have never had a security breach (PS although I edit Ubuntuguide.org, it is not actually one of the wikis on my servers and is not under my control. Ubuntuguide.org, in fact, is far less secure than my own wiki farm, which includes Kubuntuguide.info among others).
To be perfectly honest, I don't use the line you referenced in my wiki farm, because i agree about not using the installation root folder as the data folder for any one of the wikis. However, I have come to no harm with it either. The reason for the proscription, I suspect, is so that the installation folder can be updated without risking an individualised wiki's data. (In truth it doesn't matter; every upgrade risks data loss to a wiki, anyway becasue the PHP code does not always match the database.)
Still, I am willing to revisit my MediaWiki instructions (which took me about a year to work out because the MediaWiki instructions often don't actually work on Debian) if you have specific recommendations for instruction revisions.
Perspectoff 04:13, 6 December 2011 (UTC)