Thx for your answers. In the past (long time ago) I used the usemod-wiki. The only thing I was missing was a possibility for picture and file upload. (it is used in the intranet only, so no DOS protections are needed). It did not need a install at all (the whole wiki was one cgi-perl script). Backup was quite simple, I just send the plain files to me by mail and cron, so after a complete server and backup failure (gosh!), my wiki was one of the few parts that survived the big crash

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A usemod wiki with good file handling would be fine. (Probably today's usemod is able to do that, I will take a look).
Leo