How to upgrade from Wakaba Zero:
res/ files of Wakaba Zero aren't entirely compatible with Kareha, and need to be updated.zeroconv.pl does this, and creates a new directory named _res that contains the updated files. Run this script in the Wakaba Zero directory first of all. It will not convert ALL information, sadly - image checksums and passwords are lost, so users can't delete old posts, and people can post dupes to the old images. This didn't seem like a big enough problem that I felt like fixing it.mode_image/ directory. Edit config.pl to your liking - copying the old directly will probably not work. Some options are the same, some aren't.src/, thumb/ and _res/ directories from the old Wakaba Zero directory to the new Kareha directory. Rename res_/ as res/.Hopefully, you should now have a working board again.
Addendum: I seem to have forgotten to implement an easy way to rebuild caches from the web interface in the image board version, so to do it you'll either have to hit http://.../kareha.pl?task=rebuild&admin=ADMIN_PASS or just delete index.html and hit kareha.pl.