Vanilla 2.1 - Ubuntu - Blank Screen on first load (instead of setup)
When installing Vanilla 2.1 on Ubuntu recently, I was greeted with a completely blank (empty) page, rather than the setup screen. Although I've managed to solve this (and it was simple enough), I couldn't find the answer online readily, so am posting it here incase it's useful to someone else!
Showed me that the problem was that 'json_decode' was not defined - this is because in Ubuntu (and potentially other distributions), the JSON functionality is in a separate package and must be installed explicitly.
apt-get install php5-json
service apache2 restart
Reload page - and voila, setup appears!