We were having issues getting the one-click installer to work.
We ended-up changing the owner/group of our wordpress folder, and all files/folders inside, to www-data/www-data.
So, let's say our WP folder lives here:
Using the shell:
$ cd /blah/ $ sudo chown -R www-data:www-data wp $ cd wp $ sudo chown -R www-data:www-data *
In other words, not only did everything inside the WP folde need to have owner/group be www-data, the parent folder that houses the WP install needed www-data owner/group permissions.
Just wanted to post this info for others in the same predicament.