I'm trying to wrap my head around unix permissions. The problem I'm having is that Wordpress isn't able to update itself... instead it's giving me an FTP prompt. On the Wordpress website it clearly says that this is normal behavior when Wordpress doesn't have correct unix permissions setup.

So from what I understand I need to give the unix user which Wordpress operates with, correct permissions?

Running echo exec('groups') returns www-data
Running echo exec('whoami') returns www-data

But even after changing the file owner to www-data on almost every file and folder it still doesn't work.

I'm sure it's something very basic that I'm missing...

Do I need to restart some service after I changed permissions?

Any idea what I should do?

Help/guidance is appreciated!