Wordpress installation problem, no permissions to write (Ubuntu / NGINX).

Here’s my setup:

• Fresh Ubuntu 14.04 64x installation.
• Fresh NGINX / MYSQL / PHP5-FPM / PHPMYADMIN installation.
• Installed POSTFIX and VSFTPD.
• umask has been changed to 002.
• the owner/group of the wordpress directory is myusername:myusername.
• myusername is also in the www-data group.
• All directories inside of wordpress are 775 with files being 664.

Regardless of the above, wordpress still cannot write config. This is a more underlining permisssion issue apparently, but I can’t figure out why. My solution are to chown -R the wordpress folder www-data:www-data and just go from there, however for security and work flow reasons that’s highly undesirable.

php is also running on www-data, and when I change the unix name/group to my username, any and all files can also write, but from what I read this is also highly undesirable.

I’d like a solution that doesn’t require me to do either of those. Any help would be appreciated.