Installing Wordpress with Nginx stop

Hi! I’m follow this guide: https://www.digitalocean.com/community/tutorials/how-to-install-wordpress-with-nginx-on-ubuntu-14-04

I’m stuck in step four, here:

" The group that nginx operates under is www-data. For the user portion, enter your user account name. We will demonstrate with an account called demo here:

sudo chown -R demo:www-data /var/www/html/*

What is my user account name? I put the bd user that i created with the tutorial “wordpressuser” but the terminal always say: chown: invalided user.

Thanks for helping.