Hello, I'm installing Odoo 9  on a Ubuntu server 16.04. I'm following installation instructions from here: https://www.howtoforge.com/tutorial/install-odoo-erp-software-on-ubuntu-16-04/ When using this command: 
createuser --createdb --username postgres --no-createrole --no-superuser --pwprompt odoo
I get 
creation of new role failed: ERROR:  role "odoo" already exists  
How do I get past this? Do I have to make an additional user? 

Thx for the help