getpassword error: Inappropriate ioctl for device vnc error
This error occurs most often because the configured user doesn't have a vncpasswd set. To fix this, as the user simply execute 'vncpasswd' and follow the prompts. It's just like passwd so you should already be familiar with it.
I was encountering the same problem. The issue for me was that I did not "su" to the user and re-type the passwords as shown in Step 3 of the following link.
Follow the instructions on the link below verbatim and you should be good to go.
http://tecadmin.net/setup-vnc-server-on-centos-redhat-and-fedora/
Hope this helps.