Error While Installing ERPNext on Ubutu

Hi Everyone,
While installing ERPNext on an Ubuntu Machine.

sudo bash setup_frappe.sh --setup-production
Installing for Ubuntu vivid amd64
In case you encounter an error, you can post on https://discuss.frappe.io

Adding ubuntu mariadb repo
Installing packages for Ubuntu. This might take time…
Installing wkhtmltopdf
Installing wkhtmltox package for trusty (Ubuntu 14.4) even if you are using vivid.
–2016-02-24 11:49:51-- http://download.gna.org/wkhtmltopdf/0.12/0.12.2.1/wkhtmltox-0.12.2.1_linux-trusty-amd64.deb
Resolving download.gna.org (download.gna.org)… failed: No address associated with hostname.
wget: unable to resolve host address ‘download.gna.org

Any idea about it?

I just tested the gna.org site, and it is up and running. Sounds like an issue with your DNS server

how do u fix DNS Server issues?