Can anyone assist me in setting up a DNS server inside Ubuntu 15.04 server edition (inside VirtualBox)? This is on a private network in an area with absolutely no internet access, so I need to download everything from home and deploy/configure it at the remote site.
You will need to install bind9 bind9utils bind9-doc to install locally you need to make a private repository
Read the following articles https://help.ubuntu.com/community/Repositories/Personal and How to create a local APT repository? Follow the instructions and you should be good to go.
To learn more about BIND and how to configure you can refer to this link https://help.ubuntu.com/community/BIND9ServerHowto