Headless Ubuntu Server 15.10 on Gigabyte GB-BXBT-2807

I had some trouble getting my Ubuntu Server 15.10 install on a Gigabyte GB-BXBT-2807 booting without the HDMI cable plugged in.

After some trial and error, I found an easy fix: edit the /etc/default/grub file (sudo nano /etc/default/grub) and modify / uncomment the following entries:

Regenerate the grub config: sudo update-grub2

After that Ubuntu Server just boots fine in headless mode without any HDMI cable plugged in.