Updated May 21/2018
There are lots of different how-tos out there for automatically launching VMs using VirtualBox on MacOS. Most of them focus on older versions of VirtualBox or old versions of MacOS.
Tested using MacOS High Sierra 10.13.4 running VirtualBox 5.2.12. The guest OS is Fedora 28.
Following the instructions on the VirtualBox website (https://www.virtualbox.org/manual/ch09.html#autostart), copy the Virtualbox autostart plist template file to your system's LaunchDaemons folder.
david$ sudo cp \