I had to figure out a few things to get Ubuntu installed and working well on VirtualBox.

I had to enable virtualization technologies in my BIOS. I have a Lenovo T520 and did this by pressing F1 during startup and then going to Security > Virtualization. If I did not do this then I would receive the error “VT-x features locked or unavailable in MSR” when trying to run with more than 1 CPU or 3584 MB of RAM.

The default disk is an 8GB dynamically expanding VDI. You may want to consider changing the default from 8GB to something more like 100GB. This is the max size only and will not be used unless needed.

Also, I had to run “sudo apt-get install dkms” to get the VirtualBox Guest Additions to work well.

Finally, I remapped the host key. By default all kinds of weird things happen when you use the right Ctrl button. This can be fixed by going to File > Preferences… > Input and then setting Host Key to something you never use like Pause.