Vagrant box for 16.04: https://atlas.hashicorp.com/ubuntu/boxes/xenial64
> sudo: unable to resolve host ubuntu-xenial
> mesg: ttyname failed: Inappropriate ioctl for device
I hope this PR (https://github.com/mitchellh/vagrant/pull/7241) gets merged because the private_network issue has been around since 15.04
I had better luck with https://atlas.hashicorp.com/gbarbieru/boxes/xenial which just got updated a few hours ago.
You can downgrade VirtualBox, dropping to 5.0.16 worked for me: http://download.virtualbox.org/virtualbox/5.0.16/