Comment 35 for bug 1561250

I can confirm this issue is also present when running on macOS.

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$ uname -a
Darwin 15.5.0 Darwin Kernel Version 15.5.0: Tue Apr 19 18:36:36 PDT 2016; root:xnu-3248.50.21~8/RELEASE_X86_64 x86_64

$ vagrant --version
Vagrant 1.8.4

$ vboxmanage --version
5.0.22r108108

$ vagrant box list | grep xenial
ubuntu/xenial64 (virtualbox, 20160615.1.0)

$ vagrant init ubuntu/xenial64

$ vagrant ssh

$ sudo cat /etc/hosts
sudo: unable to resolve host ubuntu-xenial
127.0.0.1 localhost

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
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Note the "sudo: unable to resolve host ubuntu-xenial" above.