ref https://www.vagrantup.com/docs/installation/
$ pacman -Syu virtualbox vagrant
$ brew cask install virtualbox vagrant
TODO
$ cd ubuntu-14.04
$ cp Vagrantfile.example Vagrantfile
$ wget -nc http://cloud-images.ubuntu.com/vagrant/trusty/current/trusty-server-cloudimg-amd64-vagrant-disk1.box
$ wget -nc https://github.com/mailhog/MailHog/releases/download/v0.2.0/MailHog_linux_amd64
$ vagrant up --no-provision
$ vagrant provision
$ open http://192.168.100.100:8025 #access mailhog web ui
$ open http://192.168.100.100:9000 #access graylog web ui, default username is 'admin', password is 'admin'.