Vagrant's Ubuntu 16.04 vagrantfile default password

^{As of writing this answer: no one ever publicly shared the password for user ubuntu on ubuntu/xenial64 Vagrant box (see #1569237).}

It's not necessary. You can:

• login using SSH key authentication
• change the password using sudo passwd ubuntu (by default ubuntu user has sudo-permissions with NOPASSWD set)

Actually, not only you can, but you should change the password.

The password is located in the ~/.vagrant.d/ubuntu-VAGRANTSLASH-xenial64/20161221.0.0/virtualbox/Vagrantfile as mention by user @prometee in this launchpad discussion #1569237.

Here is mine (line 8):

# Front load the includes
include_vagrantfile = File.expand_path("../include/_Vagrantfile", __FILE__)
load include_vagrantfile if File.exist?(include_vagrantfile)

Vagrant.configure("2") do |config|
  config.vm.base_mac = "022999D56C03"
  config.ssh.username = "ubuntu"
  config.ssh.password = "fbcd1ed4fe8c83b157dc6e0f"

  config.vm.provider "virtualbox" do |vb|
     vb.customize [ "modifyvm", :id, "--uart1", "0x3F8", "4" ]
     vb.customize [ "modifyvm", :id, "--uartmode1", "file", File.join(Dir.pwd, "ubuntu-xenial-16.04-cloudimg-console.log") ]
  end
end

FYI, user @racb mention in the same discusison that the this bug report having been filed to ubuntu and so far no [...] decision has been made yet about it.

The default user and password is:

user: vagrant password: vagrant