Vagrant - Set Guest ENV vars

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

VAGRANT_API_VERSION='2'

$set_environment_variables = <<SCRIPT
cat > '/etc/profile.d/envvars.sh' <<EOV
# AWS environment variables.
export SOME_VAR=things
export OTHER_VAR='other stuff'
EOV
SCRIPT

Vagrant.configure(VAGRANT_API_VERSION) do |config|
  config.vm..box 'ubuntu/bionic64'
  
  # This method utilizes the variable file constructed in the `SCRIPT` above
  # which would be under source control as it is contained within this `Vagrantfile`
  config.vm.define 'my-host-name' do |machine|
    machine.vm.provision "shell", inline: $set_environment_variables, run: "always"
  end
  
  
  # This method utilizes a variable file which alreedy exists in the
  # codebase (although possibly not under source control). The `/vagrant` directory
  # on the guest machine maps to `.` on the host machine.
  config.vm.define 'my-host-name' do |machine|
    machine.vm.provision "shell", 
      inline: "echo 'source /vagrant/config/vagrant/bootstrap-env.sh' > /etc/profile.d/envvars.sh", 
      run: "always"
  end
end

This takes advantage of the /etc/profile mechanism which runs any script in /etc/profile.d/; this applies to all users on the system including root.