Based on my answer to a StackOverflow question (which is itself based on the other answers).

Only tested on VirtualBox.

If you aren't using VirtualBox, or if you're fine with the default disk size of 10 GB:

• Skip the plugin installation.
• Remove the config.disksize... line from the Vagrantfile.

The keyboard layout is set to German. To change this, edit install-desktop.sh, and replace L='de' with your preferred keyboard layout language.

vagrant plugin install vagrant-disksize

vagrant up 2>&1 | tee log.txt
vagrant reload

After the reboot, the VM screen should show the LightDM login screen. Log in as user "ubuntu", password "ubuntu".

Re-running the provisioners:

# When VM is running:
vagrant provision 2>&1 | tee log.txt

# When VM is powered off:
vagrant up --provision 2>&1 | tee log.txt