code: function getUserdata0_(username, upNamespace, envVars_, origUsername) {
    var envVars = cleanEnvVars(upNamespace, envVars_);
  
    var script  = [
                  "#!/bin/bash -ex",
           format("if ! [ -d /home/%s ]; then", username),
           format("  usermod -l %s %s", username, origUsername),
           format("  groupmod -n %s %s", username, origUsername),
           format("  usermod  -d /home/%s -m %s", username, username),
                  "fi",
  
           format("if [ -f /etc/sudoers.d/90-cloudimg-%s ]; then", origUsername),
           format("  mv /etc/sudoers.d/90-cloudimg-%s /etc/sudoers.d/90-cloud-init-users", origUsername),
                  "fi",
           format("perl -pi -e 's/%s/%s/g;' /etc/sudoers.d/90-cloud-init-users", origUsername, username),
  
                  "if ! grep `hostname` /etc/hosts; then",
                  "  echo \"127.0.0.1 `hostname`\" | sudo tee -a /etc/hosts",
                  "fi",
                  ""
    ];
    _.each(envVars, function(value, key) {
      script.push("echo "+key+"="+value+" | sudo tee -a /etc/environment");
    });
    script.push(  "");
  
    console.error(script);
    return script;
  }
docs: The userdata for when starting an instance from a base-image.
  
  Basically, it renames the default 'ubuntu' user to 'scotty'; manages
  /etc/hosts, and sets a couple of system-wide env vars.