Aegir: perform custom tasks after a new site is installed

in a custom module, in a file called mysnippet.drush.inc (keep in mind that the install process is handled by drush...)

/**
 * Implementation of hook_post_hosting_TASK_TYPE_task().
 */
function mysnippet_post_hosting_install_task($task, $data) {
 
  if($task->options['profile']=='mycustomprofile') {
    $target = $task->context_options['uri'];
 
    //create local admin
    $dcmd =' user-create adminLocal --mail="admin@host.tld" --password="mypwd"';
    provision_backend_invoke($target, $dcmd);
  }
}

Display errors - WSOD

The bootstrap override the values you could set to display error ad the reporting level. To be 100% sure everything is printed out when something fails in a blank screen (wsod), make index.php like this:

Properly render a field

Drupal offers a few (sometimes complicated...) solutions to output a field. Lets take an example with a date field.
To display the full rendered field: field_view_field()