Aegir: Switch Site Domains

siteswitch.drush.inc

<?php
// put in $aegirhome/.drush/siteswitch/
// run with: drush @hostmaster siteswitch "regexp" "replacepattern"
// example: drush @hostmaster siteswitch "(.*)\.yourdomain\.com" "\$1.yournewdomain.com"

function siteswitch_drush_command() {
  $commands = array();

  $commands['siteswitch'] = array(
    'description' => dt('Run siteswitch'),
    'arguments' => array('search' => 'Pattern to search for', 'replace' => 'Pattern to replace'),
  );

  return $commands;

  $nodes = db_query('SELECT nid, title FROM {node} WHERE type="site"');
  while ($site = db_fetch_array($nodes)) {
    if (preg_match('/' . $search . '/', $site['title'])) {
      $args = array(
        'new_uri' => preg_replace('/' . $search . '/', $replace, $site['title']),
        'new_db_server' => 2,
        'target_platform' => 79,
      );
      hosting_add_task($site['nid'], 'migrate', $args);
    }
  }
}

Target platform and db server is hardcoded, make sure you change that to suite your needs.