From the Drupal backend:
- Configuration
- Account Settings
- Manage Fields
From here you can add your new field (Be sure to check the box that asks if this field should be present on user registration form)
Then you'll want to use a hook to disable this field in the user_profile
form.\
Code: template.php
function THEME_form_alter(&$form, &$form_state, $form_id) {
switch($form_id) {
case 'user_profile_form':
$form['field_my_field']['#disabled'] = true;
break;
}
}