I want to change the layout of add/edit page I have one content type called Restaurant, and I want to change the layout of this content type in the administrative area. When the administrator user adds/edits a Restaurant node, the layout should be my custom layout. 

How can I change the whole layout?
As shown in the comment at the beginning of theme_get_suggestions(), for a URL such as http://www.example.com/node/1/edit, the following default suggestions will be used.


page__node
page__node__%
page__node__1
page__node__edit


If you want to add page__node__edit__article as suggestion, you need to implement hook_preprocess_page() in a module. The following code works for any content type.

function mymodule_preprocess_page(&amp;$variables) {
  if (!empty($variables['node']) &amp;&amp; arg(2) == 'edit') {
    // (1)
    array_unshift($variables['theme_hook_suggestions'], 'page__node__edit__' . str_replace(array("/", "\\", "\0", '-'), array('', '', '', '_'), $variables['node']-&gt;type));
    // (1)
  }
}


If you want to be use not to apply the template file for, e.g., node/1/edit/revert, replace the code between // (1) with the following one.

$arg3 = arg(3);
if (empty($arg3)) {
  array_unshift($variables['theme_hook_suggestions'], 'page__node__edit__' . str_replace(array("/", "\\", "\0", '-'), array('', '', '', '_'), $variables['node']-&gt;type));
}