First find this line:
$form['path']['pathauto_perform_alias'] = array(
Then add:
'#value' => 1,
Source code viewer
'#type' => 'checkbox', '#value' => 1, '#title' => t('Automatic alias'), '#default_value' => $node->pathauto_perform_alias, '#description' => t('An alias will be generated for you. If you wish to create your own alias below, uncheck this option.'), '#weight' => -1, );Programming Language: PHP