diff -u b/core/rebuild.php b/core/rebuild.php
--- b/core/rebuild.php
+++ b/core/rebuild.php
@@ -6,10 +6,10 @@
  *
  * Needs a token query argument which can be calculated using the
  * scripts/rebuild_token_calculator.sh script.
+ *
+ * @see drupal_rebuild()
  */
 
-use Drupal\Component\PhpStorage\PhpStorageFactory;
-use Drupal\Core\Cache\Cache;
 use Drupal\Component\Utility\Crypt;
 
 // Change the directory to the Drupal root.
@@ -23,22 +23,7 @@
     ((REQUEST_TIME - $_GET['timestamp']) < 300) &&
     ($_GET['token'] === Crypt::hmacBase64($_GET['timestamp'], $GLOBALS['drupal_hash_salt']))
   )) {
-  // drupal_bootstrap(DRUPAL_BOOTSTRAP_KERNEL) will build a new kernel. This
-  // comes before DRUPAL_BOOTSTRAP_PAGE_CACHE.
-  PhpStorageFactory::get('service_container')->deleteAll();
-  PhpStorageFactory::get('twig')->deleteAll();
-
-  // Disable the page cache.
-  drupal_page_is_cacheable(FALSE);
-
-  // Bootstrap up to where caches exist and clear them.
-  drupal_bootstrap(DRUPAL_BOOTSTRAP_PAGE_CACHE);
-  foreach (Cache::getBins() as $bin) {
-    $bin->deleteAll();
-  }
-
-  drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
-  drupal_flush_all_caches();
+  drupal_rebuild();
   drupal_set_message('Cache rebuild complete.');
 }
 
only in patch2:
unchanged:
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1,5 +1,6 @@
 <?php
 
+use Drupal\Component\PhpStorage\PhpStorageFactory;
 use Drupal\Component\Utility\Crypt;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\Settings;
@@ -7,6 +8,7 @@
 use Drupal\Component\Utility\Timer;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Component\Utility\Url;
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Database\Database;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
@@ -251,6 +253,32 @@ function timer_stop($name) {
 }
 
 /**
+ * Rebuilds all caches even when Drupal itself does not work.
+ *
+ * Requires DRUPAL_BOOTSTRAP_CONFIGURATION.
+ *
+ * @see rebuild.php
+ */
+function drupal_rebuild() {
+  // drupal_bootstrap(DRUPAL_BOOTSTRAP_KERNEL) will build a new kernel. This
+  // comes before DRUPAL_BOOTSTRAP_PAGE_CACHE.
+  PhpStorageFactory::get('service_container')->deleteAll();
+  PhpStorageFactory::get('twig')->deleteAll();
+
+  // Disable the page cache.
+  drupal_page_is_cacheable(FALSE);
+
+  // Bootstrap up to where caches exist and clear them.
+  drupal_bootstrap(DRUPAL_BOOTSTRAP_PAGE_CACHE);
+  foreach (Cache::getBins() as $bin) {
+    $bin->deleteAll();
+  }
+
+  drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
+  drupal_flush_all_caches();
+}
+
+/**
  * Returns the appropriate configuration directory.
  *
  * Returns the configuration path based on the site's hostname, port, and