diff --git a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
index 3238ce6..e90cd0c 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
@@ -96,9 +96,10 @@ class ExtensionDiscovery {
    * @param string $root
    *   The app root.
    */
-  public function __construct($root) {
+  public function __construct($root, $use_file_cache = TRUE, $profile_directories = NULL) {
     $this->root = $root;
-    $this->fileCache = FileCacheFactory::get('extension_discovery');
+    $this->fileCache = $use_file_cache ? FileCacheFactory::get('extension_discovery') : NULL;
+    $this->profileDirectories = $profile_directories;
   }
 
   /**
@@ -427,7 +428,7 @@ protected function scanDirectory($dir, $include_tests) {
         continue;
       }
 
-      if ($cached_extension = $this->fileCache->get($fileinfo->getPathName())) {
+      if ($this->fileCache && $cached_extension = $this->fileCache->get($fileinfo->getPathName())) {
         $files[$cached_extension->getType()][$key] = $cached_extension;
         continue;
       }
@@ -467,7 +468,10 @@ protected function scanDirectory($dir, $include_tests) {
       $extension->origin = $dir;
 
       $files[$type][$key] = $extension;
-      $this->fileCache->set($fileinfo->getPathName(), $extension);
+
+      if ($this->fileCache) {
+        $this->fileCache->set($fileinfo->getPathName(), $extension);
+      }
     }
     return $files;
   }
diff --git a/core/modules/system/system.routing.yml b/core/modules/system/system.routing.yml
index a656ab3..3ec57c9 100644
--- a/core/modules/system/system.routing.yml
+++ b/core/modules/system/system.routing.yml
@@ -449,7 +449,7 @@ system.batch_page.json:
     _admin_route: TRUE
 
 system.db_update:
-  path: '/update.php/{op}'
+  path: '/admin/update/{op}'
   defaults:
     _title: 'Drupal database update'
     _controller: '\Drupal\system\Controller\DbUpdateController::handle'
diff --git a/core/update.php b/core/update.php
new file mode 100644
index 0000000..02ca5cc
--- /dev/null
+++ b/core/update.php
@@ -0,0 +1,127 @@
+<?php
+
+/**
+ * @file
+ * Provides a front controller dedicated to update which relies on as few as
+ * possible dependencies, so that it can change for example some of the really
+ * low level tables.
+ *
+ * @see \Drupal\system\Controller\DbUpdateController
+ */
+
+use Drupal\Core\Config\BootstrapConfigStorageFactory;
+use Drupal\Core\DrupalKernel;
+use Drupal\Core\Extension\Extension;
+use Drupal\Core\Extension\ExtensionDiscovery;
+use Drupal\Core\Site\Settings;
+use Drupal\Core\StreamWrapper\PublicStream;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
+
+/**
+ * Loads the update_early.inc file for a given extension.
+ *
+ * @param \Drupal\Core\Extension\Extension $module
+ */
+function _update_load_update_early_file(Extension $module) {
+  $filename = $module->getPath() . '/' . $module->getName() . '.update_early.inc';
+  if (file_exists($filename)) {
+    include_once $filename;
+  }
+}
+
+/**
+ * Gets all available update_early functions.
+ *
+ * @return string[]
+ */
+function _update_get_available_update_early_functions() {
+  $regexp = '/^(?<module>.+)_update_early_(?<version>\d+)$/';
+  $functions = get_defined_functions();
+
+  $updates = [];
+  foreach (preg_grep('/_\d+$/', $functions['user']) as $function) {
+    // If this function is a module update function, add it to the list of
+    // module updates.
+    if (preg_match($regexp, $function, $matches)) {
+      $updates[$matches['module']][] = $matches['version'];
+    }
+  }
+
+  // Ensure that updates are applied in numerical order.
+  foreach ($updates as &$module_updates) {
+    sort($module_updates, SORT_NUMERIC);
+  }
+
+  return $updates;
+}
+
+// Change the directory to the Drupal root.
+chdir('..');
+
+$autoloader = require_once __DIR__ . '/vendor/autoload.php';
+require_once __DIR__ . '/includes/utility.inc';
+
+$request = Request::createFromGlobals();
+// Manually resemble early bootstrap of DrupalKernel::boot().
+require_once __DIR__ . '/includes/bootstrap.inc';
+DrupalKernel::bootEnvironment();
+
+try {
+  Settings::initialize(dirname(__DIR__), DrupalKernel::findSitePath($request), $autoloader);
+
+  if (!Settings::get('update_free_access', FALSE)) {
+    throw new AccessDeniedHttpException();
+  }
+  else {
+    $kernel = new DrupalKernel('prod', $autoloader);
+    $kernel->setSitePath(DrupalKernel::findSitePath($request));
+
+    // We need a) the list of active modules (we get that from the config
+    // bootstrap factory) and b) the path to the modules, we use the extension
+    // discovery for that.
+
+    // Scan the module list.
+    // We don't support install profiles at that point?
+    $extension_discovery = new ExtensionDiscovery($kernel->getAppRoot(), FALSE, []);
+    $module_extensions = $extension_discovery->scan('module');
+
+    $config = BootstrapConfigStorageFactory::get();
+
+    // Load all the update_early.inc files.
+    foreach (array_keys($config->read('core.extension')['module']) as $module) {
+      if (isset($module_extensions[$module])) {
+        _update_load_update_early_file($module_extensions[$module]);
+      }
+    }
+
+    // First figure out which hook_update_early got executed already.
+    $filename = PublicStream::basePath() . '/.ht.update_early';
+    $existing_update_early_N = [];
+    if (file_exists($filename)) {
+      $existing_update_early_N = file_get_contents($filename);
+      $existing_update_early_N = explode("\n", $existing_update_early_N);
+    }
+
+    $available_update_early_N = _update_get_available_update_early_functions();
+    $not_executed_update_early_N = array_diff($available_update_early_N, $existing_update_early_N);
+
+    // Execute all of the remainign ones.
+    foreach ($available_update_early_N as $function) {
+      $output = $function();
+      $response->setContent($output)->prepare($request)->send();
+    }
+
+    // Redirect to the actual update controller.
+    $response = new RedirectResponse(str_replace('core/update.php', '', $request->getUriForPath('/admin/update')));
+    $response->prepare($request)->send();
+  }
+}
+catch (HttpExceptionInterface $e) {
+  $response = new Response('', $e->getStatusCode());
+  $response->prepare($request)->send();
+  exit;
+}