diff --git a/core/includes/common.inc b/core/includes/common.inc
index 0336161..a002e45 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3644,14 +3644,10 @@ function drupal_prepare_page($page) {
 
   // Modules can add elements to $page as needed in hook_page_build().
   if (!defined('MAINTENANCE_MODE')) {
-    $implementations = \Drupal::moduleHandler()->getImplementations('page_build');
-  }
-  else {
-    $implementations = array('system');
-  }
-  foreach ($implementations as $module) {
-    $function = $module . '_page_build';
-    $function($page);
+    foreach (\Drupal::moduleHandler()->getImplementations('page_build') as $module) {
+      $function = $module . '_page_build';
+      $function($page);
+    }
   }
   // Modules alter the $page as needed. Blocks are populated into regions like
   // 'sidebar_first', 'footer', etc.
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 7f494c5..de4069e 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -9,6 +9,7 @@
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\DatabaseExceptionWrapper;
 use Drupal\Core\Database\Install\TaskException;
+use Drupal\Core\Extension\InfoParser;
 use Drupal\Core\Installer\Exception\AlreadyInstalledException;
 use Drupal\Core\Installer\Exception\InstallerException;
 use Drupal\Core\Installer\Exception\NoProfilesException;
@@ -346,27 +347,47 @@ function install_begin_request(&$install_state) {
     }
   }
 
+  // Add list of all available profiles to the installation state.
+  $listing = new ExtensionDiscovery();
+  $listing->setProfileDirectories(array());
+  $install_state['profiles'] += $listing->scan('profile');
+
+  // Prime drupal_get_filename()'s static cache.
+  foreach ($install_state['profiles'] as $name => $profile) {
+    drupal_get_filename('profile', $name, $profile->uri);
+  }
+
+  $container->set('info_parser', new InfoParser());
+  if ($profile = _install_select_profile($install_state)) {
+    $install_state['parameters']['profile'] = $profile;
+    install_load_profile($install_state);
+    if (isset($install_state['profile_info']['distribution']['install']['theme'])) {
+      $install_state['theme'] = $install_state['profile_info']['distribution']['install']['theme'];
+    }
+  }
+
   // Replace services with in-memory and null implementations. This kernel is
   // replaced with a regular one in drupal_install_system().
   if (!$install_state['base_system_verified']) {
-    $environment = 'install';
     $GLOBALS['conf']['container_service_providers']['InstallerServiceProvider'] = 'Drupal\Core\Installer\InstallerServiceProvider';
-
-    // Various services need a database connection. Supply one.
-    if (!$install_state['database_verified']) {
-      Database::addConnectionInfo('install', 'default', array(
-        'driver' => 'sqlite',
-        'database' => ':memory:',
-      ));
-    }
+    $kernel = new DrupalKernel('install', drupal_classloader(), FALSE);
+    $module_list['system'] = 'core/modules/system/system.module';
+    $kernel->updateModules($module_list, $module_list);
   }
   else {
-    $environment = 'prod';
+    $kernel = new DrupalKernel('prod', drupal_classloader(), FALSE);
   }
-
-  $kernel = new DrupalKernel($environment, drupal_classloader(), FALSE);
   $kernel->boot();
 
+  // Override the module list with a minimal set of modules.
+  $module_handler = \Drupal::moduleHandler();
+  if ($profile && !$module_handler->moduleExists($profile)) {
+    $module_list = $module_handler->getModuleList();
+    $module_list[$profile] = $install_state['profiles'][$profile]->uri;
+    $module_handler->setModuleList($module_list);
+    $kernel->updateModules($module_list, $module_list);
+  }
+
   // Enter the request scope and add the Request.
   // @todo Remove this after converting all installer screens into controllers.
   $container = $kernel->getContainer();
@@ -389,40 +410,7 @@ function install_begin_request(&$install_state) {
     \Drupal::translation()->setDefaultLangcode($install_state['parameters']['langcode']);
   }
 
-  // Add list of all available profiles to the installation state.
-  $listing = new ExtensionDiscovery();
-  $listing->setProfileDirectories(array());
-  $install_state['profiles'] += $listing->scan('profile');
-
-  // Prime drupal_get_filename()'s static cache.
-  foreach ($install_state['profiles'] as $name => $profile) {
-    drupal_get_filename('profile', $name, $profile->uri);
-  }
-
-  if ($profile = _install_select_profile($install_state)) {
-    $install_state['parameters']['profile'] = $profile;
-    install_load_profile($install_state);
-    if (isset($install_state['profile_info']['distribution']['install']['theme'])) {
-      $install_state['theme'] = $install_state['profile_info']['distribution']['install']['theme'];
-    }
-  }
-
-  // Override the module list with a minimal set of modules.
-  $module_handler = \Drupal::moduleHandler();
-  $module_list = $module_handler->getModuleList();
-  if (!$module_handler->moduleExists('system')) {
-    $module_list['system'] = 'core/modules/system/system.module';
-    system_register('module', 'system', $module_list['system']);
-  }
-  if ($profile && !$module_handler->moduleExists($profile)) {
-    $module_list[$profile] = $install_state['profiles'][$profile]->uri;
-    system_register('profile', $profile, $module_list[$profile]);
-  }
-  $module_handler->setModuleList($module_list);
-  // After setting up a custom and finite module list in a custom low-level
-  // bootstrap like here, ensure to use ModuleHandler::loadAll() so that
-  // ModuleHandler::isLoaded() returns TRUE, since that is a condition being
-  // checked by other subsystems (e.g., the theme system).
+  // _theme() requires all modules to be loaded.
   $module_handler->loadAll();
 
   // Prepare for themed output. We need to run this at the beginning of the
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index ab2f37b..d1c13f9 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2085,10 +2085,12 @@ function template_preprocess_page(&$variables) {
   $variables['logo']              = theme_get_setting('logo.url');
   $variables['main_menu']         = theme_get_setting('features.main_menu') ? menu_main_menu() : array();
   $variables['secondary_menu']    = theme_get_setting('features.secondary_menu') ? menu_secondary_menu() : array();
-  $variables['action_links']      = menu_get_local_actions();
   $variables['site_name']         = (theme_get_setting('features.name') ? String::checkPlain($site_config->get('name')) : '');
   $variables['site_slogan']       = (theme_get_setting('features.slogan') ? filter_xss_admin($site_config->get('slogan')) : '');
-  $variables['tabs']              = menu_local_tabs();
+  if (!defined('MAINTENANCE_MODE')) {
+    $variables['tabs']              = menu_local_tabs();
+    $variables['action_links']      = menu_get_local_actions();
+  }
 
   // Pass the main menu and secondary menu to the template as render arrays.
   if (!empty($variables['main_menu'])) {
@@ -2129,10 +2131,12 @@ function template_preprocess_page(&$variables) {
   // re-use the cache of an already retrieved menu containing the active link
   // for the current page.
   // @see menu_tree_page_data()
-  $variables['breadcrumb'] = array(
-    '#theme' => 'breadcrumb',
-    '#breadcrumb' => \Drupal::service('breadcrumb')->build(\Drupal::request()->attributes->all()),
-  );
+  if (!defined('MAINTENANCE_MODE')) {
+    $variables['breadcrumb'] = array(
+      '#theme' => 'breadcrumb',
+      '#breadcrumb' => \Drupal::service('breadcrumb')->build(\Drupal::request()->attributes->all()),
+    );
+  }
 }
 
 /**
@@ -2223,7 +2227,6 @@ function template_preprocess_maintenance_page(&$variables) {
   $page_object = $variables['page']['#page'];
   $attributes = $page_object->getBodyAttributes();
   $classes = $attributes['class'];
-
   $classes[] = 'maintenance-page';
   $classes[] = 'in-maintenance';
   if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
@@ -2231,9 +2234,11 @@ function template_preprocess_maintenance_page(&$variables) {
   }
   $attributes['class'] = $classes;
 
+  // @see system_page_build()
   $attached = array(
     '#attached' => array(
       'library' => array(
+        'core/normalize',
         'system/maintenance',
       ),
     ),
@@ -2246,16 +2251,11 @@ function template_preprocess_maintenance_page(&$variables) {
  *
  * Default template: install-page.html.twig.
  *
- * The variables array generated here is a mirror of
- * template_preprocess_page(). This preprocessor will run its course when
- * theme_install_page() is invoked.
- *
  * @param array $variables
  *   An associative array containing:
  *   - content - An array of page content.
  *
  * @see template_preprocess_maintenance_page()
- *
  */
 function template_preprocess_install_page(&$variables) {
   template_preprocess_maintenance_page($variables);
@@ -2263,9 +2263,7 @@ function template_preprocess_install_page(&$variables) {
   $page_object = $variables['page']['#page'];
   $attributes = $page_object->getBodyAttributes();
   $classes = $attributes['class'];
-
   $classes[] = 'install-page';
-
   $attributes['class'] = $classes;
 
   // Override the site name that is displayed on the page, since Drupal is
diff --git a/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php b/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
index 26b1d7d..c96d287 100644
--- a/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
+++ b/core/lib/Drupal/Core/Installer/InstallerServiceProvider.php
@@ -67,8 +67,6 @@ public function alter(ContainerBuilder $container) {
     // throws an exception upon trying to load a non-existing file.
     $container->get('config.factory')->setOverrideState(FALSE);
 
-    $container->set('database', Database::getConnection('default', 'install'));
-
     // No service may persist when the early installer kernel is rebooted into
     // the production environment.
     // @todo The DrupalKernel reboot performed by drupal_install_system() is