diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index e1ae91a..325e7c3 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -612,4 +612,14 @@ public static function formBuilder() {
     return static::$container->get('form_builder');
   }
 
+  /**
+   * Gets the syncing state.
+   *
+   * @return bool
+   *   Returns TRUE is syncing flag set.
+   */
+  public function isConfigSyncing() {
+    return static::$container->get('config.installer')->isSyncing();
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Config/BatchConfigImporter.php b/core/lib/Drupal/Core/Config/BatchConfigImporter.php
index 0ab6cc1..ba33dcf 100644
--- a/core/lib/Drupal/Core/Config/BatchConfigImporter.php
+++ b/core/lib/Drupal/Core/Config/BatchConfigImporter.php
@@ -26,6 +26,10 @@ public function initialize() {
       throw new ConfigImporterException(sprintf('%s is already importing', static::LOCK_ID));
     }
     $this->totalToProcess = 0;
+
+    // @todo batch this properly.
+    $this->handleExtensions();
+
     foreach(array('create', 'delete', 'update') as $op) {
       $this->totalToProcess += count($this->getUnprocessed($op));
     }
diff --git a/core/lib/Drupal/Core/Config/ConfigImporter.php b/core/lib/Drupal/Core/Config/ConfigImporter.php
index 24d5e71..de1570c 100644
--- a/core/lib/Drupal/Core/Config/ConfigImporter.php
+++ b/core/lib/Drupal/Core/Config/ConfigImporter.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\Config;
 
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Extension\ThemeHandlerInterface;
 use Drupal\Component\Utility\String;
 use Drupal\Core\Config\Entity\ImportableEntityStorageInterface;
 use Drupal\Core\DependencyInjection\DependencySerialization;
@@ -71,7 +73,7 @@ class ConfigImporter extends DependencySerialization {
   /**
    * The typed config manager.
    *
-   * @var \Drupal\Core\Config\TypedConfigManager
+   * @var \Drupal\Core\Config\TypedConfigManagerInterface
    */
   protected $typedConfigManager;
 
@@ -90,6 +92,20 @@ class ConfigImporter extends DependencySerialization {
   protected $validated;
 
   /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * The theme handler.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $themeHandler;
+
+  /**
    * Constructs a configuration import object.
    *
    * @param \Drupal\Core\Config\StorageComparerInterface $storage_comparer
@@ -103,13 +119,19 @@ class ConfigImporter extends DependencySerialization {
    *   The lock backend to ensure multiple imports do not occur at the same time.
    * @param \Drupal\Core\Config\TypedConfigManager $typed_config
    *   The typed configuration manager.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler
+   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
+   *   The theme handler
    */
-  public function __construct(StorageComparerInterface $storage_comparer, EventDispatcherInterface $event_dispatcher, ConfigManagerInterface $config_manager, LockBackendInterface $lock, TypedConfigManager $typed_config) {
+  public function __construct(StorageComparerInterface $storage_comparer, EventDispatcherInterface $event_dispatcher, ConfigManagerInterface $config_manager, LockBackendInterface $lock, TypedConfigManagerInterface $typed_config, ModuleHandlerInterface $module_handler, ThemeHandlerInterface $theme_handler) {
     $this->storageComparer = $storage_comparer;
     $this->eventDispatcher = $event_dispatcher;
     $this->configManager = $config_manager;
     $this->lock = $lock;
     $this->typedConfigManager = $typed_config;
+    $this->moduleHandler = $module_handler;
+    $this->themeHandler = $theme_handler;
     $this->processed = $this->storageComparer->getEmptyChangelist();
   }
 
@@ -208,6 +230,10 @@ public function import() {
         // Another process is synchronizing configuration.
         throw new ConfigImporterException(sprintf('%s is already importing', static::LOCK_ID));
       }
+
+      // Where to put this?
+      $this->handleExtensions();
+
       // First pass deleted, then new, and lastly changed configuration, in order
       // to handle dependencies correctly.
       // @todo Implement proper dependency ordering using
@@ -341,4 +367,126 @@ public function alreadyImporting() {
     return !$this->lock->lockMayBeAvailable(static::LOCK_ID);
   }
 
+  /**
+   * Returns the identifier for events and locks.
+   *
+   * @return string
+   *   The identifier for events and locks.
+   */
+  public function getId() {
+    return static::LOCK_ID;
+  }
+
+  /**
+   * Checks if a configuration object will be updated by the import.
+   *
+   * @param $config_name
+   *   The configuration object name.
+   *
+   * @return bool
+   *   TRUE if the configuration object will be updated.
+   */
+  protected function hasUpdate($config_name) {
+    return in_array($config_name, $this->getUnprocessed('update'));
+  }
+
+  /**
+   * Handle changes to installed modules and themes.
+   */
+  protected function handleExtensions() {
+    // Are there changes to process?
+    $module_update = $this->hasUpdate('system.module');
+    $theme_update = $this->hasUpdate('system.theme');
+    if ($module_update || $theme_update) {
+      // Set the config installer to use the staging directory instead of the
+      // extensions own default config directories.
+      \Drupal::service('config.installer')
+        ->setSyncing(TRUE)
+        ->setSourceStorage($this->storageComparer->getSourceStorage());
+
+      if ($module_update) {
+        $this->handleModules();
+      }
+
+      if ($theme_update) {
+        $this->handleThemes();
+      }
+
+      \Drupal::service('config.installer')
+        ->setSyncing(FALSE)
+        ->resetSourceStorage();
+
+      // Recalculate differences as default config could have been imported.
+      $this->storageComparer->reset();
+      $this->processed = $this->storageComparer->getEmptyChangelist();
+      drupal_flush_all_caches();
+      // Modules have been updated. Services etc might have changed.
+      // We don't reinject storage comparer because swapping out the active
+      // store during config import is a complete nonsense.
+      $this->reInjectMe();
+
+    }
+  }
+
+  /**
+   * Install or uninstall modules depending on configuration to import.
+   */
+  protected function handleModules() {
+    $current = $this->storageComparer->getTargetStorage()->read('system.module');
+    $new = $this->storageComparer->getSourceStorage()->read('system.module');
+
+    $to_enable = array_diff(array_keys($new['enabled']), array_keys($current['enabled']));
+    if (!$this->moduleHandler->install($to_enable)) {
+      throw new ConfigImporterException(sprintf('Unable to enable modules'));
+    }
+
+    $to_uninstall = array_diff(array_keys($current['enabled']), array_keys($new['enabled']));
+    if (!$this->moduleHandler->uninstall($to_uninstall)) {
+       throw new ConfigImporterException(sprintf('Unable to uninstall modules'));
+    }
+  }
+
+  /**
+   * Enable or disable themes depending on configuration to import.
+   */
+  protected function handleThemes() {
+    $current = $this->storageComparer->getTargetStorage()->read('system.theme');
+    $new = $this->storageComparer->getSourceStorage()->read('system.theme');
+
+    $enabled = isset($current['enabled']) ? $current['enabled'] : array();
+
+    $themes_to_enable = array_diff(array_keys($new['enabled']), array_keys($enabled));
+    $themes_to_disable = array_diff(array_keys($enabled), array_keys($new['enabled']));
+
+    if (!empty($themes_to_enable)) {
+      $this->themeHandler->enable($themes_to_enable);
+    }
+
+    // Are we disabling the default theme? This is not possible. Update the
+    // value to the value from the staged configuration. Enabling themes first
+    // ensures that if any of the newly enabled themes are the default theme it
+    // will be already enabled.
+    if(in_array($current['default'], $themes_to_disable)) {
+      // Use the configuration factory to write the data since system.theme
+      // might have been updated by enabling themes.
+      $this->configManager->getConfigFactory()
+        ->get('system.theme')
+        ->set('default', $new['default'])
+        ->save();
+    }
+
+    if (!empty($themes_to_disable)) {
+      $this->themeHandler->disable($themes_to_disable);
+    }
+  }
+
+  protected function reInjectMe() {
+    $this->eventDispatcher = \Drupal::service('event_dispatcher');
+    $this->configFactory = \Drupal::configFactory();
+    $this->entityManager = \Drupal::entityManager();
+    $this->lock = \Drupal::lock();
+    $this->typedConfigManager = \Drupal::service('config.typed');
+    $this->moduleHandler = \Drupal::moduleHandler();
+    $this->themeHandler = \Drupal::service('theme_handler');
+  }
 }
diff --git a/core/lib/Drupal/Core/Config/ConfigInstaller.php b/core/lib/Drupal/Core/Config/ConfigInstaller.php
index b039b8f..8da1930 100644
--- a/core/lib/Drupal/Core/Config/ConfigInstaller.php
+++ b/core/lib/Drupal/Core/Config/ConfigInstaller.php
@@ -49,6 +49,20 @@ class ConfigInstaller implements ConfigInstallerInterface {
   protected $eventDispatcher;
 
   /**
+   * The configuration storage that provides the default configuration.
+   *
+   * @var \Drupal\Core\Config\StorageInterface
+   */
+  protected $sourceStorage;
+
+  /**
+   * Is configuration being created as part of a configuration sync.
+   *
+   * @var bool
+   */
+  protected $isSyncing = FALSE;
+
+  /**
    * Constructs the configuration installer.
    *
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
@@ -75,7 +89,7 @@ public function __construct(ConfigFactoryInterface $config_factory, StorageInter
    */
   public function installDefaultConfig($type, $name) {
     // Get all default configuration owned by this extension.
-    $source_storage = new ExtensionInstallStorage($this->activeStorage);
+    $source_storage = $this->getSourceStorage();
     $config_to_install = $source_storage->listAll($name . '.');
 
     // Work out if this extension provides default configuration for any other
@@ -125,6 +139,18 @@ public function installDefaultConfig($type, $name) {
           $new_config->setData($data[$name]);
         }
         if ($entity_type = $this->configManager->getEntityTypeIdByName($name)) {
+
+          // If we are syncing do not create configuration entities. Pluggable
+          // configuration entities can have dependencies on modules that are
+          // not yet enabled. In the absence of dependency management for config
+          // entities this is a good as we can do. The problem with this
+          // approach is that any code that expects default configuration
+          // entities to exist (even if there is code the prevents this from
+          // happening) will be unstable after the module has been enabled and
+          // before the config entity has been imported.
+          if ($this->isSyncing) {
+            continue;
+          }
           $entity_storage = $this->configManager
             ->getEntityManager()
             ->getStorageController($entity_type);
@@ -133,6 +159,9 @@ public function installDefaultConfig($type, $name) {
           if ($this->activeStorage->exists($name)) {
             $id = $entity_storage->getIDFromConfigName($name, $entity_storage->getEntityType()->getConfigPrefix());
             $entity = $entity_storage->load($id);
+            if ($this->isSyncing) {
+              $entity->setSyncing(TRUE);
+            }
             foreach ($new_config->get() as $property => $value) {
               $entity->set($property, $value);
             }
@@ -154,4 +183,48 @@ public function installDefaultConfig($type, $name) {
     $this->configFactory->reset();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function setSourceStorage(StorageInterface $storage) {
+    $this->sourceStorage = $storage;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function resetSourceStorage() {
+    $this->sourceStorage = null;
+    return $this;
+  }
+
+  /**
+   * Gets the configuration storage that provides the default configuration.
+   *
+   * @return \Drupal\Core\Config\StorageInterface
+   *   The configuration storage that provides the default configuration.
+   */
+  public function getSourceStorage() {
+    if (!isset($this->sourceStorage)) {
+      // If using the the extension install storage class can not
+      $this->sourceStorage = new ExtensionInstallStorage($this->activeStorage);
+    }
+    return $this->sourceStorage;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setSyncing($status) {
+    $this->isSyncing = $status;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isSyncing() {
+    return $this->isSyncing;
+  }
 }
diff --git a/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php b/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
index 927c610..6e7c20d 100644
--- a/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
+++ b/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
@@ -37,4 +37,38 @@
    */
   public function installDefaultConfig($type, $name);
 
+  /**
+   * Sets the configuration storage that provides the default configuration.
+   *
+   * @param \Drupal\Core\Config\StorageInterface $storage
+   *
+   * @return self
+   *   The configuration installer.
+   */
+  public function setSourceStorage(StorageInterface $storage);
+
+  /**
+   * Resets the configuration storage that provides the default configuration.
+   *
+   * @return self
+   *   The configuration installer.
+   */
+  public function resetSourceStorage();
+
+  /**
+   * Sets the status of the isSyncing flag.
+   *
+   * @param bool $status
+   *   The status of the sync flag.
+   */
+  public function setSyncing($status);
+
+  /**
+   * Gets the syncing state.
+   *
+   * @return bool
+   *   Returns TRUE is syncing flag set.
+   */
+  public function isSyncing();
+
 }
diff --git a/core/lib/Drupal/Core/Config/ConfigManager.php b/core/lib/Drupal/Core/Config/ConfigManager.php
index 418b912..3561924 100644
--- a/core/lib/Drupal/Core/Config/ConfigManager.php
+++ b/core/lib/Drupal/Core/Config/ConfigManager.php
@@ -93,6 +93,13 @@ public function getEntityManager() {
   /**
    * {@inheritdoc}
    */
+  public function getConfigFactory() {
+    return $this->configFactory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function diff(StorageInterface $source_storage, StorageInterface $target_storage, $name) {
     // @todo Replace with code that can be autoloaded.
     //   https://drupal.org/node/1848266
diff --git a/core/lib/Drupal/Core/Config/ConfigManagerInterface.php b/core/lib/Drupal/Core/Config/ConfigManagerInterface.php
index b5084fe..4da9474 100644
--- a/core/lib/Drupal/Core/Config/ConfigManagerInterface.php
+++ b/core/lib/Drupal/Core/Config/ConfigManagerInterface.php
@@ -32,6 +32,14 @@ public function getEntityTypeIdByName($name);
   public function getEntityManager();
 
   /**
+   * Gets the config factory.
+   *
+   * @return \Drupal\Core\Config\ConfigFactoryInterface
+   *   The entity manager.
+   */
+  public function getConfigFactory();
+
+  /**
    * Return a formatted diff of a named config between two storages.
    *
    * @param \Drupal\Core\Config\StorageInterface $source_storage
diff --git a/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
index a20b9b9..e0807e5 100644
--- a/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -582,6 +582,12 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
     // Required for module installation checks.
     include_once DRUPAL_ROOT . '/core/includes/install.inc';
 
+    /** @var \Drupal\Core\Config\ConfigInstaller $config_installer */
+    $config_installer = \Drupal::service('config.installer');
+    $sync_status = $config_installer->isSyncing();
+    if ($sync_status) {
+      $source_storage = $config_installer->getSourceStorage();
+    }
     $modules_installed = array();
     foreach ($module_list as $module) {
       $enabled = $module_config->get("enabled.$module") !== NULL;
@@ -671,6 +677,18 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
         }
 
         // Install default configuration of the module.
+        $config_installer = \Drupal::service('config.installer');
+        if ($sync_status) {
+          $config_installer
+            ->setSyncing(TRUE)
+            ->setSourceStorage($source_storage);
+        }
+        else {
+          // If we're not in a config synchronisation reset the source storage
+          // so that the extension install storage will pick up the new
+          // configuration.
+          $config_installer->resetSourceStorage();
+        }
         \Drupal::service('config.installer')->installDefaultConfig('module', $module);
 
         // If the module has no current updates, but has some that were
@@ -732,7 +750,7 @@ public function uninstall(array $module_list, $uninstall_dependents = TRUE) {
 
           // Skip already uninstalled modules.
           if (isset($installed_modules[$dependent]) && !isset($module_list[$dependent]) && $dependent != $profile) {
-            $module_list[$dependent] = TRUE;
+            $module_list[$dependent] = $dependent;
           }
         }
       }
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index db22e5f..c4218a4 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -145,6 +145,11 @@ public function enable(array $theme_list) {
       // Refresh the theme list as installation of default configuration needs
       // an updated list to work.
       $this->reset();
+      // If we're not in a config synchronisation reset the source storage so
+      // that the extension install storage will pick up the new configuration.
+      if (!$this->configInstaller->isSyncing()) {
+        $this->configInstaller->resetSourceStorage();
+      }
       // Install default configuration of the theme.
       $this->configInstaller->installDefaultConfig('theme', $key);
     }
diff --git a/core/modules/aggregator/config/views.view.aggregator_rss_feed.yml b/core/modules/aggregator/config/views.view.aggregator_rss_feed.yml
index d22fdcb..c4caa75 100644
--- a/core/modules/aggregator/config/views.view.aggregator_rss_feed.yml
+++ b/core/modules/aggregator/config/views.view.aggregator_rss_feed.yml
@@ -8,7 +8,7 @@ display:
     display_plugin: default
     id: default
     display_title: Master
-    position: 1
+    position: 0
     display_options:
       access:
         type: none
@@ -137,7 +137,7 @@ display:
     display_plugin: feed
     id: feed_items
     display_title: Feed
-    position: 2
+    position: 1
     display_options:
       path: aggregator/rss
       display_description: ''
diff --git a/core/modules/comment/config/views.view.comments_recent.yml b/core/modules/comment/config/views.view.comments_recent.yml
index 15993f8..204ef53 100644
--- a/core/modules/comment/config/views.view.comments_recent.yml
+++ b/core/modules/comment/config/views.view.comments_recent.yml
@@ -4,19 +4,11 @@ core: 8.x
 description: 'Recent comments.'
 status: true
 display:
-  block_1:
-    display_plugin: block
-    id: block_1
-    display_title: Block
-    position: 0
-    display_options:
-      block_description: 'Recent comments'
-      block_category: 'Lists (Views)'
   default:
     display_plugin: default
     id: default
     display_title: Master
-    position: 1
+    position: 0
     display_options:
       access:
         type: perm
@@ -229,6 +221,14 @@ display:
           content: 'No comments available.'
           tokenize: false
           plugin_id: text_custom
+  block_1:
+    display_plugin: block
+    id: block_1
+    display_title: Block
+    position: 1
+    display_options:
+      block_description: 'Recent comments'
+      block_category: 'Lists (Views)'
 label: 'Recent comments'
 module: views
 id: comments_recent
diff --git a/core/modules/comment/lib/Drupal/comment/CommentManager.php b/core/modules/comment/lib/Drupal/comment/CommentManager.php
index 6976e42..21f8874 100644
--- a/core/modules/comment/lib/Drupal/comment/CommentManager.php
+++ b/core/modules/comment/lib/Drupal/comment/CommentManager.php
@@ -184,6 +184,14 @@ public function addDefaultField($entity_type, $bundle, $field_name = 'comment',
         ))
         ->save();
 
+      // The comment field should be hidden in all other form displays.
+      foreach ($this->entityManager->getFormModes($entity_type) as $id => $form_mode) {
+        $display = entity_get_form_display($entity_type, $bundle, $id);
+        // Only update existing displays.
+        if ($display && !$display->isNew()) {
+          $display->removeComponent($field_name)->save();
+        }
+      }
       // Set default to display comment list.
       entity_get_display($entity_type, $bundle, 'default')
         ->setComponent($field_name, array(
@@ -192,6 +200,15 @@ public function addDefaultField($entity_type, $bundle, $field_name = 'comment',
           'weight' => 20,
         ))
         ->save();
+        // The comment field should be hidden in all other view displays.
+      foreach ($this->entityManager->getViewModes($entity_type) as $id => $view_mode) {
+        $display = entity_get_display($entity_type, $bundle, $id);
+        // Only update existing displays.
+        if ($display && !$display->isNew()) {
+          $display->removeComponent($field_name)->save();
+        }
+      }
+
     }
     $this->addBodyField($entity_type, $field_name);
   }
diff --git a/core/modules/config/lib/Drupal/config/Form/ConfigSync.php b/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
index c600001..8ae2b63 100644
--- a/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
+++ b/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
@@ -7,6 +7,10 @@
 
 namespace Drupal\config\Form;
 
+use Drupal\Component\Uuid\UuidInterface;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Extension\ThemeHandlerInterface;
 use Drupal\Core\Config\ConfigManagerInterface;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Config\StorageInterface;
@@ -73,6 +77,20 @@ class ConfigSync extends FormBase {
   protected $typedConfigManager;
 
   /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * The theme handler.
+   *
+   * @var \Drupal\Core\Extension\ThemeHandlerInterface
+   */
+  protected $themeHandler;
+
+  /**
    * Constructs the object.
    *
    * @param \Drupal\Core\Config\StorageInterface $sourceStorage
@@ -89,8 +107,12 @@ class ConfigSync extends FormBase {
    *   The url generator service.
    * @param \Drupal\Core\Config\TypedConfigManager $typed_config
    *   The typed configuration manager.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler
+   * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
+   *   The theme handler
    */
-  public function __construct(StorageInterface $sourceStorage, StorageInterface $targetStorage, LockBackendInterface $lock, EventDispatcherInterface $event_dispatcher, ConfigManagerInterface $config_manager, UrlGeneratorInterface $url_generator, TypedConfigManager $typed_config) {
+  public function __construct(StorageInterface $sourceStorage, StorageInterface $targetStorage, LockBackendInterface $lock, EventDispatcherInterface $event_dispatcher, ConfigManagerInterface $config_manager, UrlGeneratorInterface $url_generator, TypedConfigManager $typed_config, ModuleHandlerInterface $module_handler, ThemeHandlerInterface $theme_handler) {
     $this->sourceStorage = $sourceStorage;
     $this->targetStorage = $targetStorage;
     $this->lock = $lock;
@@ -98,6 +120,8 @@ public function __construct(StorageInterface $sourceStorage, StorageInterface $t
     $this->configManager = $config_manager;
     $this->urlGenerator = $url_generator;
     $this->typedConfigManager = $typed_config;
+    $this->moduleHandler = $module_handler;
+    $this->themeHandler = $theme_handler;
   }
 
   /**
@@ -111,7 +135,9 @@ public static function create(ContainerInterface $container) {
       $container->get('event_dispatcher'),
       $container->get('config.manager'),
       $container->get('url_generator'),
-      $container->get('config.typed')
+      $container->get('config.typed'),
+      $container->get('module_handler'),
+      $container->get('theme_handler')
     );
   }
 
@@ -222,7 +248,9 @@ public function submitForm(array &$form, array &$form_state) {
       $this->eventDispatcher,
       $this->configManager,
       $this->lock,
-      $this->typedConfigManager
+      $this->typedConfigManager,
+      $this->moduleHandler,
+      $this->themeHandler
     );
     if ($config_importer->alreadyImporting()) {
       drupal_set_message($this->t('Another request may be synchronizing configuration already.'));
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportAllTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportAllTest.php
new file mode 100644
index 0000000..9f7f707
--- /dev/null
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportAllTest.php
@@ -0,0 +1,109 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\config\Tests\ConfigImportAllTest.
+ */
+
+namespace Drupal\config\Tests;
+
+use Drupal\Core\Config\StorageComparer;
+use Drupal\system\Tests\Module\ModuleTestBase;
+
+class ConfigImportAllTest extends ModuleTestBase {
+
+  /**
+   * The profile to install as a basis for testing.
+   *
+   * Using the standard profile as this has a lot of additional configuration.
+   *
+   * @var string
+   */
+  protected $profile = 'standard';
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Install/uninstall modules',
+      'description' => 'Install/uninstall core module and confirm table creation/deletion.',
+      'group' => 'Module',
+    );
+  }
+
+  /**
+   * Tests that a fixed set of modules can be installed and uninstalled.
+   */
+  public function testInstallUninstall() {
+
+    // Get a list of modules to enable.
+    $all_modules = system_rebuild_module_data();
+    $all_modules = array_filter($all_modules, function ($module) {
+      // Filter hidden, already enabled modules and modules in the Testing
+      // package.
+      if (!empty($module->info['hidden']) || $module->status == TRUE || $module->info['package'] == 'Testing') {
+        return FALSE;
+      }
+      return TRUE;
+    });
+
+    // Install every module possible.
+    \Drupal::moduleHandler()->install(array_keys($all_modules));
+
+    $this->assertModules(array_keys($all_modules), TRUE);
+    foreach($all_modules as $module => $info) {
+      $this->assertModuleConfig($module);
+      $this->assertModuleTablesExist($module);
+    }
+
+    // Export active config to staging
+    $this->copyConfig($this->container->get('config.storage'), $this->container->get('config.storage.staging'));
+
+    system_list_reset();
+    $this->resetAll();
+
+    // Delete every field on the site so all modules can be disabled. For
+    // example, if a comment field exists then module becomes required and can
+    // not be uninstalled.
+    $fields = \Drupal::service('field.info')->getFields();
+    foreach ($fields as $field) {
+      entity_invoke_bundle_hook('delete', $field->entity_type, $field->entity_type . '__' . $field->name);
+      $field->delete();
+    }
+    // Purge the data.
+    field_purge_batch(1000);
+
+    system_list_reset();
+    $all_modules = system_rebuild_module_data();
+    $all_modules = array_filter($all_modules, function ($module) {
+      // Filter required and not enabled modules.
+      if (!empty($module->info['required']) || $module->status == FALSE) {
+        return FALSE;
+      }
+      return TRUE;
+    });
+
+    $this->assertTrue(isset($all_modules['comment']), 'The comment module will be disabled');
+
+    \Drupal::moduleHandler()->uninstall(array_keys($all_modules));
+
+    $this->assertModules(array_keys($all_modules), FALSE);
+    foreach($all_modules as $module => $info) {
+      $this->assertNoModuleConfig($module);
+      $this->assertModuleTablesDoNotExist($module);
+    }
+
+    $this->configImporter()->import();
+
+    $this->assertModules(array_keys($all_modules), TRUE);
+    foreach($all_modules as $module => $info) {
+      $this->assertModuleConfig($module);
+      $this->assertModuleTablesExist($module);
+    }
+
+    // Ensure that we have no configuration changes to import.
+    $storage_comparer = new StorageComparer(
+      $this->container->get('config.storage.staging'),
+      $this->container->get('config.storage')
+    );
+    $this->assertIdentical($storage_comparer->createChangelist()->getChangelist(), $storage_comparer->getEmptyChangelist());
+  }
+}
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
index 51f9182..d2eb827 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImportUITest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\config\Tests;
 
+use Drupal\Core\Config\InstallStorage;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -14,7 +15,7 @@
  */
 class ConfigImportUITest extends WebTestBase {
 
-  public static $modules = array('config', 'config_test');
+  public static $modules = array('config', 'config_test', 'config_import_test');
 
   public static function getInfo() {
     return array(
@@ -38,6 +39,7 @@ function setUp() {
   function testImport() {
     $name = 'system.site';
     $dynamic_name = 'config_test.dynamic.new';
+    /** @var \Drupal\Core\Config\StorageInterface $staging */
     $staging = $this->container->get('config.storage.staging');
 
     $this->drupalGet('admin/config/development/configuration');
@@ -65,16 +67,50 @@ function testImport() {
     $staging->write($dynamic_name, $original_dynamic_data);
     $this->assertIdentical($staging->exists($dynamic_name), TRUE, $dynamic_name . ' found.');
 
+    // Enable the Ban and Action modules during import. The Ban module is used
+    // because it creates a table during the install. The Action module is used
+    // because it creates a single simple configuration file during the install.
+    $system_module = \Drupal::config('system.module')->get();
+    $system_module['enabled']['action'] = 0;
+    $system_module['enabled']['ban'] = 0;
+    $system_module['enabled'] = module_config_sort($system_module['enabled']);
+    $staging->write('system.module', $system_module);
+
+    // Use the install storage so that we can read configuration from modules
+    // and themes that are not installed.
+    $install_storage = new InstallStorage();
+
+    // Enable the bartik theme and set it as default.
+    $system_theme = \Drupal::config('system.theme')->get();
+    $system_theme['enabled']['bartik'] = 0;
+    $system_theme['default'] = 'bartik';
+    $staging->write('system.theme', $system_theme);
+    $staging->write('bartik.settings', $install_storage->read('bartik.settings'));
+
+    // Read the action config from module default config folder.
+    $action_settings = $install_storage->read('action.settings');
+    $action_settings['recursion_limit'] = 50;
+    $staging->write('action.settings', $action_settings);
+
     // Verify that both appear as ready to import.
     $this->drupalGet('admin/config/development/configuration');
     $this->assertText($name);
     $this->assertText($dynamic_name);
+    $this->assertText('system.module');
+    $this->assertText('system.theme');
+    $this->assertText('action.settings');
+    $this->assertText('bartik.settings');
     $this->assertFieldById('edit-submit', t('Import all'));
 
     // Import and verify that both do not appear anymore.
     $this->drupalPostForm(NULL, array(), t('Import all'));
     $this->assertNoText($name);
     $this->assertNoText($dynamic_name);
+    $this->assertNoText('system.module');
+    $this->assertNoText('system.theme');
+    $this->assertNoText('action.settings');
+    $this->assertNoText('bartik.settings');
+
     $this->assertNoFieldById('edit-submit', t('Import all'));
 
     // Verify that there are no further changes to import.
@@ -88,6 +124,73 @@ function testImport() {
 
     // Verify the cache got cleared.
     $this->assertTrue(isset($GLOBALS['hook_cache_flush']));
+
+    $this->rebuildContainer();
+    $this->assertTrue(\Drupal::moduleHandler()->moduleExists('ban'), 'Ban module enabled during import.');
+    $this->assertTrue(\Drupal::database()->schema()->tableExists('ban_ip'), 'The database table ban_ip exists.');
+    $this->assertTrue(\Drupal::moduleHandler()->moduleExists('action'), 'Action module enabled during import.');
+
+    $theme_info = \Drupal::service('theme_handler')->listInfo();
+    $this->assertTrue(isset($theme_info['bartik']) && $theme_info['bartik']->status, 'Bartik theme enabled during import.');
+
+    // The configuration object system.theme will be saved twice during config
+    // import. Once during enabling the system and once during importing the
+    // new default setting.
+    $this->assertEqual(\Drupal::state()->get('ConfigImportUITest.system.theme.save', 0), 2, 'The system.theme configuration saved twice during import.');
+
+    // Verify that the action.settings configuration object was only written
+    // once during the import process and only with the value set in the staged
+    // configuration. This verifies that the module's default configuration is
+    // used during configuration import and, additionally, that after installing
+    // a module, that configuration is not synced twice.
+    $recursion_limit_values = \Drupal::state()->get('ConfigImportUITest.action.settings.recursion_limit', array());
+    $this->assertIdentical($recursion_limit_values, array(50));
+
+    $system_module = \Drupal::config('system.module')->get();
+    unset($system_module['enabled']['action']);
+    unset($system_module['enabled']['ban']);
+    $staging->write('system.module', $system_module);
+    $staging->delete('action.settings');
+
+    $system_theme = \Drupal::config('system.theme')->get();
+    unset($system_theme['enabled']['bartik']);
+    $system_theme['default'] = 'stark';
+    $system_theme['admin'] = 'stark';
+    $staging->write('system.theme', $system_theme);
+    $staging->write('system.theme.disabled', array('bartik' => 0));
+
+    // Reset counter.
+    \Drupal::state()->set('ConfigImportUITest.system.theme.save', 0);
+
+    // Verify that both appear as ready to import.
+    $this->drupalGet('admin/config/development/configuration');
+    $this->assertText('system.module');
+    $this->assertText('system.theme');
+    $this->assertText('system.theme.disabled');
+    $this->assertText('action.settings');
+
+    // Import and verify that both do not appear anymore.
+    $this->drupalPostForm(NULL, array(), t('Import all'));
+    $this->assertNoText('system.module');
+    $this->assertNoText('system.theme');
+    $this->assertNoText('system.theme.disabled');
+    $this->assertNoText('action.settings');
+
+    $this->rebuildContainer();
+    $this->assertFalse(\Drupal::moduleHandler()->moduleExists('ban'), 'Ban module uninstalled during import.');
+    $this->assertFalse(\Drupal::database()->schema()->tableExists('ban_ip'), 'The database table ban_ip does not exist.');
+    $this->assertFalse(\Drupal::moduleHandler()->moduleExists('action'), 'Action module uninstalled during import.');
+    // This is because it will be updated to change the default theme, remove
+    // Bartik and then set the admin theme.
+    $this->assertEqual(\Drupal::state()->get('ConfigImportUITest.system.theme.save', 0), 3, 'The system.theme configuration saved thrice during import.');
+
+    $theme_info = \Drupal::service('theme_handler')->listInfo();
+    $this->assertTrue(isset($theme_info['bartik']) && !$theme_info['bartik']->status, 'Bartik theme disabled during import.');
+
+    // Verify that the action.settings configuration object was only deleted
+    // once during the import process.
+    $delete_called = \Drupal::state()->get('ConfigImportUITest.action.settings.delete', 0);
+    $this->assertIdentical($delete_called, 1, "The action.settings configuration was deleted once during configuration import.");
   }
 
   /**
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigImporterTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigImporterTest.php
index b01ddab..a132946 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigImporterTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigImporterTest.php
@@ -60,7 +60,9 @@ function setUp() {
       $this->container->get('event_dispatcher'),
       $this->container->get('config.manager'),
       $this->container->get('lock'),
-      $this->container->get('config.typed')
+      $this->container->get('config.typed'),
+      $this->container->get('module_handler'),
+      $this->container->get('theme_handler')
     );
     $this->copyConfig($this->container->get('config.storage'), $this->container->get('config.storage.staging'));
   }
diff --git a/core/modules/config/tests/config_import_test/config_import_test.info.yml b/core/modules/config/tests/config_import_test/config_import_test.info.yml
new file mode 100644
index 0000000..87cdd02
--- /dev/null
+++ b/core/modules/config/tests/config_import_test/config_import_test.info.yml
@@ -0,0 +1,6 @@
+name: 'Configuration import test'
+type: module
+package: Testing
+version: VERSION
+core: 8.x
+hidden: true
diff --git a/core/modules/config/tests/config_import_test/config_import_test.module b/core/modules/config/tests/config_import_test/config_import_test.module
new file mode 100644
index 0000000..936b72b
--- /dev/null
+++ b/core/modules/config/tests/config_import_test/config_import_test.module
@@ -0,0 +1,6 @@
+<?php
+
+/**
+ * @file
+ * Provides configuration import test helpers.
+ */
diff --git a/core/modules/config/tests/config_import_test/config_import_test.services.yml b/core/modules/config/tests/config_import_test/config_import_test.services.yml
new file mode 100644
index 0000000..997fd11
--- /dev/null
+++ b/core/modules/config/tests/config_import_test/config_import_test.services.yml
@@ -0,0 +1,6 @@
+services:
+  config_import_test.event_subscriber:
+    class: Drupal\config_import_test\EventSubscriber
+    tags:
+      - { name: event_subscriber }
+    arguments: ['@state']
\ No newline at end of file
diff --git a/core/modules/config/tests/config_import_test/lib/Drupal/config_import_test/EventSubscriber.php b/core/modules/config/tests/config_import_test/lib/Drupal/config_import_test/EventSubscriber.php
new file mode 100644
index 0000000..819e560
--- /dev/null
+++ b/core/modules/config/tests/config_import_test/lib/Drupal/config_import_test/EventSubscriber.php
@@ -0,0 +1,87 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\config_import_test\EventSubscriber.
+ */
+
+namespace Drupal\config_import_test;
+
+use Drupal\Core\Config\ConfigCrudEvent;
+use Drupal\Core\Config\ConfigEvent;
+use Drupal\Core\Config\ConfigEvents;
+use Drupal\Core\Config\ConfigImporterEvent;
+use Drupal\Core\KeyValueStore\StateInterface;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+
+/**
+ * Config import subscriber for config import events.
+ */
+class EventSubscriber implements EventSubscriberInterface {
+
+  /**
+   * The key value store.
+   *
+   * @var \Drupal\Core\KeyValueStore\StateInterface
+   */
+  protected $state;
+
+  /**
+   * Constructs the event subscriber.
+   *
+   * @param \Drupal\Core\KeyValueStore\StateInterface $state
+   *   The key value store.
+   */
+  public function __construct(StateInterface $state) {
+    $this->state = $state;
+  }
+
+  /**
+   * Validates the configuration to be imported.
+   *
+   * @param \Drupal\Core\Config\ConfigImporterEvent $event
+   *   The Event to process.
+   *
+   * @throws \Drupal\Core\Config\ConfigNameException
+   */
+  public function onConfigImporterValidate(ConfigImporterEvent $event) {
+
+  }
+
+  public function onConfigSave(ConfigCrudEvent $event) {
+    $config = $event->getConfig();
+    if ($config->getName() == 'action.settings') {
+      $values = $this->state->get('ConfigImportUITest.action.settings.recursion_limit', array());
+      $values[] = $config->get('recursion_limit');
+      $this->state->set('ConfigImportUITest.action.settings.recursion_limit', $values);
+    }
+    if ($config->getName() == 'system.theme') {
+      $value = $this->state->get('ConfigImportUITest.system.theme.save', 0);
+      $this->state->set('ConfigImportUITest.system.theme.save', $value + 1);
+    }
+  }
+
+  public function onConfigDelete(ConfigCrudEvent $event) {
+    $config = $event->getConfig();
+    if ($config->getName() == 'action.settings') {
+      $value = $this->state->get('ConfigImportUITest.action.settings.delete', 0);
+      $this->state->set('ConfigImportUITest.action.settings.delete', $value + 1);
+    }
+  }
+
+  /**
+   * Registers the methods in this class that should be listeners.
+   *
+   * @return array
+   *   An array of event listener definitions.
+   */
+  static function getSubscribedEvents() {
+    //$events['config.importer.validate'][] = array('onConfigImporterValidate', 40);
+    //$events['config.installer.validate'][] = array('onConfigImporterValidate', 40);
+    $events[ConfigEvents::SAVE][] = array('onConfigSave', 40);
+    $events[ConfigEvents::DELETE][] = array('onConfigDelete', 40);
+    return $events;
+  }
+
+}
\ No newline at end of file
diff --git a/core/modules/contact/contact.install b/core/modules/contact/contact.install
index a67134e..477f359 100644
--- a/core/modules/contact/contact.install
+++ b/core/modules/contact/contact.install
@@ -15,5 +15,11 @@ function contact_install() {
   if (empty($site_mail)) {
     $site_mail = ini_get('sendmail_from');
   }
-  \Drupal::config('contact.category.feedback')->set('recipients', array($site_mail))->save();
+  $config = \Drupal::config('contact.category.feedback');
+  // Update the recipients if the default configuration entity has been created.
+  // We should never rely on default config entities as during enabling a module
+  // during config sync they will not exist.
+  if (!$config->isNew()) {
+    \Drupal::config('contact.category.feedback')->set('recipients', array($site_mail))->save();
+  }
 }
diff --git a/core/modules/content_translation/content_translation.install b/core/modules/content_translation/content_translation.install
index e474d69..9c365d7 100644
--- a/core/modules/content_translation/content_translation.install
+++ b/core/modules/content_translation/content_translation.install
@@ -87,6 +87,19 @@ function content_translation_install() {
   // hook_module_implements_alter() is run among the last ones.
   module_set_weight('content_translation', 10);
   \Drupal::service('language_negotiator')->saveConfiguration(Language::TYPE_CONTENT, array(LanguageNegotiationUrl::METHOD_ID => 0));
+
+  $config_names = \Drupal::configFactory()->listAll('field.field.');
+  foreach ($config_names as $name) {
+    \Drupal::config($name)
+      ->set('settings.translation_sync', FALSE)
+      ->save();
+  }
+  $config_names = \Drupal::configFactory()->listAll('field.instance.');
+  foreach ($config_names as $name) {
+    \Drupal::config($name)
+      ->set('settings.translation_sync', FALSE)
+      ->save();
+  }
 }
 
 /**
@@ -104,3 +117,21 @@ function content_translation_enable() {
   $message = t('<a href="!settings_url">Enable translation</a> for <em>content types</em>, <em>taxonomy vocabularies</em>, <em>accounts</em>, or any other element you wish to translate.', $t_args);
   drupal_set_message($message, 'warning');
 }
+
+/**
+ * Implements hook_uninstall().
+ */
+function content_translation_uninstall() {
+  $config_names = \Drupal::configFactory()->listAll('field.field.');
+  foreach ($config_names as $name) {
+    \Drupal::config($name)
+      ->clear('settings.translation_sync')
+      ->save();
+  }
+  $config_names = \Drupal::configFactory()->listAll('field.instance.');
+  foreach ($config_names as $name) {
+    \Drupal::config($name)
+      ->clear('settings.translation_sync')
+      ->save();
+  }
+}
diff --git a/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php b/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
index 1a2bc5e..2da0a8a 100644
--- a/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
+++ b/core/modules/entity/lib/Drupal/entity/EntityDisplayBase.php
@@ -178,7 +178,11 @@ public function calculateDependencies() {
     // Depend on configured modes.
     if ($this->mode != 'default') {
       $mode_entity = \Drupal::entityManager()->getStorageController($this->displayContext . '_mode')->load($target_entity_type->id() . '.' . $this->mode);
-      $this->addDependency('entity', $mode_entity->getConfigDependencyName());
+      // It is possible to add modes via hook_entity_form_mode_info_alter().
+      // @see entity_test_entity_form_mode_info_alter()
+      if ($mode_entity) {
+        $this->addDependency('entity', $mode_entity->getConfigDependencyName());
+      }
     }
     return $this->dependencies;
   }
diff --git a/core/modules/field/lib/Drupal/field/Entity/FieldInstanceConfig.php b/core/modules/field/lib/Drupal/field/Entity/FieldInstanceConfig.php
index 3b2b503..d1731d3 100644
--- a/core/modules/field/lib/Drupal/field/Entity/FieldInstanceConfig.php
+++ b/core/modules/field/lib/Drupal/field/Entity/FieldInstanceConfig.php
@@ -793,4 +793,11 @@ public function hasCustomStorage() {
     return $this->field->hasCustomStorage();
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isDeleted() {
+    return $this->deleted;
+  }
+
 }
diff --git a/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php b/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
index e796caa..6c84282 100644
--- a/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
+++ b/core/modules/field/lib/Drupal/field/FieldInstanceConfigInterface.php
@@ -40,4 +40,12 @@ public function allowBundleRename();
    */
   public function targetBundle();
 
+  /**
+   * Gets the deleted flag of the field instance.
+   *
+   * @return bool
+   *   Returns TRUE if the instance is deleted.
+   */
+  public function isDeleted();
+
 }
diff --git a/core/modules/forum/config/field.field.forum.forum_container.yml b/core/modules/forum/config/field.field.forum.forum_container.yml
index af5ebf2..1c7d8a4 100644
--- a/core/modules/forum/config/field.field.forum.forum_container.yml
+++ b/core/modules/forum/config/field.field.forum.forum_container.yml
@@ -1,4 +1,4 @@
-id: taxonomy_term.forum_container
+id: forum.forum_container
 status: true
 langcode: en
 name: forum_container
diff --git a/core/modules/forum/forum.install b/core/modules/forum/forum.install
index b5f0e0a..da46646 100644
--- a/core/modules/forum/forum.install
+++ b/core/modules/forum/forum.install
@@ -16,72 +16,74 @@ function forum_install() {
   $locked['forum'] = 'forum';
   \Drupal::state()->set('node.type.locked', $locked);
 
-  // Create the 'taxonomy_forums' field if it doesn't already exist. If forum
-  // is being enabled at the same time as taxonomy after both modules have been
-  // enabled, the field might exist but still be marked inactive.
-  if (!field_info_field('node', 'taxonomy_forums')) {
-    entity_create('field_config', array(
-      'name' => 'taxonomy_forums',
-      'entity_type' => 'node',
-      'type' => 'taxonomy_term_reference',
-      'settings' => array(
-        'allowed_values' => array(
-          array(
-            'vocabulary' => 'forums',
-            'parent' => 0,
+  if (!\Drupal::service('config.installer')->isSyncing()) {
+    // Create the 'taxonomy_forums' field if it doesn't already exist. If forum
+    // is being enabled at the same time as taxonomy after both modules have been
+    // enabled, the field might exist but still be marked inactive.
+    if (!field_info_field('node', 'taxonomy_forums')) {
+      entity_create('field_config', array(
+        'name' => 'taxonomy_forums',
+        'entity_type' => 'node',
+        'type' => 'taxonomy_term_reference',
+        'settings' => array(
+          'allowed_values' => array(
+            array(
+              'vocabulary' => 'forums',
+              'parent' => 0,
+            ),
           ),
         ),
-      ),
-    ))->save();
-
-    // Create a default forum so forum posts can be created.
-    $term = entity_create('taxonomy_term', array(
-      'name' => t('General discussion'),
-      'description' => '',
-      'parent' => array(0),
-      'vid' => 'forums',
-      'forum_container' => 0,
+      ))->save();
+  
+      // Create a default forum so forum posts can be created.
+      $term = entity_create('taxonomy_term', array(
+        'name' => t('General discussion'),
+        'description' => '',
+        'parent' => array(0),
+        'vid' => 'forums',
+        'forum_container' => 0,
+      ));
+      $term->save();
+  
+      // Create the instance on the bundle.
+      entity_create('field_instance_config', array(
+        'field_name' => 'taxonomy_forums',
+        'entity_type' => 'node',
+        'label' => 'Forums',
+        'bundle' => 'forum',
+        'required' => TRUE,
+      ))->save();
+  
+        // Assign form display settings for the 'default' form mode.
+        entity_get_form_display('node', 'forum', 'default')
+          ->setComponent('taxonomy_forums', array(
+            'type' => 'options_select',
+          ))
+          ->save();
+  
+      // Assign display settings for the 'default' and 'teaser' view modes.
+      entity_get_display('node', 'forum', 'default')
+        ->setComponent('taxonomy_forums', array(
+          'type' => 'taxonomy_term_reference_link',
+          'weight' => 10,
+        ))
+        ->save();
+      entity_get_display('node', 'forum', 'teaser')
+        ->setComponent('taxonomy_forums', array(
+          'type' => 'taxonomy_term_reference_link',
+          'weight' => 10,
+        ))
+        ->save();
+    }
+    // Add the comment field to the forum node type.
+    $fields = entity_load_multiple_by_properties('field_config', array(
+      'type' => 'comment',
+      'name' => 'comment_forum',
+      'include_deleted' => FALSE,
     ));
-    $term->save();
-
-    // Create the instance on the bundle.
-    entity_create('field_instance_config', array(
-      'field_name' => 'taxonomy_forums',
-      'entity_type' => 'node',
-      'label' => 'Forums',
-      'bundle' => 'forum',
-      'required' => TRUE,
-    ))->save();
-
-    // Assign form display settings for the 'default' form mode.
-    entity_get_form_display('node', 'forum', 'default')
-      ->setComponent('taxonomy_forums', array(
-        'type' => 'options_select',
-      ))
-      ->save();
-
-    // Assign display settings for the 'default' and 'teaser' view modes.
-    entity_get_display('node', 'forum', 'default')
-      ->setComponent('taxonomy_forums', array(
-        'type' => 'taxonomy_term_reference_link',
-        'weight' => 10,
-      ))
-      ->save();
-    entity_get_display('node', 'forum', 'teaser')
-      ->setComponent('taxonomy_forums', array(
-        'type' => 'taxonomy_term_reference_link',
-        'weight' => 10,
-      ))
-      ->save();
-  }
-  // Add the comment field to the forum node type.
-  $fields = entity_load_multiple_by_properties('field_config', array(
-    'type' => 'comment',
-    'name' => 'comment_forum',
-    'include_deleted' => FALSE,
-  ));
-  if (empty($fields)) {
-    Drupal::service('comment.manager')->addDefaultField('node', 'forum', 'comment_forum');
+    if (empty($fields)) {
+      Drupal::service('comment.manager')->addDefaultField('node', 'forum', 'comment_forum');
+    }
   }
 }
 
diff --git a/core/modules/node/config/views.view.archive.yml b/core/modules/node/config/views.view.archive.yml
index 1151b1a..943c220 100644
--- a/core/modules/node/config/views.view.archive.yml
+++ b/core/modules/node/config/views.view.archive.yml
@@ -8,7 +8,7 @@ display:
     id: default
     display_title: Master
     display_plugin: default
-    position: 1
+    position: 0
     display_options:
       query:
         type: views_query
@@ -140,7 +140,7 @@ display:
     id: block_1
     display_title: Block
     display_plugin: block
-    position: 3
+    position: 1
     display_options:
       query:
         type: views_query
diff --git a/core/modules/node/config/views.view.content_recent.yml b/core/modules/node/config/views.view.content_recent.yml
index 09993b7..2dec730 100644
--- a/core/modules/node/config/views.view.content_recent.yml
+++ b/core/modules/node/config/views.view.content_recent.yml
@@ -8,7 +8,7 @@ display:
     display_plugin: default
     id: default
     display_title: Master
-    position: 1
+    position: 0
     display_options:
       access:
         type: perm
diff --git a/core/modules/node/config/views.view.glossary.yml b/core/modules/node/config/views.view.glossary.yml
index 0edc991..03a7a18 100644
--- a/core/modules/node/config/views.view.glossary.yml
+++ b/core/modules/node/config/views.view.glossary.yml
@@ -8,7 +8,7 @@ display:
     id: default
     display_title: Master
     display_plugin: default
-    position: 1
+    position: 0
     display_options:
       query:
         type: views_query
@@ -306,7 +306,7 @@ display:
     id: page_1
     display_title: Page
     display_plugin: page
-    position: 2
+    position: 1
     display_options:
       query:
         type: views_query
@@ -320,7 +320,7 @@ display:
     id: attachment_1
     display_title: Attachment
     display_plugin: attachment
-    position: 3
+    position: 2
     display_options:
       query:
         type: views_query
diff --git a/core/modules/node/node.install b/core/modules/node/node.install
index a6af612..36f8345 100644
--- a/core/modules/node/node.install
+++ b/core/modules/node/node.install
@@ -459,7 +459,9 @@ function node_uninstall() {
   $types = \Drupal::configFactory()->listAll('node.type.');
   foreach ($types as $config_name) {
     $type = \Drupal::config($config_name)->get('type');
-    \Drupal::config('language.settings')->clear('node. ' . $type . '.language.default_configuration')->save();
+    if (\Drupal::moduleHandler()->moduleExists('language')) {
+      \Drupal::config('language.settings')->clear('node. ' . $type . '.language.default_configuration')->save();
+    }
   }
 
   // Delete remaining general module variables.
diff --git a/core/modules/search/lib/Drupal/search/SearchPageRepository.php b/core/modules/search/lib/Drupal/search/SearchPageRepository.php
index db1e57f..37d0dd0 100644
--- a/core/modules/search/lib/Drupal/search/SearchPageRepository.php
+++ b/core/modules/search/lib/Drupal/search/SearchPageRepository.php
@@ -87,7 +87,7 @@ public function getDefaultSearchPage() {
     }
 
     // Otherwise, use the first active search page.
-    return reset($search_pages);
+    return is_array($search_pages) ? reset($search_pages) : FALSE;
   }
 
   /**
diff --git a/core/modules/search/search.module b/core/modules/search/search.module
index 62822e5..919b349 100644
--- a/core/modules/search/search.module
+++ b/core/modules/search/search.module
@@ -142,11 +142,14 @@ function search_preprocess_block(&$variables) {
  * Implements hook_menu_link_defaults().
  */
 function search_menu_link_defaults() {
-  $links['search.view'] = array(
-    'link_title' => 'Search',
-    'route_name' => 'search.view',
-    'type' => MENU_SUGGESTED_ITEM,
-  );
+  // Create a default search page
+  if (\Drupal::service('search.search_page_repository')->getDefaultSearchPage()) {
+    $links['search.view'] = array(
+      'link_title' => 'Search',
+      'route_name' => 'search.view',
+      'type' => MENU_SUGGESTED_ITEM,
+    );
+  }
   $links['search.settings'] = array(
     'link_title' => 'Search settings',
     'parent' => 'system.admin_config_search',
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 065d4c8..40c5f90 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -1510,7 +1510,9 @@ public function configImporter() {
         $this->container->get('event_dispatcher'),
         $this->container->get('config.manager'),
         $this->container->get('lock'),
-        $this->container->get('config.typed')
+        $this->container->get('config.typed'),
+        $this->container->get('module_handler'),
+        $this->container->get('theme_handler')
       );
     }
     // Always recalculate the changelist when called.
diff --git a/core/modules/simpletest/simpletest.install b/core/modules/simpletest/simpletest.install
index 917a938..82e1ebb 100644
--- a/core/modules/simpletest/simpletest.install
+++ b/core/modules/simpletest/simpletest.install
@@ -182,7 +182,7 @@ function simpletest_uninstall() {
   // Do not clean the environment in case the Simpletest module is uninstalled
   // in a (recursive) test for itself, since simpletest_clean_environment()
   // would also delete the test site of the parent test process.
-  if (!DRUPAL_TEST_IN_CHILD_SITE) {
+  if (!drupal_valid_test_ua()) {
     simpletest_clean_environment();
   }
   // Delete verbose test output and any other testing framework files.
diff --git a/core/modules/system/config/schema/system.schema.yml b/core/modules/system/config/schema/system.schema.yml
index 157805c..6140e39 100644
--- a/core/modules/system/config/schema/system.schema.yml
+++ b/core/modules/system/config/schema/system.schema.yml
@@ -466,9 +466,11 @@ system.theme.global:
           type: boolean
           label: 'Use default'
 
+# The weight for disabled themes is ignored but the same format for
+# system.theme:enabled is used for consistency.
 system.theme.disabled:
   type: sequence
   label: 'Disabled themes'
   sequence:
-    - type: string
-      label: 'Theme'
+    - type: integer
+      label: 'Weight'
diff --git a/core/modules/system/config/system.theme.disabled.yml b/core/modules/system/config/system.theme.disabled.yml
new file mode 100644
index 0000000..bc8d1d5
--- /dev/null
+++ b/core/modules/system/config/system.theme.disabled.yml
@@ -0,0 +1,3 @@
+# An empty array representing no disabled themes. This file needs to exist since
+# all simple configuration must exist.
+{  }
\ No newline at end of file
diff --git a/core/modules/taxonomy/config/views.view.taxonomy_term.yml b/core/modules/taxonomy/config/views.view.taxonomy_term.yml
index 10ce059..6477894 100644
--- a/core/modules/taxonomy/config/views.view.taxonomy_term.yml
+++ b/core/modules/taxonomy/config/views.view.taxonomy_term.yml
@@ -8,7 +8,7 @@ display:
     id: default
     display_title: Master
     display_plugin: default
-    position: 1
+    position: 0
     display_options:
       query:
         type: views_query
@@ -184,7 +184,7 @@ display:
     id: page_1
     display_title: Page
     display_plugin: page
-    position: 2
+    position: 1
     display_options:
       query:
         type: views_query
@@ -195,7 +195,7 @@ display:
     id: feed_1
     display_title: Feed
     display_plugin: feed
-    position: 3
+    position: 2
     display_options:
       query:
         type: views_query
diff --git a/core/modules/user/config/views.view.who_s_new.yml b/core/modules/user/config/views.view.who_s_new.yml
index f5bee58..45566ae 100644
--- a/core/modules/user/config/views.view.who_s_new.yml
+++ b/core/modules/user/config/views.view.who_s_new.yml
@@ -4,20 +4,11 @@ core: 8.x
 description: 'Shows a list of the newest user accounts on the site.'
 status: true
 display:
-  block_1:
-    display_plugin: block
-    id: block_1
-    display_title: 'Who''s new'
-    position: 1
-    display_options:
-      display_description: 'A list of new users'
-      block_description: 'Who''s new'
-      block_category: User
   default:
     display_plugin: default
     id: default
     display_title: Master
-    position: 1
+    position: 0
     display_options:
       access:
         type: perm
@@ -166,6 +157,15 @@ display:
       empty: {  }
       relationships: {  }
       arguments: {  }
+  block_1:
+    display_plugin: block
+    id: block_1
+    display_title: 'Who''s new'
+    position: 1
+    display_options:
+      display_description: 'A list of new users'
+      block_description: 'Who''s new'
+      block_category: User
 label: 'Who''s new'
 module: user
 id: who_s_new
diff --git a/core/modules/user/config/views.view.who_s_online.yml b/core/modules/user/config/views.view.who_s_online.yml
index efe344f..323825b 100644
--- a/core/modules/user/config/views.view.who_s_online.yml
+++ b/core/modules/user/config/views.view.who_s_online.yml
@@ -8,7 +8,7 @@ display:
     display_plugin: default
     id: default
     display_title: Master
-    position: 1
+    position: 0
     display_options:
       access:
         type: perm
diff --git a/core/profiles/standard/config/entity.view_display.node.article.default.yml b/core/profiles/standard/config/entity.view_display.node.article.default.yml
index c4f2c85..81f0545 100644
--- a/core/profiles/standard/config/entity.view_display.node.article.default.yml
+++ b/core/profiles/standard/config/entity.view_display.node.article.default.yml
@@ -4,6 +4,13 @@ bundle: article
 mode: default
 status: true
 content:
+  field_image:
+    label: hidden
+    type: image
+    settings:
+      image_style: large
+      image_link: ''
+    weight: -1
   body:
     label: hidden
     type: text_default
@@ -14,13 +21,6 @@ content:
     weight: 10
     label: above
     settings: {  }
-  field_image:
-    label: hidden
-    type: image
-    settings:
-      image_style: large
-      image_link: ''
-    weight: -1
 dependencies:
   entity:
     - field.instance.node.article.body
diff --git a/core/profiles/standard/config/entity.view_display.node.article.teaser.yml b/core/profiles/standard/config/entity.view_display.node.article.teaser.yml
index a88fc06..e21e3cf 100644
--- a/core/profiles/standard/config/entity.view_display.node.article.teaser.yml
+++ b/core/profiles/standard/config/entity.view_display.node.article.teaser.yml
@@ -4,6 +4,13 @@ bundle: article
 mode: teaser
 status: true
 content:
+  field_image:
+    label: hidden
+    type: image
+    settings:
+      image_style: medium
+      image_link: content
+    weight: -1
   body:
     label: hidden
     type: text_summary_or_trimmed
@@ -15,13 +22,6 @@ content:
     weight: 10
     label: above
     settings: {  }
-  field_image:
-    label: hidden
-    type: image
-    settings:
-      image_style: medium
-      image_link: content
-    weight: -1
 dependencies:
   entity:
     - entity.view_mode.node.teaser