diff --git a/core/includes/update.inc b/core/includes/update.inc
index 67af504..9c9a65c 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -215,19 +215,20 @@ function update_do_one($module, $number, $dependency_map, &$context) {
     drupal_set_installed_schema_version($module, $number);
   }
 
-  $context['message'] = 'Updating ' . Html::escape($module) . ' module';
+  $context['message'] = t('Updating @module', ['@module' => $module]);
 }
 
 /**
- * Executes a single hook_post_update_$name().
+ * Executes a single hook_post_update_NAME().
  *
  * @param string $function
  *   The function name, that should be executed.
  * @param array $context
  *   The batch context array.
  */
-function update_post_update_do_one($function, &$context) {
+function update_invoke_post_update($function, &$context) {
   $ret = [];
+
   list($module, ) = explode('_post_update_', $function);
   module_load_include('php', $module, $module . '.post_update');
   if (function_exists($function)) {
@@ -235,10 +236,10 @@ function update_post_update_do_one($function, &$context) {
       $ret['results']['query'] = $function($context['sandbox']);
       $ret['results']['success'] = TRUE;
 
-      $key_value_store = \Drupal::keyValue('update_test_post_update');
-      $executed_updates = $key_value_store->get('core.update__post_update', []);
+      $key_value_store = \Drupal::keyValue('update__post_update');
+      $executed_updates = $key_value_store->get('existing_updates', []);
       $executed_updates[] = $function;
-      $key_value_store->set('core.update__post_update', $executed_updates);
+      $key_value_store->set($module, $executed_updates);
     }
       // @TODO We may want to do different error handling for different
       // exception types, but for now we'll just log the exception and
@@ -267,7 +268,7 @@ function update_post_update_do_one($function, &$context) {
     $context['results']['#abort'][] = $function;
   }
 
-  $context['message'] = 'Updating content after: ' . Html::escape($function);
+  $context['message'] = t('Post updating @module', ['@module' => $module]);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
index ab11469..c088eed 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
@@ -91,6 +91,13 @@ class ExtensionDiscovery {
   protected $fileCache;
 
   /**
+   * The site path.
+   *
+   * @var string
+   */
+  protected $sitePath;
+
+  /**
    * Constructs a new ExtensionDiscovery object.
    *
    * @param string $root
@@ -180,7 +187,7 @@ public function scan($type, $include_tests = NULL) {
       $searchdirs[static::ORIGIN_SITE] = \Drupal::service('site.path');
     }
     else {
-      $searchdirs[static::ORIGIN_SITE] = isset($this->sitePath) ? $this->sitePath : DrupalKernel::findSitePath(Request::createFromGlobals());
+      $searchdirs[static::ORIGIN_SITE] = $this->sitePath ?: DrupalKernel::findSitePath(Request::createFromGlobals());
     }
 
     // Unless an explicit value has been passed, manually check whether we are
diff --git a/core/lib/Drupal/Core/Extension/module.api.php b/core/lib/Drupal/Core/Extension/module.api.php
index 264dc4c..b4b0cf8 100644
--- a/core/lib/Drupal/Core/Extension/module.api.php
+++ b/core/lib/Drupal/Core/Extension/module.api.php
@@ -666,7 +666,7 @@ function hook_update_N(&$sandbox) {
  * stage Drupal is already fully repaired so you can use any API as you wish.
  *
  * Note: In contrast to hook_update_N there is no enforced order, so you can
- * also use machine names.
+ * also use machine names for the name of those updates.
  *
  * @param array $sandbox
  *   Stores information for batch updates. See above for more information.
@@ -675,7 +675,7 @@ function hook_update_N(&$sandbox) {
  *   In case of error, update hooks should throw an instance of
  *   Drupal\Core\Utility\UpdateException with a meaningful message for the user.
  *   If a database query fails for whatever reason, it will throw a
- *   PDOException.ame for the name of those updates.
+ *   PDOException.
  *
  * @return string|null
  *   Optionally, update hooks may return a translated string that will be
@@ -684,9 +684,9 @@ function hook_update_N(&$sandbox) {
  *
  * @ingroup update_api
  *
- * @see hook_update_N
+ * @see hook_update_N()
  */
-function hook_post_update_X(&$sandbox) {
+function hook_post_update_NAME(&$sandbox) {
   $node = \Drupal\node\Entity\Node::load(123);
   $node->setTitle('foo');
   $node->save();
diff --git a/core/lib/Drupal/Core/Update/UpdateRegistry.php b/core/lib/Drupal/Core/Update/UpdateRegistry.php
index b7d3b67..949d076 100644
--- a/core/lib/Drupal/Core/Update/UpdateRegistry.php
+++ b/core/lib/Drupal/Core/Update/UpdateRegistry.php
@@ -12,10 +12,10 @@
 use Drupal\Core\KeyValueStore\KeyValueStoreInterface;
 
 /**
- * Provides all and missing hook_$updateName_X implementations.
+ * Provides all and missing hook_$updateName_NAME implementations.
  *
  * It therefore scans for functions in $module.$updateName.inc named like
- * $module_$updateName_X with X being a machine name.
+ * $module_$updateName_NAME with NAME being a machine name.
  */
 class UpdateRegistry {
 
@@ -68,7 +68,7 @@ public function __construct($root, $site_path, array $enabled_modules, KeyValueS
    * @return callable[]
    */
   protected function getAvailableUpdateFunctions() {
-    $regexp = '/^(?<module>.+)_' . $this->updateName . '_(?<version>.+)$/';
+    $regexp = '/^(?<module>.+)_' . $this->updateName . '_(?<name>.+)$/';
     $functions = get_defined_functions();
 
     $updates = [];
@@ -76,7 +76,7 @@ protected function getAvailableUpdateFunctions() {
       // If this function is a module update function, add it to the list of
       // module updates.
       if (preg_match($regexp, $function, $matches)) {
-        $updates[] = $matches['module'] . '_' . $this->updateName . '_' . $matches['version'];
+        $updates[] = $matches['module'] . '_' . $this->updateName . '_' . $matches['name'];
       }
     }
 
@@ -84,7 +84,7 @@ protected function getAvailableUpdateFunctions() {
   }
 
   /**
-   * Find all update functions that haven't been executed
+   * Find all update functions that haven't been executed.
    *
    * @return callable[]
    */
@@ -102,8 +102,8 @@ public function getMissingUpdateFunctions() {
 
     $this->loadUpdateFiles($extensions);
 
-    // First figure out which hook_update got executed already.
-    $existing_update_functions = $this->keyValue->get('core.update__' . $this->updateName, []);
+    // First figure out which hook_{$this->updateName}_NAME got executed already.
+    $existing_update_functions = $this->keyValue->get('existing_updates', []);
 
     $available_update_functions = $this->getAvailableUpdateFunctions();
     $not_executed_update_functions = array_diff($available_update_functions, $existing_update_functions);
@@ -111,8 +111,14 @@ public function getMissingUpdateFunctions() {
     return $not_executed_update_functions;
   }
 
+  /**
+   * Loads all update files for a given list of extension.
+   *
+   * @param \Drupal\Core\Extension\Extension[] $module_extensions
+   *   The extensions used for loading.
+   */
   protected function loadUpdateFiles(array $module_extensions) {
-    // Load all the {$this->updateName}.inc files.
+    // Load all the {$this->updateName}.php files.
     foreach ($this->enabledModules as $module) {
       if (isset($module_extensions[$module])) {
         $this->loadUpdateFile($module_extensions[$module]);
@@ -121,9 +127,10 @@ protected function loadUpdateFiles(array $module_extensions) {
   }
 
   /**
-   * Loads the {$this->updateName}.inc file for a given extension.
+   * Loads the {$this->updateName}.php file for a given extension.
    *
    * @param \Drupal\Core\Extension\Extension $module
+   *   The extension of the module to load its file.
    */
   protected function loadUpdateFile(Extension $module) {
     $filename = $this->root . '/' . $module->getPath() . '/' . $module->getName() . ".{$this->updateName}.php";
@@ -133,21 +140,20 @@ protected function loadUpdateFile(Extension $module) {
   }
 
   /**
-   * Returns a list of all the pending database updates.
+   * Returns a list of all the pending updates.
    *
    * @return array[]
    *   An associative array keyed by module name which contains all information
    *   about database updates that need to be run, and any updates that are not
-   *   going to proceed due to missing requirements. The system module will
-   *   always be listed first.
+   *   going to proceed due to missing requirements.
    *
    *   The subarray for each module can contain the following keys:
    *   - start: The starting update that is to be processed. If this does not
    *       exist then do not process any updates for this module as there are
    *       other requirements that need to be resolved.
    *   - pending: An array of all the pending updates for the module including
-   *       the update number and the description from source code comment for
-   *       each update function. This array is keyed by the update number.
+   *       the description from source code comment for each update function.
+   *       This array is keyed by the update name.
    */
   public function getMissingUpdateList() {
     $functions = $this->getMissingUpdateFunctions();
diff --git a/core/modules/system/src/Controller/DbUpdateController.php b/core/modules/system/src/Controller/DbUpdateController.php
index ab06793..043e61d 100644
--- a/core/modules/system/src/Controller/DbUpdateController.php
+++ b/core/modules/system/src/Controller/DbUpdateController.php
@@ -265,7 +265,7 @@ protected function selection(Request $request) {
           $updates = update_get_update_list();
           break;
         case 'post_update':
-          $after_update_registry = $this->getUpdateAfterRegistry();
+          $after_update_registry = $this->getPostUpdateRegistry();
           $updates = $after_update_registry->getMissingUpdateList();
           break;
       }
@@ -589,7 +589,7 @@ protected function triggerBatch(Request $request) {
       }
     }
 
-    $after_update_registry = $this->getUpdateAfterRegistry();
+    $after_update_registry = $this->getPostUpdateRegistry();
     $post_updates = $after_update_registry->getMissingUpdateFunctions();
 
     if ($post_updates) {
@@ -597,7 +597,7 @@ protected function triggerBatch(Request $request) {
       // functions.
       $operations[] = ['drupal_flush_all_caches', []];
       foreach ($post_updates as $function) {
-        $operations[] = ['update_post_update_do_one', [$function]];
+        $operations[] = ['update_invoke_post_update', [$function]];
       }
     }
 
diff --git a/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
index e82b0c5..8be271f 100644
--- a/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
+++ b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
@@ -20,19 +20,23 @@ class UpdatePostUpdateTest extends UpdatePathTestBase {
   protected function setDatabaseDumpFiles() {
     $this->databaseDumpFiles = [
       __DIR__ . '/../../../tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../tests/fixtures/update/drupal-8.update-post-update-after-enabled.php',
+      __DIR__ . '/../../../tests/fixtures/update/drupal-8.update-test-post-update-enabled.php',
     ];
   }
 
   public function testUpdateAfter() {
     $this->runUpdates();
 
-    $this->assertIdentical([
+    $updates = [
       'update_test_post_update_post_update_first',
       'update_test_post_update_post_update_second',
       'update_test_post_update_post_update_test1',
       'update_test_post_update_post_update_test0',
-    ], \Drupal::state()->get('post_update_test_execution', []));
+    ];
+    $this->assertIdentical($updates, \Drupal::state()->get('post_update_test_execution', []));
+
+    $key_value = \Drupal::keyValue('update__post_update');
+    $this->assertEqual($updates, $key_value->get('existing_updates'));
   }
 
 }
diff --git a/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.yml b/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.info.yml
similarity index 100%
rename from core/modules/system/tests/modules/update_test_post_update/update_test_post_update.yml
rename to core/modules/system/tests/modules/update_test_post_update/update_test_post_update.info.yml
diff --git a/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php b/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
index fe79330..e90acaa 100644
--- a/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
@@ -26,7 +26,7 @@ class UpdateRegistryTest extends UnitTestCase {
    * {@inheritdoc}
    */
   protected function setUp() {
-    parent::setUp(); // TODO: Change the autogenerated stub
+    parent::setUp();
 
     $settings = [];
     $settings['extension_discovery_scan_tests'] = TRUE;
@@ -101,7 +101,7 @@ public function testGetMissingUpdateFunctionsWithNoExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__post_update', [])->wilLReturn([]);
+    $key_value->get('core.update__post_update', [])->willReturn([]);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -123,7 +123,7 @@ public function testGetMissingUpdateFunctionsWithExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__post_update', [])->wilLReturn(['module_a_post_update_a']);
+    $key_value->get('core.update__post_update', [])->willReturn(['module_a_post_update_a']);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -145,7 +145,7 @@ public function testGetMissingUpdateList() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__post_update', [])->wilLReturn([]);
+    $key_value->get('core.update__post_update', [])->willReturn([]);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -170,7 +170,7 @@ public function testGetMissingUpdateListWithExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__post_update', [])->wilLReturn(['module_a_post_update_a']);
+    $key_value->get('core.update__post_update', [])->willReturn(['module_a_post_update_a']);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [