diff --git a/automatic_updates.install b/automatic_updates.install
index 10f6b11..d7ac9f8 100644
--- a/automatic_updates.install
+++ b/automatic_updates.install
@@ -5,15 +5,78 @@
  * Automatic updates install file.
  */
 
+use Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
 use Drupal\Core\StringTranslation\PluralTranslatableMarkup;
+use Drupal\Core\Url;
 
 /**
  * Requirements checks for automatic updates.
  */
 function automatic_updates_requirements() {
   $requirements = [];
+  _automatic_updates_checker_requirements($requirements);
+  _automatic_updates_psa_requirements($requirements);
+  return $requirements;
+}
+
+/**
+ * Display requirements from results of readiness checker.
+ *
+ * @param array $requirements
+ *   The requirements array.
+ */
+function _automatic_updates_checker_requirements(array &$requirements) {
+  /** @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker */
+  $checker = \Drupal::service('automatic_updates.readiness_checker');
+  if (!$checker->isEnabled()) {
+    return;
+  }
+  $checker_results = $checker->results();
+  $last_check_timestamp = $checker->timestamp();
+  $requirements['automatic_updates_readiness'] = [
+    'title' => t('Update readiness checks'),
+    'severity' => REQUIREMENT_OK,
+    'value' => t('Your site is ready to for <a href="@readiness_checks">automatic updates</a>.', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']),
+  ];
+  if (!empty($checker_results)) {
+    $requirements['automatic_updates_readiness']['severity'] = REQUIREMENT_ERROR;
+    $requirements['automatic_updates_readiness']['value'] = new PluralTranslatableMarkup(count($checker_results), '@count check failed:', '@count checks failed:');
+    $requirements['automatic_updates_readiness']['description'] = [
+      '#theme' => 'item_list',
+      '#items' => $checker_results,
+    ];
+  }
+  if (\Drupal::time()->getRequestTime() > $last_check_timestamp + ReadinessCheckerManagerInterface::LAST_CHECKED_WARNING) {
+    $requirements['automatic_updates_readiness']['severity'] = REQUIREMENT_ERROR;
+    $requirements['automatic_updates_readiness']['value'] = t('Your site has not recently checked if it is ready to apply <a href="@readiness_checks">automatic updates</a>.', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']);
+    $readiness_check = Url::fromRoute('automatic_updates.update_readiness');
+    $time_ago = \Drupal::service('date.formatter')->formatTimeDiffSince($last_check_timestamp);
+    if ($last_check_timestamp === 0) {
+      $requirements['automatic_updates_readiness']['description'] = t('<a href="@link">Run readiness checks</a> manually.', [
+        '@link' => $readiness_check->toString(),
+      ]);
+    }
+    elseif ($readiness_check->access()) {
+      $requirements['automatic_updates_readiness']['description'] = t('Last run @time ago. <a href="@link">Run readiness checks</a> manually.', [
+        '@time' => $time_ago,
+        '@link' => $readiness_check->toString(),
+      ]);
+    }
+    else {
+      $requirements['automatic_updates_readiness']['description'] = t('Readiness checks were last run @time ago.', ['@time' => $time_ago]);
+    }
+  }
+}
+
+/**
+ * Display requirements from public service announcements.
+ *
+ * @param array $requirements
+ *   The requirements array.
+ */
+function _automatic_updates_psa_requirements(array &$requirements) {
   if (!\Drupal::config('automatic_updates.settings')->get('enable_psa')) {
-    return $requirements;
+    return;
   }
   /** @var \Drupal\automatic_updates\Services\AutomaticUpdatesPsa $psa */
   $psa = \Drupal::service('automatic_updates.psa');
@@ -31,5 +94,4 @@ function automatic_updates_requirements() {
       '#items' => $messages,
     ];
   }
-  return $requirements;
 }
diff --git a/automatic_updates.module b/automatic_updates.module
index 34ea032..ea7c5ea 100644
--- a/automatic_updates.module
+++ b/automatic_updates.module
@@ -5,6 +5,8 @@
  * Contains automatic_updates.module..
  */
 
+use Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
+
 /**
  * Implements hook_page_top().
  */
@@ -34,5 +36,25 @@ function automatic_updates_page_top(array &$page_top) {
     foreach ($psa->getPublicServiceMessages() as $psa) {
       \Drupal::messenger()->addError($psa);
     }
+    $last_check_timestamp = \Drupal::service('automatic_updates.readiness_checker')->timestamp();
+    if (\Drupal::time()->getRequestTime() > $last_check_timestamp + ReadinessCheckerManagerInterface::LAST_CHECKED_WARNING) {
+      \Drupal::messenger()->addError(t('Your site has not recently run an update readiness check.'));
+    }
+    $results = \Drupal::service('automatic_updates.readiness_checker')->results();
+    if ($results) {
+      \Drupal::messenger()->addError(t('Your site is currently failing readiness checks for automatic updates. It cannot be <a href="@readiness_checks">automatically updated</a> until further action is performed:', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']));
+      foreach ($results as $message) {
+        \Drupal::messenger()->addError($message);
+      }
+    }
   }
 }
+
+/**
+ * Implements hook_cron().
+ */
+function automatic_updates_cron() {
+  /** @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker */
+  $checker = \Drupal::service('automatic_updates.readiness_checker');
+  $checker->run();
+}
diff --git a/automatic_updates.routing.yml b/automatic_updates.routing.yml
index 18c0868..453aa43 100644
--- a/automatic_updates.routing.yml
+++ b/automatic_updates.routing.yml
@@ -7,3 +7,13 @@ automatic_updates.admin_form:
     _permission: 'administer software updates'
   options:
     _admin_route: TRUE
+
+automatic_updates.update_readiness:
+  path: '/admin/config/automatic_updates/readiness'
+  defaults:
+    _controller: '\Drupal\automatic_updates\Controller\ReadinessCheckerController::run'
+    _title: 'Update readiness checking...'
+  requirements:
+    _permission: 'administer software updates'
+  options:
+    _admin_route: TRUE
diff --git a/automatic_updates.services.yml b/automatic_updates.services.yml
index 26d646a..f3c0964 100644
--- a/automatic_updates.services.yml
+++ b/automatic_updates.services.yml
@@ -2,6 +2,10 @@ services:
   logger.channel.automatic_updates:
     parent: logger.channel_base
     arguments: ['automatic_updates']
+  automatic_updates.drupal_finder:
+    class: DrupalFinder\DrupalFinder
+  automatic_updates.filesystem_cache:
+    class: League\Flysystem\Cached\Storage\Memory
   automatic_updates.psa:
     class: Drupal\automatic_updates\Services\AutomaticUpdatesPsa
     arguments:
@@ -13,3 +17,25 @@ services:
       - '@extension.list.profile'
       - '@extension.list.theme'
       - '@logger.channel.automatic_updates'
+  automatic_updates.readiness_checker:
+    class: Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManager
+    arguments:
+      - '@state'
+      - '@config.factory'
+    tags:
+      - { name: service_collector, tag: readiness_checker, call: addChecker }
+  automatic_updates.readonly_checker:
+    class: Drupal\automatic_updates\ReadinessChecker\ReadOnlyFilesystem
+    arguments:
+      - '@logger.channel.automatic_updates'
+      - '@automatic_updates.drupal_finder'
+      - '@automatic_updates.filesystem_cache'
+    tags:
+      - { name: readiness_checker, priority: 100 }
+  automatic_updates.disk_space_checker:
+    class: Drupal\automatic_updates\ReadinessChecker\DiskSpace
+    arguments:
+      - '@logger.channel.automatic_updates'
+      - '@automatic_updates.drupal_finder'
+    tags:
+      - { name: readiness_checker }
diff --git a/composer.json b/composer.json
index 0e18c77..e366d15 100644
--- a/composer.json
+++ b/composer.json
@@ -12,6 +12,9 @@
   },
   "require": {
     "ext-json": "*",
-    "composer/semver": "^1.0@dev"
+    "composer/semver": "^1.0",
+    "league/flysystem": "^1.1",
+    "league/flysystem-cached-adapter": "^1.0",
+    "webflo/drupal-finder": "^1.1"
   }
 }
diff --git a/config/install/automatic_updates.settings.yml b/config/install/automatic_updates.settings.yml
index 085f065..01c1bf1 100644
--- a/config/install/automatic_updates.settings.yml
+++ b/config/install/automatic_updates.settings.yml
@@ -3,3 +3,4 @@
 # https://www.drupal.org/project/automatic_updates/issues/3045273
 psa_endpoint: 'http://localhost/automatic_updates/test-json'
 enable_psa: true
+enable_readiness_checks: true
diff --git a/config/schema/automatic_updates.schema.yml b/config/schema/automatic_updates.schema.yml
index ca29403..eeeb8c8 100644
--- a/config/schema/automatic_updates.schema.yml
+++ b/config/schema/automatic_updates.schema.yml
@@ -8,3 +8,6 @@ automatic_updates.settings:
     enable_psa:
       type: boolean
       label: 'Enable PSA notices'
+    enable_readiness_checks:
+      type: boolean
+      label: 'Enable readiness checks'
diff --git a/src/Controller/ReadinessCheckerController.php b/src/Controller/ReadinessCheckerController.php
new file mode 100644
index 0000000..e91e35a
--- /dev/null
+++ b/src/Controller/ReadinessCheckerController.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Drupal\automatic_updates\Controller;
+
+use Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface;
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\StringTranslation\TranslationInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Class ReadinessCheckerController.
+ */
+class ReadinessCheckerController extends ControllerBase {
+
+  /**
+   * The readiness checker.
+   *
+   * @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface
+   */
+  protected $checker;
+
+  /**
+   * ReadinessCheckerController constructor.
+   *
+   * @param \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker
+   *   The readiness checker.
+   * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
+   *   The string translation service.
+   */
+  public function __construct(ReadinessCheckerManagerInterface $checker, TranslationInterface $string_translation) {
+    $this->checker = $checker;
+    $this->stringTranslation = $string_translation;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('automatic_updates.readiness_checker'),
+      $container->get('string_translation')
+    );
+  }
+
+  /**
+   * Run the readiness checkers.
+   *
+   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   *   A redirect
+   */
+  public function run() {
+    $messages = $this->checker->run();
+    if (empty($messages)) {
+      $this->messenger()->addStatus($this->t('No issues found. Your site is ready to for <a href="@readiness_checks">automatic updates</a>.', ['@readiness_checks' => 'https://www.drupal.org/docs/8/update/automatic-updates#readiness-checks']));
+    }
+    return $this->redirect('automatic_updates.admin_form');
+  }
+
+}
diff --git a/src/Form/AdminForm.php b/src/Form/AdminForm.php
index 78217e8..ed51f7d 100644
--- a/src/Form/AdminForm.php
+++ b/src/Form/AdminForm.php
@@ -4,12 +4,38 @@ namespace Drupal\automatic_updates\Form;
 
 use Drupal\Core\Form\ConfigFormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Administration form for automatic updates.
  */
 class AdminForm extends ConfigFormBase {
 
+  /**
+   * The readiness checker.
+   *
+   * @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface
+   */
+  protected $checker;
+
+  /**
+   * The data formatter.
+   *
+   * @var \Drupal\Core\Datetime\DateFormatterInterface
+   */
+  protected $dateFormatter;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    $instance = parent::create($container);
+    $instance->checker = $container->get('automatic_updates.readiness_checker');
+    $instance->dateFormatter = $container->get('date.formatter');
+    return $instance;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -36,6 +62,18 @@ class AdminForm extends ConfigFormBase {
       '#title' => $this->t('Enable messaging of public service alerts (PSAs)'),
       '#default_value' => $config->get('enable_psa'),
     ];
+    $last_check_timestamp = $this->checker->timestamp();
+    $form['enable_readiness_checks'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Check the readiness of automatically updating the site.'),
+      '#default_value' => $config->get('enable_readiness_checks'),
+    ];
+    if ($this->checker->isEnabled()) {
+      $form['enable_readiness_checks']['#description'] = $this->t('Readiness checks were last run @time ago. Run the readiness checks <a href="@link">manually</a>.', [
+        '@time' => $this->dateFormatter->formatTimeDiffSince($last_check_timestamp),
+        '@link' => Url::fromRoute('automatic_updates.update_readiness')->toString(),
+      ]);
+    }
     return parent::buildForm($form, $form_state);
   }
 
diff --git a/src/ReadinessChecker/DiskSpace.php b/src/ReadinessChecker/DiskSpace.php
new file mode 100644
index 0000000..4809c8b
--- /dev/null
+++ b/src/ReadinessChecker/DiskSpace.php
@@ -0,0 +1,152 @@
+<?php
+
+namespace Drupal\automatic_updates\ReadinessChecker;
+
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use DrupalFinder\DrupalFinder;
+use Psr\Log\LoggerInterface;
+
+/**
+ * Disk space checker.
+ */
+class DiskSpace implements ReadinessCheckerInterface {
+  use StringTranslationTrait;
+
+  /**
+   * Minimum disk space (in bytes) is 100mb.
+   */
+  const MINIMUM_DISK_SPACE = 100000000;
+
+  /**
+   * Megabyte divisor.
+   */
+  const MEGABYTE_DIVISOR = 1000000;
+
+  /**
+   * The logger.
+   *
+   * @var \Psr\Log\LoggerInterface
+   */
+  protected $logger;
+
+  /**
+   * The Drupal root path.
+   *
+   * @var string
+   */
+  protected $drupalRoot;
+
+  /**
+   * The vendor path.
+   *
+   * @var string
+   */
+  protected $vendorPath;
+
+  /**
+   * The drupal finder service.
+   *
+   * @var \DrupalFinder\DrupalFinder
+   */
+  protected $drupalFinder;
+
+  /**
+   * ReadOnlyFilesystem constructor.
+   *
+   * @param \Psr\Log\LoggerInterface $logger
+   *   The logger.
+   * @param \DrupalFinder\DrupalFinder $drupal_finder
+   *   The Drupal finder.
+   */
+  public function __construct(LoggerInterface $logger, DrupalFinder $drupal_finder) {
+    $this->logger = $logger;
+    $this->drupalFinder = $drupal_finder;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function run() {
+    $messages = [];
+    if (!$this->getDrupalRoot()) {
+      $messages[] = $this->t('The Drupal root directory could not be located.');
+      return $messages;
+    }
+    $this->diskSpace($messages);
+    return $messages;
+  }
+
+  /**
+   * Get the Drupal root path.
+   *
+   * @return string
+   *   The Drupal root path.
+   */
+  protected function getDrupalRoot() {
+    if (!$this->drupalRoot && $this->drupalFinder->locateRoot(getcwd())) {
+      $this->drupalRoot = $this->drupalFinder->getDrupalRoot();
+    }
+    return $this->drupalRoot;
+  }
+
+  /**
+   * Get the vendor path.
+   *
+   * @return string
+   *   The vendor path.
+   */
+  protected function getVendorPath() {
+    if (!$this->vendorPath && $this->drupalFinder->locateRoot(getcwd())) {
+      $this->vendorPath = $this->drupalFinder->getVendorDir();
+    }
+    return $this->vendorPath;
+  }
+
+  /**
+   * Check if the filesystem has sufficient disk space.
+   *
+   * @param array $messages
+   *   The messages array of translatable strings.
+   */
+  protected function diskSpace(array &$messages) {
+    if ($this->areSameLogicalDisk($this->getDrupalRoot(), $this->getVendorPath())) {
+      if (disk_free_space($this->getDrupalRoot()) < static::MINIMUM_DISK_SPACE) {
+        $messages[] = $this->t('Logical disk "@root" has insufficient space. There must be at least @space megabytes free.', [
+          '@root' => $this->getDrupalRoot(),
+          '@space' => static::MINIMUM_DISK_SPACE / static::MEGABYTE_DIVISOR,
+        ]);
+      }
+      return;
+    }
+    if (disk_free_space($this->getDrupalRoot()) < static::MINIMUM_DISK_SPACE) {
+      $messages[] = $this->t('Drupal root filesystem "@root" has insufficient space. There must be at least @space megabytes free.', [
+        '@root' => $this->getDrupalRoot(),
+        '@space' => static::MINIMUM_DISK_SPACE / static::MEGABYTE_DIVISOR,
+      ]);
+    }
+    if (disk_free_space($this->getVendorPath()) < static::MINIMUM_DISK_SPACE) {
+      $messages[] = $this->t('Vendor filesystem "@vendor" has insufficient space. There must be at least @space megabytes free.', [
+        '@vendor' => $this->getVendorPath(),
+        '@space' => static::MINIMUM_DISK_SPACE / static::MEGABYTE_DIVISOR,
+      ]);
+    }
+  }
+
+  /**
+   * Determine if the root and vendor file system are the same logical disk.
+   *
+   * @param string $root
+   *   Root file path.
+   * @param string $vendor
+   *   Vendor file path.
+   *
+   * @return bool
+   *   TRUE if same file system, FALSE otherwise.
+   */
+  protected function areSameLogicalDisk($root, $vendor) {
+    $root_statistics = stat($root);
+    $vendor_statistics = stat($vendor);
+    return $root_statistics['dev'] === $vendor_statistics['dev'];
+  }
+
+}
diff --git a/src/ReadinessChecker/ReadOnlyFilesystem.php b/src/ReadinessChecker/ReadOnlyFilesystem.php
new file mode 100644
index 0000000..a71c626
--- /dev/null
+++ b/src/ReadinessChecker/ReadOnlyFilesystem.php
@@ -0,0 +1,214 @@
+<?php
+
+namespace Drupal\automatic_updates\ReadinessChecker;
+
+use Drupal\Component\Render\MarkupInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use DrupalFinder\DrupalFinder;
+use League\Flysystem\Adapter\Local;
+use League\Flysystem\Cached\CachedAdapter;
+use League\Flysystem\Cached\CacheInterface;
+use League\Flysystem\FileExistsException;
+use League\Flysystem\FileNotFoundException;
+use League\Flysystem\Filesystem;
+use League\Flysystem\FilesystemInterface;
+use Psr\Log\LoggerInterface;
+
+/**
+ * Read only filesystem checker.
+ */
+class ReadOnlyFilesystem implements ReadinessCheckerInterface {
+  use StringTranslationTrait;
+
+  /**
+   * The logger.
+   *
+   * @var \Psr\Log\LoggerInterface
+   */
+  protected $logger;
+
+  /**
+   * The core file system.
+   *
+   * @var \League\Flysystem\FilesystemInterface
+   */
+  protected $coreFileSystem;
+
+  /**
+   * The root file path.
+   *
+   * @var string
+   */
+  protected $rootPath;
+
+  /**
+   * The vendor file system.
+   *
+   * @var \League\Flysystem\FilesystemInterface
+   */
+  protected $vendorFileSystem;
+
+  /**
+   * The vendor file path.
+   *
+   * @var string
+   */
+  protected $vendorPath;
+
+  /**
+   * The drupal finder service.
+   *
+   * @var \DrupalFinder\DrupalFinder
+   */
+  protected $drupalFinder;
+
+  /**
+   * The file system cache.
+   *
+   * @var \League\Flysystem\Cached\CacheInterface
+   */
+  protected $fileSystemCache;
+
+  /**
+   * ReadOnlyFilesystem constructor.
+   *
+   * @param \Psr\Log\LoggerInterface $logger
+   *   The logger.
+   * @param \DrupalFinder\DrupalFinder $drupal_finder
+   *   The Drupal finder.
+   * @param \League\Flysystem\Cached\CacheInterface $filesystem_cache
+   *   The filesystem cache.
+   */
+  public function __construct(LoggerInterface $logger, DrupalFinder $drupal_finder, CacheInterface $filesystem_cache) {
+    $this->logger = $logger;
+    $this->drupalFinder = $drupal_finder;
+    $this->fileSystemCache = $filesystem_cache;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function run() {
+    $messages = [];
+    if (!$this->getCoreFileSystem() || !$this->getCoreFileSystem()->has('core.services.yml')) {
+      $messages[] = $this->t('The public web directory could not be located.');
+      return $messages;
+    }
+    $this->readOnly($messages);
+    return $messages;
+  }
+
+  /**
+   * Get the core filesystem.
+   *
+   * @return \League\Flysystem\Filesystem|\League\Flysystem\FilesystemInterface
+   *   The core filesystem.
+   */
+  protected function getCoreFileSystem() {
+    if (!$this->coreFileSystem && $this->drupalFinder->locateRoot(getcwd())) {
+      $this->rootPath = $this->drupalFinder->getDrupalRoot();
+      $this->coreFileSystem = new Filesystem(new CachedAdapter(new Local($this->rootPath . '/core'), $this->fileSystemCache));
+    }
+    return $this->coreFileSystem;
+  }
+
+  /**
+   * Get the vendor file system.
+   *
+   * @return \League\Flysystem\Filesystem|\League\Flysystem\FilesystemInterface
+   *   The vendor filesystem.
+   */
+  protected function getVendorFileSystem() {
+    if (!$this->vendorFileSystem && $this->drupalFinder->locateRoot(getcwd())) {
+      $this->vendorPath = $this->drupalFinder->getVendorDir();
+      $this->vendorFileSystem = new Filesystem(new CachedAdapter(new Local($this->vendorPath), $this->fileSystemCache));
+    }
+    return $this->vendorFileSystem;
+  }
+
+  /**
+   * Check if the filesystem is read only.
+   *
+   * @param array $messages
+   *   The messages array of translatable strings.
+   */
+  protected function readOnly(array &$messages) {
+    // Disable default error handling as rename of files on read only file
+    // systems causes PHP errors.
+    restore_error_handler();
+    try {
+      if ($this->areSameLogicalDisk($this->rootPath, $this->vendorPath)) {
+        $error = $this->t('Logical disk "@file_system" is read only. Updates to Drupal cannot be applied against a read only file system.', ['@file_system' => $this->rootPath]);
+        $this->doReadOnlyCheck($this->getCoreFileSystem(), 'core.services.yml', $messages, $error);
+      }
+      else {
+        $error = $this->t('Drupal core filesystem "@file_system" is read only. Updates to Drupal core cannot be applied against a read only file system.', ['@file_system' => $this->rootPath . '/core']);
+        $this->doReadOnlyCheck($this->getCoreFileSystem(), 'core.services.yml', $messages, $error);
+        $error = $this->t('Vendor filesystem "@file_system" is read only. Updates to the site\'s code base cannot be applied against a read only file system.', ['@file_system' => $this->vendorPath]);
+        $this->doReadOnlyCheck($this->getVendorFileSystem(), 'composer/LICENSE', $messages, $error);
+      }
+    }
+    catch (\LogicException $exception) {
+      $this->logger->error($exception->getMessage());
+      $messages[] = $this->t('During read only check, a logic exception was encountered');
+    }
+    // Re-enable the default error handling.
+    set_error_handler('_drupal_error_handler');
+  }
+
+  /**
+   * Do the read only check.
+   *
+   * @param \League\Flysystem\FilesystemInterface $filesystem
+   *   The filesystem to test.
+   * @param string $file
+   *   The file path.
+   * @param array $messages
+   *   The messages array of translatable strings.
+   * @param \Drupal\Component\Render\MarkupInterface $message
+   *   The error message to add if the file is read only.
+   */
+  protected function doReadOnlyCheck(FilesystemInterface $filesystem, $file, array &$messages, MarkupInterface $message) {
+    try {
+      if ($filesystem && $filesystem->rename($file, "$file.moved")) {
+        // Move it back after moving it.
+        $filesystem->rename("$file.moved", $file);
+      }
+      else {
+        $this->logger->error($message);
+        $messages[] = $message;
+      }
+    }
+    catch (FileExistsException $exception) {
+      $this->logger->error($exception->getMessage());
+      $messages[] = $this->t('File already exists at path: @file', ['@file' => $exception->getPath()]);
+    }
+    catch (FileNotFoundException $exception) {
+      $this->logger->error($exception->getMessage());
+      $messages[] = $this->t('File not found at path: @file', ['@file' => $exception->getPath()]);
+    }
+    // Catching throwable because rename triggers error in some cases.
+    catch (\Throwable $throwable) {
+      $this->logger->error($throwable->getMessage());
+      $messages[] = $throwable->getMessage();
+    }
+  }
+
+  /**
+   * Determine if the root and vendor file system are the same logical disk.
+   *
+   * @param string $root
+   *   Root file path.
+   * @param string $vendor
+   *   Vendor file path.
+   *
+   * @return bool
+   *   TRUE if same file system, FALSE otherwise.
+   */
+  protected function areSameLogicalDisk($root, $vendor) {
+    $root_statistics = stat($root);
+    $vendor_statistics = stat($vendor);
+    return $root_statistics['dev'] === $vendor_statistics['dev'];
+  }
+
+}
diff --git a/src/ReadinessChecker/ReadinessCheckerInterface.php b/src/ReadinessChecker/ReadinessCheckerInterface.php
new file mode 100644
index 0000000..11fe60a
--- /dev/null
+++ b/src/ReadinessChecker/ReadinessCheckerInterface.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Drupal\automatic_updates\ReadinessChecker;
+
+/**
+ * Interface for objects capable of readiness checking.
+ */
+interface ReadinessCheckerInterface {
+
+  /**
+   * Run check.
+   *
+   * @return array
+   *   An array of translatable strings.
+   */
+  public function run();
+
+}
diff --git a/src/ReadinessChecker/ReadinessCheckerManager.php b/src/ReadinessChecker/ReadinessCheckerManager.php
new file mode 100644
index 0000000..21f33e5
--- /dev/null
+++ b/src/ReadinessChecker/ReadinessCheckerManager.php
@@ -0,0 +1,111 @@
+<?php
+
+namespace Drupal\automatic_updates\ReadinessChecker;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\State\StateInterface;
+
+/**
+ * Defines a chained readiness checker implementation combining multiple checks.
+ */
+class ReadinessCheckerManager implements ReadinessCheckerManagerInterface {
+
+  /**
+   * The key/value storage.
+   *
+   * @var \Drupal\Core\State\StateInterface
+   */
+  protected $keyValue;
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * An unsorted array of arrays of active checkers.
+   *
+   * An associative array. The keys are integers that indicate priority. Values
+   * are arrays of ReadinessCheckerInterface objects.
+   *
+   * @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerInterface[][]
+   */
+  protected $checkers = [];
+
+  /**
+   * ReadinessCheckerManager constructor.
+   *
+   * @param \Drupal\Core\State\StateInterface $key_value
+   *   The key/value service.
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   */
+  public function __construct(StateInterface $key_value, ConfigFactoryInterface $config_factory) {
+    $this->keyValue = $key_value;
+    $this->configFactory = $config_factory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addChecker(ReadinessCheckerInterface $checker, $priority = 0) {
+    $this->checkers[$priority][] = $checker;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function run() {
+    $messages = [];
+    if (!$this->isEnabled()) {
+      return $messages;
+    }
+    foreach ($this->getSortedCheckers() as $checker) {
+      $messages = array_merge($messages, $checker->run());
+    }
+    $this->keyValue->set('readiness_check_results', $messages);
+    $this->keyValue->set('readiness_check_timestamp', \Drupal::time()->getCurrentTime());
+    return $messages;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function results() {
+    return $this->keyValue->get('readiness_check_results', []);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function timestamp() {
+    return $this->keyValue->get('readiness_check_timestamp', 0);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isEnabled() {
+    return $this->configFactory->get('automatic_updates.settings')->get('enable_readiness_checks');
+  }
+
+  /**
+   * Sorts checkers according to priority.
+   *
+   * @return \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerInterface[]
+   *   A sorted array of checker objects.
+   */
+  protected function getSortedCheckers() {
+    $sorted = [];
+    krsort($this->checkers);
+
+    foreach ($this->checkers as $checkers) {
+      $sorted = array_merge($sorted, $checkers);
+    }
+    return $sorted;
+  }
+
+}
diff --git a/src/ReadinessChecker/ReadinessCheckerManagerInterface.php b/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
new file mode 100644
index 0000000..05870f1
--- /dev/null
+++ b/src/ReadinessChecker/ReadinessCheckerManagerInterface.php
@@ -0,0 +1,59 @@
+<?php
+
+namespace Drupal\automatic_updates\ReadinessChecker;
+
+/**
+ * Readiness checker manager interface.
+ */
+interface ReadinessCheckerManagerInterface {
+
+  /**
+   * Last checked ago warning (in seconds).
+   */
+  const LAST_CHECKED_WARNING = 3600 * 24;
+
+  /**
+   * Appends a checker to the checker chain.
+   *
+   * @param \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerInterface $checker
+   *   The checker interface to be appended to the checker chain.
+   * @param int $priority
+   *   The priority of the checker being added.
+   *
+   * @return $this
+   */
+  public function addChecker(ReadinessCheckerInterface $checker, $priority);
+
+  /**
+   * Run checks.
+   *
+   * @return array
+   *   An array of translatable strings.
+   */
+  public function run();
+
+  /**
+   * Get results of most recent run.
+   *
+   * @return array|null
+   *   An array of translatable strings.
+   */
+  public function results();
+
+  /**
+   * Get timestamp of most recent run.
+   *
+   * @return int
+   *   A unix timestamp of most recent completed run.
+   */
+  public function timestamp();
+
+  /**
+   * Determine if readiness checks is enabled.
+   *
+   * @return bool
+   *   TRUE if enabled, otherwise FALSE.
+   */
+  public function isEnabled();
+
+}
diff --git a/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php b/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
new file mode 100644
index 0000000..5e289e3
--- /dev/null
+++ b/tests/src/Kernel/ReadinessChecker/DiskSpaceTest.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace Drupal\Tests\automatic_updates\Kernel\ReadinessChecker;
+
+use Drupal\automatic_updates\ReadinessChecker\DiskSpace;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests disk space readiness checking.
+ *
+ * @group automatic_updates
+ */
+class DiskSpaceTest extends KernelTestBase {
+  use StringTranslationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'automatic_updates',
+  ];
+
+  /**
+   * Tests the functionality of disk space readiness checks.
+   */
+  public function testDiskSpace() {
+    // No disk space issues.
+    $disk_space = new DiskSpace($this->container->get('logger.channel.automatic_updates'), $this->container->get('automatic_updates.drupal_finder'));
+    $messages = $disk_space->run();
+    $this->assertEmpty($messages);
+
+    // Out of space.
+    $disk_space = new TestDiskSpace($this->container->get('logger.channel.automatic_updates'), $this->container->get('automatic_updates.drupal_finder'));
+    $messages = $disk_space->run();
+    $this->assertCount(1, $messages);
+
+    // Out of space not the same logical disk.
+    $disk_space = new TestDiskSpaceNonSameDisk($this->container->get('logger.channel.automatic_updates'), $this->container->get('automatic_updates.drupal_finder'));
+    $messages = $disk_space->run();
+    $this->assertCount(2, $messages);
+  }
+
+}
+
+/**
+ * Class TestDiskSpace.
+ */
+class TestDiskSpace extends DiskSpace {
+
+  /**
+   * Override the default free disk space minimum to an insanely high number.
+   */
+  const MINIMUM_DISK_SPACE = 99999999999999999999999999999999999999999999999999;
+
+}
+
+/**
+ * Class TestDiskSpaceNonSameDisk.
+ */
+class TestDiskSpaceNonSameDisk extends TestDiskSpace {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function areSameLogicalDisk($root, $vendor) {
+    return FALSE;
+  }
+
+}
diff --git a/tests/src/Kernel/ReadinessChecker/ReadOnlyTest.php b/tests/src/Kernel/ReadinessChecker/ReadOnlyTest.php
new file mode 100644
index 0000000..f95fc7b
--- /dev/null
+++ b/tests/src/Kernel/ReadinessChecker/ReadOnlyTest.php
@@ -0,0 +1,119 @@
+<?php
+
+namespace Drupal\Tests\automatic_updates\Kernel\ReadinessChecker;
+
+use Drupal\automatic_updates\ReadinessChecker\ReadOnlyFilesystem;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\KernelTests\KernelTestBase;
+use DrupalFinder\DrupalFinder;
+use League\Flysystem\Cached\CacheInterface;
+use League\Flysystem\FileExistsException;
+use League\Flysystem\FileNotFoundException;
+use League\Flysystem\Filesystem;
+use Psr\Log\LoggerInterface;
+
+/**
+ * Tests read only readiness checking.
+ *
+ * @group automatic_updates
+ */
+class ReadOnlyTest extends KernelTestBase {
+  use StringTranslationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'automatic_updates',
+  ];
+
+  /**
+   * Tests the functionality of read only filesystem readiness checks.
+   */
+  public function testReadOnly() {
+    $filesystem = $this->createMock(Filesystem::class);
+    $filesystem->expects($this->any())
+      ->method('has')
+      ->withAnyParameters()
+      ->will($this->onConsecutiveCalls(FALSE, TRUE, TRUE, TRUE));
+    $filesystem->expects($this->any())
+      ->method('rename')
+      ->withAnyParameters()
+      ->will($this->onConsecutiveCalls(
+        FALSE,
+        FALSE,
+        FALSE,
+        $this->throwException(new FileExistsException('core.services.yml')),
+        $this->throwException(new FileNotFoundException('composer/LICENSE'))
+      )
+    );
+
+    $readonly = $this->getMockBuilder(TestReadOnlyFilesystem::class)
+      ->setConstructorArgs([
+        $this->createMock(LoggerInterface::class),
+        new DrupalFinder(),
+        $this->createMock(CacheInterface::class),
+      ])
+      ->setMethods([
+        'getCoreFileSystem',
+        'getVendorFileSystem',
+        'areSameLogicalDisk',
+      ])
+      ->getMock();
+    $readonly->method('getCoreFileSystem')
+      ->willReturn($filesystem);
+    $readonly->method('getVendorFileSystem')
+      ->willReturn($filesystem);
+    $readonly->expects($this->any())
+      ->method('areSameLogicalDisk')
+      ->withAnyParameters()
+      ->will($this->onConsecutiveCalls(
+        TRUE,
+        FALSE,
+        FALSE,
+      )
+    );
+
+    // Test can't locate drupal.
+    $messages = $readonly->run();
+    $this->assertEquals([$this->t('The public web directory could not be located.')], $messages);
+
+    // Test same logical disk.
+    $expected_messages = [];
+    $expected_messages[] = $this->t('Logical disk "/var/www/html" is read only. Updates to Drupal cannot be applied against a read only file system.');
+    $messages = $readonly->run();
+    $this->assertEquals($expected_messages, $messages);
+
+    // Test read-only.
+    $expected_messages = [];
+    $expected_messages[] = $this->t('Drupal core filesystem "/var/www/html/core" is read only. Updates to Drupal core cannot be applied against a read only file system.');
+    $expected_messages[] = $this->t('Vendor filesystem "/var/www/html/vendor" is read only. Updates to the site\'s code base cannot be applied against a read only file system.');
+    $messages = $readonly->run();
+    $this->assertEquals($expected_messages, $messages);
+
+    // Test FileExistsException and FileNotFoundException.
+    $expected_messages = [];
+    $expected_messages[] = $this->t('File already exists at path: core.services.yml');
+    $expected_messages[] = $this->t('File not found at path: composer/LICENSE');
+    $messages = $readonly->run();
+    $this->assertEquals($expected_messages, $messages);
+  }
+
+}
+
+/**
+ * Class TestReadOnlyFilesystem.
+ */
+class TestReadOnlyFilesystem extends ReadOnlyFilesystem {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $rootPath = '/var/www/html';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $vendorPath = '/var/www/html/vendor';
+
+}
diff --git a/tests/src/Kernel/ReadinessChecker/ReadinessCheckerTest.php b/tests/src/Kernel/ReadinessChecker/ReadinessCheckerTest.php
new file mode 100644
index 0000000..0e5fb95
--- /dev/null
+++ b/tests/src/Kernel/ReadinessChecker/ReadinessCheckerTest.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Drupal\Tests\automatic_updates\Kernel;
+
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests automatic updates readiness checking.
+ *
+ * @group automatic_updates
+ */
+class ReadinessCheckerTest extends KernelTestBase {
+  use StringTranslationTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'automatic_updates',
+  ];
+
+  /**
+   * Tests the functionality of readiness checks.
+   */
+  public function testReadinessChecker() {
+    /** @var \Drupal\automatic_updates\ReadinessChecker\ReadinessCheckerManagerInterface $checker */
+    $checker = $this->container->get('automatic_updates.readiness_checker');
+    $this->assertEmpty($checker->run());
+  }
+
+}