drupal/core/profiles/standard/standard.install

<?php
/**
 * @file
 * Install, update and uninstall functions for the standard installation profile.
 */

use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
use Drupal\user\Entity\User;
use Drupal\user\RoleInterface;

/**
 * Implements hook_install().
 *
 * Perform actions to set up the site for this profile.
 *
 * @see system_install()
 */
function standard_install() {
  // Set front page to "node".
  \Drupal::configFactory()->getEditable('system.site')->set('page.front', '/node')->save(TRUE);

  // Allow visitor account creation with administrative approval.
  $user_settings = \Drupal::configFactory()->getEditable('user.settings');
  $user_settings->set('register', USER_REGISTER_VISITORS_ADMINISTRATIVE_APPROVAL)->save(TRUE);

  // Enable default permissions for system roles.
  user_role_grant_permissions(RoleInterface::ANONYMOUS_ID, array('access comments'));
  user_role_grant_permissions(RoleInterface::AUTHENTICATED_ID, array('access comments', 'post comments', 'skip comment approval'));

  // Assign user 1 the "administrator" role.
  $user = User::load(1);
  $user->roles[] = 'administrator';
  $user->save();

  // Enable the Contact link in the footer menu.
  /** @var \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager */
  $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
  $menu_link_manager->updateDefinition('contact.site_page', array('enabled' => TRUE));

  user_role_grant_permissions(RoleInterface::ANONYMOUS_ID, array('access site-wide contact form'));
  user_role_grant_permissions(RoleInterface::AUTHENTICATED_ID, array('access site-wide contact form'));

  // Allow authenticated users to use shortcuts.
  user_role_grant_permissions(RoleInterface::AUTHENTICATED_ID, array('access shortcuts'));

  // Populate the default shortcut set.
  $shortcut = entity_create('shortcut', array(
    'shortcut_set' => 'default',
    'title' => t('Add content'),
    'weight' => -20,
    'link' => array('uri' => 'internal:/node/add'),
  ));
  $shortcut->save();

  $shortcut = entity_create('shortcut', array(
    'shortcut_set' => 'default',
    'title' => t('All content'),
    'weight' => -19,
    'link' => array('uri' => 'internal:/admin/content'),
  ));
  $shortcut->save();

  // Enable the admin theme.
  \Drupal::configFactory()->getEditable('node.settings')->set('use_admin_theme', TRUE)->save(TRUE);
}