php_network_getaddresses: getaddrinfo for mariadb failed: Name does not resolve

mysqli_sql_exception:
php_network_getaddresses: getaddrinfo for mariadb failed: Name does not resolve

  at /var/www/html/legremlin.org/libraries/vendor/joomla/database/src/Mysqli/MysqliDriver.php:268
  at mysqli->real_connect('mariadb', 'legremlin_user', object(SensitiveParameterValue), null, 3306, null, 0)
     (/var/www/html/legremlin.org/libraries/vendor/joomla/database/src/Mysqli/MysqliDriver.php:268)
  at Joomla\Database\Mysqli\MysqliDriver->connect()
     (/var/www/html/legremlin.org/libraries/vendor/joomla/database/src/DatabaseDriver.php:1854)
  at Joomla\Database\DatabaseDriver->setQuery(object(MysqliQuery))
     (/var/www/html/legremlin.org/libraries/src/Menu/SiteMenu.php:166)
  at Joomla\CMS\Menu\SiteMenu->Joomla\CMS\Menu\{closure}()
     (/var/www/html/legremlin.org/libraries/src/Cache/Controller/CallbackController.php:52)
  at Joomla\CMS\Cache\Controller\CallbackController->get(object(Closure), array(), 'd17e8e13b99b4d9bf23a7d0b83a466c3', false)
     (/var/www/html/legremlin.org/libraries/src/Menu/SiteMenu.php:179)
  at Joomla\CMS\Menu\SiteMenu->load()
     (/var/www/html/legremlin.org/libraries/src/Menu/AbstractMenu.php:323)
  at Joomla\CMS\Menu\AbstractMenu->getMenu()
     (/var/www/html/legremlin.org/libraries/src/Menu/AbstractMenu.php:160)
  at Joomla\CMS\Menu\AbstractMenu->getItem(null)
     (/var/www/html/legremlin.org/libraries/src/Application/SiteApplication.php:412)
  at Joomla\CMS\Application\SiteApplication->getTemplate(true)
     (/var/www/html/legremlin.org/libraries/src/Error/Renderer/HtmlRenderer.php:50)
  at Joomla\CMS\Error\Renderer\HtmlRenderer->render(object(RuntimeException))
     (/var/www/html/legremlin.org/libraries/src/Exception/ExceptionHandler.php:121)
  at Joomla\CMS\Exception\ExceptionHandler::render(object(RuntimeException))
     (/var/www/html/legremlin.org/libraries/src/Exception/ExceptionHandler.php:72)
  at Joomla\CMS\Exception\ExceptionHandler::handleException(object(RuntimeException))
     (/var/www/html/legremlin.org/libraries/src/Application/CMSApplication.php:323)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/var/www/html/legremlin.org/includes/app.php:61)
  at require_once('/var/www/html/legremlin.org/includes/app.php')
     (/var/www/html/legremlin.org/index.php:32)                

RuntimeException:
Failed to start the session because headers have already been sent by "/var/www/html/legremlin.org/libraries/vendor/joomla/uri/src/UriHelper.php" at line 36.

  at /var/www/html/legremlin.org/libraries/vendor/joomla/session/src/Storage/NativeStorage.php:473
  at Joomla\Session\Storage\NativeStorage->start()
     (/var/www/html/legremlin.org/libraries/src/Session/Storage/JoomlaStorage.php:295)
  at Joomla\CMS\Session\Storage\JoomlaStorage->start()
     (/var/www/html/legremlin.org/libraries/vendor/joomla/session/src/Session.php:406)
  at Joomla\Session\Session->start()
     (/var/www/html/legremlin.org/libraries/vendor/joomla/session/src/Session.php:333)
  at Joomla\Session\Session->has('user')
     (/var/www/html/legremlin.org/libraries/src/Session/Session.php:191)
  at Joomla\CMS\Session\Session->get('user')
     (/var/www/html/legremlin.org/libraries/src/Factory.php:334)
  at Joomla\CMS\Factory::getUser()
     (/var/www/html/legremlin.org/libraries/src/Application/SiteApplication.php:552)
  at Joomla\CMS\Application\SiteApplication->initialiseApp()
     (/var/www/html/legremlin.org/libraries/src/Application/SiteApplication.php:218)
  at Joomla\CMS\Application\SiteApplication->doExecute()
     (/var/www/html/legremlin.org/libraries/src/Application/CMSApplication.php:294)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/var/www/html/legremlin.org/includes/app.php:61)
  at require_once('/var/www/html/legremlin.org/includes/app.php')
     (/var/www/html/legremlin.org/index.php:32)