Exemple : Field 'username'
Welcome To Drupal 8
Drupal is a CMS (Content Management System) open-source written in PHP. Drupl 8 is the latest version of Drupal successor of Drupal 7 popular for its security, flexibility and scalability, used on the complex high traffic web applications as well as small showcase sites. Drupal 8 is comes with over 200 new features and improvements including native full responsive support, multilingual support, REST Full web service. Drupal 8 was created in PHP using Symfony 2 Framework and TWIG templating system.
This web site is a set of tutorials help to new Drupal 8 developers and persons who want to be a Drupal 8 developer or a webmaster. The level of the tutorials are start from very basic (beginners) and can be very complex (Experts). I hope the site is useful for you and you are welcome to share your knowledge, ideas and experience. Thank you.
Store data on session.
$session = new \Symfony\Component\HttpFoundation\Session\Session();
$session->set('var_name', $session->get('var_name',0) + 1);
The solution is:
ssh-keygen -R <host>
ssh-keygen -R 127.0.0.1
ssh-keygen -R domainname.com
There are several ways to do that.