This happens when your session.save_handler PHP parameter is set to some another session storage than files (for example, redis, memcached, and so on). This is a known issue we’re working to resolve.
Solutions:
Locate php.ini
Locate php.ini
by entering the following command:
php -i | grep "Loaded Configuration File"
Typical locations follow:
- Ubuntu: /etc/php5/cli/php.ini
- CentOS: /etc/php.ini
Workaround
- As a user with root privileges, open php.ini in a text editor.
- Locate session.save_handler
- Set it in any of the following ways:
To comment it out:
;session.save_path = <path>
To set it to a file system path:
session.save_handler = files
References:
https://devdocs.magento.com/guides/v2.1/install-gde/trouble/php/tshoot_session.html
https://github.com/magento/magento2/issues/5319
I hope this will help