Step by step:
- move /srv/www/nextcloud/data/admin folder to the backup location
- move /srv/www/nextcloud/config/config.php to the backup location
- login to the mysql as a root user “mysql -u root”
- apply commands:
DROP DATABASE nextcloud;
DROP USER ‘nextcloud’@‘localhost’;
DROP USER ‘nextcloud’@‘127.0.0.1’; - run the script “nextcloud_install” and follow instruction