For MariaDB by default the root user exist on the database but its no longer usable over phpmyadmin. Its also not advisable for you to use the root user in light of security reasons unless you accept the security risk.
For us to use our database we need to create another user to the database so that we can connect to it on phpmyadmin. The following command will create the user on the database and it will also show all users created on the database itself.
firstname.lastname@example.org:/# mysql -u root Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 2977 Server version: 10.0.33-MariaDB-0ubuntu0.16.04.1 Ubuntu 16.04 Copyright (c) 2000, 2017, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MariaDB [(none)]> CREATE USER 'database_user'@'localhost' IDENTIFIED BY 'database_password';GRANT ALL PRIVILEGES ON *.* TO 'database_user'@'localhost' WITH GRANT OPTION;FLUSH PRIVILEGES;SELECT User FROM mysql.user; This will make the user we need with the logins ready. +---------------+ | User | +---------------+ | database_user | | root | +---------------+