Typically, when you install MySQL on Ubuntu, it asks you for a root password which you can then use to log into the database. It seems that MariaDB uses a plugin instead to authenticate the root user. This means that the only way to log into MariaDB by default as root is locally with sudo mysql -u root In order to give the root user a password and login the “traditional” way (which includes remote access via a tunnel) you have to do the following.

1. Log into MariaDB as the Root user

   sudo mysql -u root
   

2. Disable the Auth Plugin

   use mysql;
   update user set plugin='' where User='root';
   

3. Create a password for the root user

   grant all privileges on *.* to 'root'@'127.0.0.1' identified by '$STRONG_PASSWORD';
   flush privileges;
   

4. Restart MariaDB

   sudo service mysql Restart
   

You can now access the root account with a password, and also over an SSH tunnel remotely.