MariaDB installed without password prompt

sudo mysql -u root

[mysql] use mysql;
[mysql] update user set plugin='' where User='root';
[mysql] flush privileges;
[mysql] \q

This needs to be followed by following command

# mysql_secure_installation

it is common for root to have password-less access if accessing from localhost, I recommend this setting to be left alone.

I also recommend that you create a user with less permissions and allow that user to login remotely.

create user my_admin identified by '12345';
create database my_database;
grant all on my_database.* to my_admin;

This way you have a little more security.

If you do need to connect as root from a tool like workbench, you can configure those tools to create an ssh tunnel and connect to the database as localhost.

Starting with MariaDB 10.4 root@localhost account is created with the ability to use two authentication plugins:

• First, it is configured to try to use the unix_socket authentication plugin. This allows the root@localhost user to login without a password via the local Unix socket file defined by the socket system variable, as long as the login is attempted from a process owned by the operating system root user account.
• Second, if authentication fails with the unix_socket authentication plugin, then it is configured to try to use the mysql_native_password authentication plugin. However, an invalid password is initially set, so in order to authenticate this way, a password must be set with SET PASSWORD.

That is why you don't need a password to login on a fresh install.

But then another quote:

When the plugin column is empty, MariaDB defaults to authenticating accounts with either the mysql_native_password or the mysql_old_password plugins. It decides which based on the hash used in the value for the Password column. When there's no password set or when the 4.1 password hash is used, (which is 41 characters long), MariaDB uses the mysql_native_password plugin. The mysql_old_password plugin is used with pre-4.1 password hashes, (which are 16 characters long).

So setting plugin = '' will force it to use password based authentication. Make sure you set a password before that.

sudo mysql -u root

[mysql] use mysql;
[mysql] update user set plugin='' where User='root';
[mysql] flush privileges;
[mysql] \q