It shouldn’t happen, but it does: I forgot my MySQL root password. Resetting is rather simple. Stop the running mysqld instance and restart it in safe mode:

# mysqld_safe --skip-grant-tables &

You can now log in as root without a password:

# mysql --user=root
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MariaDB connection id is 1
Server version: 5.5.35-MariaDB MariaDB Server

Copyright (c) 2000, 2013, Oracle, Monty Program Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> update mysql.user set Password=PASSWORD('your_new_root_password') where User='root';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0

MariaDB [(none)]> flush privileges;
Query OK, 0 rows affected (0.01 sec)

MariaDB [(none)]> quit;
Bye
# pkill mysqld

Don’t forget restart the mysql server and clear ~/.mysql_history afterwards!