hi

need to reset mysql root password after migra?

kill mysql procs

start mysql with options

/usr/sbin/mysqld --skip-networking --skip-grant-tables

now we login with no password:

mysql -u root

now we update the password:

UPDATE mysql.user SET Password=PASSWORD('yournewpassword') WHERE User='root';

kill mysql procs

start mysql via initscript

some debian specific:
after setting the root password you need to create or update the debian-sys-maint user

CREATE USER 'debian-sys-maint'@'localhost' IDENTIFIED BY 'yourpassword';

GRANT ALL PRIVILEGES ON *.* TO 'debian-sys-maint'@'localhost' WITH GRANT OPTION;

UPDATE mysql.user SET Password=PASSWORD('yourpassword') WHERE User='debian-sys-maint';

have fun