MySQL: How to reset or change the MySQL root password?

How do I change the MySQL root password and username in ubuntu server? Do I need to stop the mysql service before setting any changes?

I have a phpmyadmin setup as well, will phpmyadmin get updated automatically?

Solution

Set / change / reset the MySQL root password on Ubuntu Linux. Enter the following lines in your terminal.

Stop the MySQL Server: sudo /etc/init.d/mysql stop
(In some cases, if /var/run/mysqld doesn't exist, you have to create it at first: sudo mkdir -v /var/run/mysqld && sudo chown mysql /var/run/mysqld
Start the mysqld configuration: sudo mysqld --skip-grant-tables &
Login to MySQL as root: mysql -u root mysql
Replace YOURNEWPASSWORD with your new password:

For MySQL < 8.0

UPDATE mysql.user SET Password = PASSWORD('YOURNEWPASSWORD') WHERE User = 'root';
FLUSH PRIVILEGES;

If your MySQL uses new auth plugin, you will need to use: update user set plugin="mysql_native_password" where User='root'; before flushing privileges.

Note: on some versions, if password column doesn't exist, you may want to try:
UPDATE user SET authentication_string=password('YOURNEWPASSWORD') WHERE user='root';

Note: This method is not regarded as the most secure way of resetting the password, however, it works.

For MySQL >= 8.0

FLUSH PRIVILEGES;
ALTER USER 'root'@'localhost' IDENTIFIED BY 'YOURNEWPASSWORD';
FLUSH PRIVILEGES;

Last step:

As noted in comments by @lambart, you might need to kill the temporary password-less mysql process that you started, i.e. sudo killall -9 mysqld and then start normal daemon: sudo service mysql start

References: