MySQL Change root Password

Method #1: Use mysqladmin command to change root password

If you have never set a root password for MySQL server, the server does not require a password at all for connecting as root. To setup root password for first time, use mysqladmin command at shell prompt as follows:
$ mysqladmin -u root password NEWPASSWORD

However, if you want to change (or update) a root password, then you need to use the following command:

$ mysqladmin -u root -p'oldpassword' password newpass

For example, If the old password is abc, you can set the new password to 123456, enter:
$ mysqladmin -u root -p'abc' password '123456'

Note:123456 password is used for demonstration purpose only. You must select a strong password. It is an important protection to help you have safer MySQL database transactions.
Sample live session from my home server using mysqladmin


Fig.01: mysqladmin command in action
How do I verify that the new password is working or not?

Use the following mysql command:

mysql -u root -p'123456' db-name-here

OR

mysql -u root -p'123456' -e 'show databases;'
A note about changing MySQL password for other users

To change a normal user password you need to type the following command. In this example, change the password for nixcraft mysql user:
$ mysqladmin -u nixcraft -p'old-password' password new-password

Method #2: Changing MySQL root user password using mysql command

This is an another method. MySQL stores username and passwords in user table inside MySQL database. You can directly update or change the password using the following method for user called nixcraft:
Login to mysql server, type the following command at shell prompt:
$ mysql -u root -p
or
if there is no password of root user
Use $mysql

Use mysql database (type command at mysql> prompt):

mysql> use mysql;

Change password for user nixcraft, enter:
mysql> update user set password=PASSWORD("NEWPASSWORD") where User='nixcraft';

Finally, reload the privileges:
mysql> flush privileges;
mysql> quit