How to change mysql root password.

I receive a lots of queries on how to change the mysql server root password under Linux/Ubuntu...
On Googling I found the following answer for the query.

You need to mysqladmin command which is a client for performing administrative operations. You can use it to check the server’s configuration and current status, to create and drop databases, change mysql root password and more.

If you are setting a root password first time, use any one of the following command syntax:
mysqladmin password “NEW-PASSWORD“
OR
mysqladmin -u root password “NEW-PASSWORD“
OR
mysqladmin -u root -h localhost password “NEW-PASSWORD“

To set password to d3s9cXq, enter:
# mysqladmin -u root password "d3s9cXq"

Please note that if the NEW-PASSWORD value contains spaces or other characters that are special to your command interpreter, you need to enclose it within quotes. Thus, the next time you invoke mysqladmin (or any other client program such as mysql) using the same account, you will need to specify the new password. So to login as root, enter the command:
# mysql -u root -p
OR
# mysql -h localhost -u root -p

Where,

• -u root: Specify username
• -p : Prompt for password

If you would like to change current password d3s9cXq to OlzzYs$qz, enter the following command:
# mysqladmin -u root -p password "OlzzYs$qz"
Output:

Enter password: <enter old password>

Thanks to CyberCiti for providing this.