How to completely delete MySql in Linux

First, use rpm-Qa | grep MySQL to find out all MySQL version packages and unmount them one by one. Then, remember to back up all files in the var/lib/MySQL directory as tar and copy them to the root directory. switch to the "Find/-name MySQL" directory and find all MySQL files. Delete All The sudo Rm-r files one by one. You can find the "Find/-name mysqld" file and the file will be completely gone..
How to change the MySQL Root Password:
1. Modify MySQL Logon Settings:
# Vi/etc/My. CNF
In the [mysqld] section, add skip-grant-tables.
For example:
[Mysqld]
Datadir =/var/lib/MySQL
Socket =/var/lib/MySQL. Sock
Skip-name-resolve
Skip-grant-tables
Save and exit VI.

3. Restart mysqld
#/Etc/init. d/mysqld restart
Stopping MYSQL: [OK]
Starting MYSQL: [OK]

4. log on to and modify the MySQL Root Password
#/Usr/bin/MySQL
Welcome to the MySQL monitor. commands end with; or \ G.
Your MySQL connection ID is 3 to server version: 3.23.56

Type 'help; 'or' \ H' for help. Type '\ C' to clear the buffer.

Mysql> use MySQL;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with-

Database changed
Mysql> Update user SET Password = PASSWORD ('new-password') where user = 'root ';
Query OK, 0 rows affected (0.00 Sec)
Rows matched: 2 changed: 0 Warnings: 0

Mysql> flush privileges;
Query OK, 0 rows affected (0.01 Sec)

Mysql> quit
Bye

5. Modify the MySQL Logon Settings.
# Vi/etc/My. CNF
Delete the skip-grant-tables added to the [mysqld] section.
Save and exit VI.

6. Restart mysqld
#/Etc/init. d/mysqld restart
Stopping MYSQL: [OK]
Starting MYSQL: [OK]

7. restore the normal working status of the server
Perform the inverse operation in step 1. Restore the server's working status.

Source: http://bbs.chinaunix.net/thread-820187-1-1.html