Reinstalling MySQL on CentOS/Redhat 6

Some time we faces issues with MySQL installation on Linux machine. If we simply remove MySQL packages and re-install doesn’t fixes the issue, in that case old settings may still exists on server which again affects new install. In that case first uninstall MySQL completely from system and erase all settings of old install. To do the same follow the below settings.

Note: Please do not use below steps if MySQL have any running databases.

Step 1: Uninstall MySQL Packages
First uninstall all the MySQL packages installed on your server

# yum remove mysql mysql-server

Step 2: Romove MySQL Directory
Now we need to remove MySQL data directory from system which by default exists at/var/lib/mysql. If you didn’t find this, It may be changed to some other place, which you can find in my.cnf file with variable datadir. Delete the /var/lib/mysql directory from system but we prefer to rename it to keep a backup of existing files.

# mv /var/lib/mysql /var/lib/mysql_old_backup

Step 3: Install MySQL Packages Again
After removing MySQL completely, install it again using yum package manager, It will re create mysql directory under /var/lib/.

# yum install mysql mysql-server

After completing above three steps, now you have a fresh MySQL install on your system with new settings.

Step 4: Set MySQL Passwords
Set passwords for the MySQL root account:

mysql_secure_installation

[root@server1 tmp]# mysql_secure_installation

NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MySQL
      SERVERS IN PRODUCTION USE!  PLEASE READ EACH STEP CAREFULLY!

In order to log into MySQL to secure it, we'll need the current
password for the root user.  If you've just installed MySQL, and
you haven't set the root password yet, the password will be blank,
so you should just press enter here.

Enter current password for root (enter for none):
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MySQL

root user without the proper authorisation.

Set root password? [Y/n] <-- ENTER
New password: <-- yourrootsqlpassword
Re-enter new password: <-- yourrootsqlpassword
Password updated successfully!
Reloading privilege tables..
 ... Success!

By default, a MySQL installation has an anonymous user, allowing anyone
to log into MySQL without having to have a user account created for
them.  This is intended only for testing, and to make the installation
go a bit smoother.  You should remove them before moving into a
production environment.

Remove anonymous users? [Y/n] <-- ENTER
 ... Success!

Normally, root should only be allowed to connect from 'localhost'.  This
ensures that someone cannot guess at the root password from the network.

Disallow root login remotely? [Y/n] <-- ENTER
 ... Success!

By default, MySQL comes with a database named 'test' that anyone can
access.  This is also intended only for testing, and should be removed
before moving into a production environment.

Remove test database and access to it? [Y/n] <-- ENTER
 - Dropping test database...
 ... Success!
 - Removing privileges on test database...
 ... Success!

Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.

Reload privilege tables now? [Y/n] <-- ENTER
 ... Success!

Cleaning up...

All done!  If you've completed all of the above steps, your MySQL
installation should now be secure.

Thanks for using MySQL!

[root@server1 tmp]#