How to rename MySQL users without logging into MySQL?
You will have to due it the sneaky way

STEP 01 : Restart mysqld without grants and with no one being able to login behind you

$ service mysql restart --skip-grant-tables --skip-networking


STEP 02 : Login to mysql passwordless

$ mysql


STEP 03 : Locate all users in mysql you want to change

EXAMPLE: Suppose the user in question is olduser and you want to changed to newuser

Run this

mysql&gt; SELECT user,host FROM mysql.user WHERE user='olduser';


to user all users run this

mysql&gt; SELECT user,host FROM mysql.user;


You can change the username with the following

mysql&gt; UPDATE mysql.user SET user='newuser' WHERE user='olduser';


STEP 04 : Leave mysql when you have changed all users you needed to change

mysql&gt; exit


STEP 05 : Restart mysqld normally

$ service mysql restart