I am using MySQL-Server over CentOS. I 'yum remove' the MySQL-server and on the other hand 'yum install' it. After I attempted establishing a brand new password for 'root' using 'mysqladmin'... it elevated a mistake. Some following up demonstrated still it had earlier-installation's root credential working for this.

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Trying more stuff, I by hand set 'old_password=0' in '/etc/my.cnf' after which attempted re-setting up. Still it had the sooner password working for this.

Seems like the mysql tables aren't being removed/changed when removing/setting up. I don't know where they're situated on CentOs (/var/lib/mysql?), but when you remove these by hand, it will work.