In case you have forgotten your root password for MySQL database, you can change it by first killing all mysql processes with:
killall mysql or /etc/init.d/mysql stop (for Debian users)
Now you have to start mysql again with this command:
mysqld --skip-grant-tables &
After you tried to log in with root user three times and got the message “maximum number of log ins exceeded” you have to restart the computer.
On the GRUB menu, press “E” once to enable edit, and press “E” again on the kernel line to edit it. Near the end of this line change value “ro” to “rw” and add “init=/bin/bash” at the end of this line.
Now boot into Linux and you will have root shell access where you can change the password or do whatever you please.