A simple set of instructions to rename the normal user and change both of the factory default passwords is:
* Reboot (this is just to ensure all background processes belong to the user are not running... there are other ways to achieve this but this way is easy)
* Once the machine reboots press Alt-Ctrl-F1 to being up a text terminal
* Login as root. login: root password: root
* Set a strong password for the root user: passwd (and follow prompts)
* Rename the rock user to your prefered username (replace myself with whatever you like): usermod -l myself -d /home/myself -m rock
* Rename the rock group to match your preferred username: groupmod -n myself rock
* Set a strong password for the normal user: passwd myself
* Log out of the text termainl: logout
* Press Alt-Ctrl-F7 to go back to the login screen and then login as the normal user
* Reboot (this is just to ensure all background processes belong to the user are not running... there are other ways to achieve this but this way is easy)
* Once the machine reboots press Alt-Ctrl-F1 to being up a text terminal
* Login as root. login: root password: root
* Set a strong password for the root user: passwd (and follow prompts)
* Rename the rock user to your prefered username (replace myself with whatever you like): usermod -l myself -d /home/myself -m rock
* Rename the rock group to match your preferred username: groupmod -n myself rock
* Set a strong password for the normal user: passwd myself
* Log out of the text termainl: logout
* Press Alt-Ctrl-F7 to go back to the login screen and then login as the normal user