the KB70100 that you posted in the community tell a solution to reset "admin" account but I need to reset the "root" account so do you have a KB that explain the step?.
ps. I still can't enter to single mode by use the following steps when I was the grub menu,
Instead of adding single to the kernel line, add init=/bin/bash and hit ENTER to go back to parent menu. (ESC will revert your change!). Then hit b to boot this kernel line.
This will drop you directly into a shell. File system will be mounted read-only, so you have to make it writeable before you can reset the password.
# mount -o remount,rw /
You should see "passwd: all authentication tokens updated successfully."
Because you bypassed original init service you have to take care when rebooting the appliance as normal shutdown/reboot scripts won't work.
First make sure that all data is written to HDD with "sync", then force reboot with parameter -f:
# reboot -f
Single user mode won't help you here because it will still ask for root password.