I had a similar issue. Assuming you are using the default grub loader, as the system boots up, just past POST you will see the grub load start and it gives you a few seconds to hit the escape key to interupt the boot up process. Hit Escape, then it list the different boot options, highlight the kernel, hit e, this will allow you to edit that line, type single at the end of what is already there, then hit enter and it will bring you back to the list of boot options , make sure the kernel is still highlighted and hit b to boot that. It won't ask for any password, it will just bring you to a terminal. Here you can change the root password by typing passwd. And you can create a new user by doing adduser. If you already have a user that you want to change the password for type passwd username, but don't type "username", use a real user you created like Indra.
Hope this helps.