If you have, a password protected grub boot loader and you forgot both root and grub password, then you can recover grub-boot loader password using the following method/procedure:
* Use Knoppix cd
* Remove the password from Grub configuration file
* Reboot the system
* Change the root password
* Setup new Grub password if required (optional)
You may delete a file called /etc/shadow. If you try to boot into a single user mode, system will ask for the maintenance root password. Now imagine this, you do not have a backup of /etc/shadow file. How do you fix such problem in a production environment where time is a critical factor? I will explain how to recover a deleted /etc/shadow file in five easy steps.