If you need to reset the root password on a Linux box running the GRUB boot loader:
- During boot, hit Tab, and GRUB should permit you to see the boot option lines.
- Edit one of them. Replace
ro quiet splashwithrw init=/bin/bash. - Boot without saving the line permanently. The system will send you directly into single-user mode as root, from where you can run ‘passwd’ to change it.