Overview
When the forgotten root user password, you can not log on Linux systems to perform administrative and maintenance tasks, and can only log on using some restricted features by other users. Of course, if there are other system users with root privileges, or have permission to change the root user account password, you can use these users log in and reset the root user password /
However, most of the time with a Linux host only a user with root privileges, and therefore need other ways to reset the root account password. Single-user mode by modifying the GRUB boot parameters when it is the easiest way to turn, another approach is to use the installation CD into the emergency mode.
Operating procedures
And MBR sector, GRUB repair process, like to see more blog
