VI. Repair grub menu
(1) Learn the location grup configuration files
1.cd /boot
2. There are grub2 and grub
grub: Start menu background image
grub2: Start menu configuration file
(2) The analog destruction grub menu
(3) .reboot restart following occurs
(4) Restart press the ESC stage reading section, according to the step proceeds to the emergency mode (connected to the optical disk system image)
(5) The input chroot / mnt / sysimage / bash into the environment
(6) Input grub2-install / dev / sda sda partition reload
(7) Input grub2-mkconfig -o /boot/grub2/grub.cfg rebuild grub menu Profile
(8) Enter exit to exit bash environment and reboot
(9) Wait for some time
grub menu repair is complete
VII. Crack the root password
When the root password is forgotten, the administrator can not operate, reset the password to enter the emergency mode
(1) in accordance with our previous method into the emergency mode (connected to the optical disk system image)
(2) Input chroot / mnt / sysimage / bash into the environment
(3) Enter passwd root to change the password
(4) Enter exit to exit bash environment, restart
(5) Use the new password root
(6). Login is successful
Such Centos root password to complete 7 crack