Linux operating system --------- modify password command or repair grub

The steps to modify the password are as follows:

1. Load the CD, select in the CD boot interface ----- troubleshooting
2. Enter the troubleshooting menu and select -----Rescue a centos system
3. To enter the guide, you can press enter, or wait to press 1 and press enter to enter sh-4.2#
4. Cut the root after entering rescue mode:

chroot /mnt/sysimage/

5. change Password:

 passwd root

输入密码：123123					##  1次
输入密码：123123   				##  2次

6. Restart:

exit
reboot

7. verification:

• Login: root
• Password: 123123

Just complete a simple password change operation

Repair CD files

1. Load the CD, select in the CD boot interface-----troubleshooting
2. Enter the troubleshooting menu, select ----- Rescue a centos system
3. To enter the guide, you can press enter, or wait to press 1 and press enter to enter sh-4.2#
4. Cut the root after entering rescue mode:

 chroot /mnt/sysimage/

5. Use the grub2-install command to repair grub-----------------------------###It is not good to use the 7 and 8 commands

grub2-install /dev/sda

6. Check if it is repaired:

cd /boot/grub2/

7. Use the grub.cfg configuration file:

grub2-mkconfig -o /boot/grub2/grub.cfg

8. Check if it is repaired:

cd /boot/grub2/

9. Restart:

exit
reboot 

Finish changing the hard disk to the priority startup item