Chapter 10 linux Emergency troubleshooting-centos7.5 knowledge

Centos7 forgot the root password

On the LINUX kernel option, press e on the first item, find the linux16 line, and finally add rd.break;ctrl+x, and then

Mount-o remount,rw / sysroot

Chroot / sysroot

Passwd-d root

Touch /. Autorelabel

Exit

Exit

Then change the password.

Or other means.

2. Set the password by GRUB

1. Modify / etc/grub.d/00_header and add: at the end of the file:

# admin grub,append by jason.wang 20181105

Cat insmod xfs

Grub > set root= (hd0,msdos1) (- > this is the boot partition you found in the previous step)

Grub > linux16 / vmlinuz-xxxxx root=/dev/mapper/centos-root

Grub > initrd16 / initramfs-.xxxxx.img

Grub > boot

If there is no problem, the system will boot normally at this time.

Repair grub

The above has entered the system, you can view the / boot/grub2/grub.cfg file at this time, it should be empty. You can fix grub with the following command.

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

Sometimes the Windows system is recognized using the sudo grub2-mkconfig command, but the configuration file / boot/grub2/grub.cfg for grub2 is not updated. Then add one more parameter-o

After the operation is complete, you can restart the confirmation.

Assignment:

1. Two ways to operate GRUB plus password

2. The solution for Centos7.5 to forget the password.